Around 225,000 people develop dementia every year – that’s the equivalent to one person every three minutes. This September and October Memory Walks will be taking place across England, Wales and Northern Ireland to raise money for a world without dementia. Arm in arm, step by step and pound by pound, we will get there. Once you donate, Just Giving will send your money directly to the Alzheimer's Society. So it’s the most efficient way to raise money – saving time and cutting costs for the charity. Please dig deep and help us walk for a world without dementia.
On October 3rd I will be taking part in one of the memory walks to raise money and show my support, if you wish to sponsor me or donate you can do so using the link below. Thank you for your support
https://www.justgiving.com/MW15alicematkin
For more information on the event please see: https://www.memorywalk.org.uk/
Alice's Design Blog
Wednesday, 12 August 2015
Thursday, 19 March 2015
Tuesday, 10 March 2015
Unit 29 Contribute ideas to production
Identify sources of
ideas for productions, explaining how these can be accessed.
There are many
different things you could use for sourcing ideas for production. For example
if I was brainstorming for brochure ideas I may look to the internet, look at
previous brochures or flyers for that specific client to see what has been done
for them before or use the internet and our archives to see what other clients
have had for similar purposes and what I feel the client may like to see or
what may interested them.
Suggest ideas for
format, budget, style and potential audience for a specific
production.
When involved in meetings
with my colleagues to pass ideas around and discuss them, one of the main
factors to consider is whether the idea could actually be done, whether we have
enough time and budget to support it and that it fits its purpose well. I have
had a go at creating brochures for our company’s services as part of my job and
I have taken into consideration all these aspects to allow for a well thought
out idea that can be used and executed well for its purpose.
Identify strengths
and limitations of own ideas.
When coming up with
Layout ideas I’m good at creating lots of different appealing ideas but It is
necessary for me to ensure that what I’m planning is not only interesting for
me but will be interesting for my target audience as I’m not the target
audience I like to ask for feedback from my colleagues as we all have a
different opinion. For example during a recent project, I was re designing our
training brochure so that is was a lot less pages and so that it looked more
appealing. I printed off a few versions and gave them to people to scribble their
thoughts and opinions on, this proved to be very helpful as it gave me the
ability to create something that would appeal to a wider range of people.
Review ideas to confirm whether
there is adequate content to make a workable programme and to ensure that
they contribute towards achieving organisation objectives.
At multiple different
stages in the process I printed off a few versions and gave them to people to
scribble their thoughts and opinions on, I would also ask colleagues to give
the text a quick read to see if it had the correct spellings and punctuation.
Identify any
changes needed to meet production requirements and editorial policy.
Any changes that
need to be made are spotted at the multiple stages that I ask my colleagues for
feedback, such as at when the document gets read and when the images are
checked at the beginning to ensure they are the correct ones. When creating any
form of document it is important that you bear in mind that anyone who has also
been assigned to that specific job can edit your document for purposes such as
something being irrelevant, spelt incorrectly or changing their mind about an
image etc.
Write realistic and
clear outline proposals.
Write realistic and
clear detailed treatments, to meet schedule and budget requirements.
When being briefed
in on any project, the key is to have a clear understanding of what you want to
achieve and in what time period. To help me do this I make sure all aspects are
realistic, such as asset and artwork creation times, my deadline and the
budget. This helps me focus on what I need to achieve and by when. For example on
a Keepmoat job I would take how many house types they require and divide that
by the allocated 2D time that has been
paid for then I would take each slot of time for one house and work out what
they need creating, what I can pull from previous jobs Etc. And divide my time accordingly.
I take all these
factors into consideration for all projects when I need to. Doing things like
creating assets that aren’t required until the end while you are waiting for
assets from others helps all of the project team to produce things without
limiting the quality and it helps everyone in the team reach their own goals
and deadlines by pulling your own weight. For example I can create the draft
layout of a graphics board and sales leaflet for a house that features all the
details of a house before I have received the image created by another team
member.
Suggest named
presenters, performers or contributors to be used for the production.
This doesn’t apply
to me in my job role but if I were to do this I would talk with my colleagues
to determine the best people for this role from a perspective of everyone that
is involved.
Present ideas
clearly and cogently to relevant parties.
During projects a
number of meetings are called to discuss progress and different Concepts.
During these we present and discuss our ideas within the team and how we could
go about achieving it. The ideas are discussed around the team. This can
sometimes involve other parties outside of the immediate team, like Clients or
other companies that we may be working in collaboration with.
Identify key legal
and ethical implications which affect the use of information in production.
Comply with
relevant legal and regulatory requirements.
Certain information
has parameters and limitations and for ethical reasons it is sometimes
inappropriate or illegal to share this information. In the industry I work in the
use of information to be published without consent or the use of images without
consent, is not permitted. When using any form of image or information that has
been sourced from anywhere other than within your team you must ensure you have
the rights to use the images. In some cases you may need to pay to use the
information or images. Any information, such as photography not generated
inside the company have to comply with regulations and requirements put in
place ensuring that all uses of outside media are legal, and follow copyright.
This means any images used have to have their photographer/creator
acknowledged, no adjustments to the original images and used in an ethical way.
Wednesday, 4 March 2015
unit 38 - colour theory and colour management
Colour
theory
Basically colour theory is about how colour
works Although every bit of knowledge counts, there are three areas you should
pay particular attention to: understanding how additive and subtractive mixing
works, understanding the gamut (remember – a colour spectrum of the device) and
handling the colour wheel and harmonies.
These three things alone will give you skills
necessary to cope with any colour challenge.
Colours come in harmonies
Basic colour harmonies.
Harmonies are created by picking
colours from the wheel according to predefined schemes, such as analogous,
complementary or triad. These combinations always look balanced, natural and
eye pleasing, just as certain note harmonies in music.
Colour wheels
First invented by Sir Isaac Newton and
later improved by countless others, colour wheel shows how primary colours
blend to create other distinct hues.
Left: traditional (Newtonian) colour wheel consisting of 12 hues
created by mixing three primary colours. Right: a fancy computer
generated colour wheel based on same principles.
Traditionally, the colour wheel
consists of:
- Primary
colours: Typically
Red, Yellow and Blue.
- Secondary
colours: Green,
orange and purple hues created by mixing primary colours
- Tertiary
colours: Further
colour hues you get by mixing a primary colour with a secondary colour.
They are usually named with two words: blue-green, red-violet,
yellow-orange.
A colour wheel helps you quickly grasp
how colours relate to each other and which combinations work best through
colour wheel harmonies.
Colour models
“Teal blue” and “Fuxia” are great when
you’re talking about sweaters but having a colour name for millions of colours
we use today would be hardly practical.
That’s why we invented colour models or
standards which help us describe colours.
Using HSB colour model in Photoshop will make working with colour
easier, as this colour model was invented to help people work
more intuitively.
The RGB model
By far the most “popular” additive
colour model. Each colour is described as set of Red, Green and Blue
values on a scale from 0 to 255.
The HSB model (or HSL / HSV)
This colour model is based on RGB but
is better suited to artists and designers. Each colour is described as a
combination of Hue, Saturation and Brightness values which allows for quick and
intuitive colour choices.
For example, in HSB model, making an
orange colour brighter or darker is a matter of playing with the Brightness
slider. In RGB model, you’d have to move around all sliders to find a darker
tone of the same colour, with no clear idea on what you need to do.
The CMYK model
This is standard subtractive, printing
colour model. Each colour is represented by a corresponding value of
cyan, magenta, yellow and black inks, on a scale from 0% to 100%.
Creating colours
Human race loves to fiddle with
everything and colour is no exception.
During our exploration of colour
theory, we’ve found there are two ways to go about colour creation: by
mixing light (or additive) or by mixing paint on paper (subtractive).
Mixing light, or additive model, is
perhaps the most intuitive one. It allows you to create colours by mixing red,
green and blue light sources in various intensities. The more light you add,
the brighter the colour mix becomes, which is the reason this mixing process is
called “additive”.
Essentially, this is the way we
physically perceive colours, and the way we are accustomed to mixing colours
through RGB computer model.
Colours are mixed either by combining light sources, or paint on
paper.
But just a few decades ago, subtractive
colour mixing was the norm and it’s still being taught at art schools. In this
case, “subtractive” simply refers to the fact that you subtract the light from
the paper by adding more colours.
Traditionally, the primary colours used
in subtractive process were red, yellow and blue, as these were the colours
painters mixed to get all other hues. As printing emerged, they were
subsequently replaced with cyan, magenta, yellow and black (CMYK), as this colour
combo enables printers to produce a wider variety of colours on paper.
So when you think about it, additive
and subtractive colour models are just two sides of the same coin, or two ways
to think about the same thing – making colours.
Humans are trichromats
If you ever thought RGB colour model is
a recent discovery from Silicon Valley, you’d be three centuries off target.
The trichromatic theory – you know, the
story saying we see colours through red, green and blue channels – was given
birth in 17th century
by Thomas Young. I guess they probably considered him mad at the time.
We are able to see colours because of red, green and blue receptor
cells in our retina.
Eventually, science proved he was
completely right and explained that we are able to see the colours because we
have three distinct types of receptor cells in our retina, each being sensitive
to different light properties , or specifically, to red, green and blue colour.
Based on that and some other
experiments, scientists estimate that we are able to see approximately 10
million different colours.
Colour doesn’t actually exist.
Colour is created only when our brain
tries to make sense from light signals it receives from the outer world.
In other words, it’s all in your head.
Deprived of colour, our world would probably look like a scene from
Matrix.
Without that, our world is a monochromatic
place bathing in electromagnetic radiation of varied intensity and wavelengths.
No single device is capable of reproducing all
visible colours
“A device that is able to reproduce the
entire visible colour space is an unrealized goal within the engineering of
colour displays and printing processes”.
This is how Wikipedia explains this
problem and if you ever had issues trying to match colours on screen with those
on paper, you probably have your own words for it.
Technically speaking, every device and
printing process has its own colour gamut, or a set of
colours it can successfully reproduce.
Same
photo, as seen by computer screen (RGB) and typical printer (CMYK). As
printer cannot reproduce bright saturated tones, the colours can never
perfectly match.
In other words, your colour options are
limited depending on what you’re working with.
If you’re using RGB screens, you can
mix some very bright and saturated colours. If you have to print that
out, your options get reduced to a limited colour spectrum of a CMYK printer.
And, if you saw a brochure printed with a beautiful Pantone colours, you’ll
never be able to find them on screen they simply cannot be reproduced by RGB
monitor.
A different device means different
colours. You’ll never be able to match them perfectly but you can do a lot with
some basic colour management.
Colour Management.
After it was introduced in the early 2000s
and popularized by Apple’s ColorSync system-level software, ICC colour
management, or calibrated workflow, was embraced by various segments of the
graphic arts industry—some faster than others. The large-format printing
industry was quick to adopt colour management as a way of coming to grips with
the wide variety of printers, inks, media, RIPs, and settings. Likewise,
photographers, whose darkrooms got replaced with inkjet printers, quickly
appreciated the potential for accurate on-screen previews and matching output.
What Is Colour Management?
Colour management uses
industry-standard ICC profiles to characterize the colour of different
production devices, including digital cameras, monitors, printers, and
proofers. Due to the plug-and-play nature of desktop publishing, colour cannot
be expected to match from one device to another, especially when they use
different colorant systems (e.g., RGB vs. CMYK) and a multitude of colorants.
Given a set of ICC profiles and workflow software, such as Photoshop or a RIP,
colour-managed workflow attempts to match colour as closely as possible among
different devices.
Why Do You Need It?
Commonly cited reasons for interest in
colour management include:
1. Consistency. A key word in the
graphic arts, consistency means the ability to get colour correct “the first
time, every time” (to quote the famous rice commercial) — and also to get
colour that matches throughout a print run and from run to run.
2. Soft proofing. Monitor previews that
match printed output are referred to as soft proofs. Contrary to popular
belief, a calibrated monitor does not necessarily guarantee a match with
printed colour. It only shows that “what you see is what’s in the file”
(WYSIWIF). For accurate soft proofs, both a printer and monitor profile are
required, along with a “proofing” or “simulation” workflow.
3. Hardcopy proofs. Clients want to see
proofs that match production prints. Whether you are printing digital, offset,
large format, or using another process, proofs refer to pre-printed samples
that show how production prints will look. They are generally printed on
faster, lower cost, and easier-to-operate printers, such as inkjet, which may
not inherently match the production process.
Some
additional interests in colour management:
4. Calibrated captures. These are
digital photos that match the original scene or object. This could be
especially important in catalogue and product photography. Also, what if a
large job is farmed out to several photographers, how could it be assured that
all of their results will match?
5. Standardized files. Digital cameras
that capture JPEG format can output to standard profiles, generally RGB and the
larger-gamut Adobe RGB. Having all job files in the same colour profile ensures
they will have optimum colour and match closely when output.
First born in the ivory tower, colour
management has benefited from considerable philosophical thought. However,
these principles, while they may seem academic, help guide colour management
implementation.
The four “C”s of Colour Management. The
procedures necessary to calibrate a device could be thought of as the four
“C”s:
Consistency refers to setting up a
device to achieve optimum colour. For an inkjet printer, these steps could
include setting ink limits and total ink coverage for optimum ink usage and
colour gamut.
Calibration refers to aligning all
devices to a known standard or specification. A common standard for inkjet
printers is linearization, meaning tones, or halftone dot values, increase in
sequence. This ensures consistent performance and images with good contrast and
tone separation.
Characterization means profiling a
device using a profiling program and a colour target that’s printed, captured,
or displayed.
Conversion – for colour to match from
one device to another, colours must be converted, or changed in value, to
create the match. This conversion is done by the workflow software, whether
it’s Photoshop or a RIP.
Source-destination-simulation workflow.
A model of workflow for calibrated devices, it means that each image came from
somewhere (the source, e.g., digital camera, digital file) and will go
somewhere (the destination, e.g., a monitor, printer, proofer, or even a
digital file). In addition, the simulation workflow allows the output to be
altered to match a different device. This could be true when an inkjet printer
(the destination) is used to make hardcopy proofs for a lithographic press (the
simulation).
Standard working space profiles. Apple
introduced a series of standardized monitor profiles as so-called “standard
working space” profiles. These profiles, widely available and distributed with
system software and applications, provide a standard of reference for images.
The most widely used standard working space profiles are Adobe RGB (larger) and
sRGB (slightly smaller). Others include ProPhoto RGB, ColorMatch RGB, and Apple
RGB.
Profile embedding. Once applied to
images, ICC profiles can be embedded into the image files in JPEG, TIFF, and
PDF format. The embedded profiles act like a “nametag” to show where the image
came from, such as a digital camera or a standard working space. Embedded
profiles can be read by workflow applications including Photoshop, InDesign,
and software RIPs.
Tools of the trade
The equipment and software you need
depends upon what type of production devices you want to profile.
Emissive colorimeter. This is a low
cost instrument necessary for profiling monitors. Emissive means the instrument
reads radiant light from monitors, as opposed to reflected light from prints. A
colorimeter is a colour measurement instrument that reads red, green, and blue
channels and maps colour to a mathematical model of human vision known as
CIELAB.
Emissive/reflective spectrophotometer.
Unlike a colorimeter, a spectrophotometer is a more sophisticated instrument
that reads the full spectrum of colour, from 380–720 nm in wavelength.
Readings, generally at 10 nm increments, provide a true “fingerprint” of
colour. These can be used for profiling both monitors and printers.
Spectrophotometers are available in two types:
x-scanning, or semi-automated,
instruments. Manual instruments that read one colour patch at a time are not
very productive for reading test charts with hundreds or even thousands of
colours. These instruments are designed to scan rows of colours so that a
target can be read in a few minutes. They are useful for profiling up to
several printers per day.
x/y-scanning, or fully-automated,
instrument. These instruments are designed to read an entire test chart
unattended. They are useful for profiling several printers per day, such as in
a high-volume print shop.
Colour profiling software. Profiling
software is available for monitors, digital cameras, and printers. These are
often separate modules that can be unlocked by a key code.
What You Need and How It Works
The following is an outline of the
equipment and software you need and the procedures necessary to profile
monitors, printers, and digital cameras.
Monitor
What
you need:
emissive colorimeter or
spectrophotometer for monitors
colour management software with
monitor-profiling capability
How it
works:
Software displays known colour values
that are measured by instrument.
Calibrates monitor to known contrast
(gamma) and colour balance (white point); loads calibration curve into video card.
Makes profile used by workflow software
to convert displayed colour to match that of file (destination workflow) or
printer (simulation workflow)
Printer/Proofer
What
you need:
reflective
spectrophotometer—fully-automated (x/y-scanning) or semi-automated (x-scanning)
colour management software with
printer-profiling capability
How it works:
Print colour target of known values.
Measure target with spectrophotometer.
Software calculates profile that
converts file to match on printer.
Digital Camera
What
you need:
target of known values (Macbeth
ColorChecker, ColorChecker SG)
colour management software
How it
works:
Set the camera’s exposure and white
balance to get a good capture of the colour management target.
Software compares captured colour
values with those on target.
Creates profile for camera.
Workflow software converts captured
colour to closer match to original subject.
The same profile can be used for
different lighting conditions, provided that the camera is white-balanced for
each.
Colour matching really comes into play
when an image is output from one process to another, whether from digital
camera to standard working space, from file to display, or from file to print
or proof. Apps could be divided into two categories:
File Creation apps. Applications for
creating or editing images, illustrations, or pages. Photoshop, InDesign, and
Illustrator are all ICC compliant and support colour-managed workflow. These
programs can read embedded ICC profiles, render colours for accurate display,
and soft-proof files to preview final output. Some of the key settings are:
Convert to profile—tells where the
image is going, i.e., converts colour (see “The four ‘C’s of colour management”)
to the output profile.
Assign profile—tells where the image
came from, i.e., digital camera or standard working space.
Read embedded profile—most applications
do this by default, however if there is no embedded profile, default profiles
can be set using either:
Colour settings—used to specify default
profiles if none are present, or,
Monitor profile—applications
automatically read the default system profile and use it without operator
intervention.
Software RIPs. Raster image processors
used to output digital files to printers and image carriers are virtually all
ICC-compliant. Look for places to specify source, destination, and (in the case
of proofing) simulation profiles.
Unit 38 - Colour management procedures, Storing images and files for future use
Digital
Image File Types.
JPG, GIF, TIFF, PNG,
BMP. What are they, and how do you choose? These and many other file types are
used to encode digital images. The choices are simpler than you might think.
Part of the reason for
the plethora of file types is the need for compression. Image files can be quite large, and larger file
types mean more disk usage and slower downloads. Compression is a term used to
describe ways of cutting the size of the file. Compression schemes can by lossy or lossless.
Another reason for the
many file types is that images differ in the number of colours they contain. If
an image has few colours, a file type can be designed to exploit this as a way
of reducing file size.
Lossy vs. Lossless compression
You will often hear the
terms "lossy" and "lossless" compression. A lossless
compression algorithm discards no information. It looks for more efficient ways
to represent an image, while making no compromises in accuracy. In contrast,
lossy algorithms accept some degradation in the image in order to achieve
smaller file size.
A lossless algorithm
might, for example, look for a recurring pattern in the file, and replace each
occurrence with a short abbreviation, thereby cutting the file size. In
contrast, a lossy algorithm might store colour information at a lower
resolution than the image itself, since the eye is not so sensitive to changes
in colour of a small distance.
Number of colours
Images start with
differing numbers of colours in them. The simplest images may contain only two
colours, such as black and white, and will need only 1 bit to represent each
pixel. Many early PC video cards would support only 16 fixed colours. Later
cards would display 256 simultaneously, any of which could be chosen from a
pool of 224, or 16 million colours. New cards devote 24 bits to each
pixel, and are therefore capable of displaying 224, or 16 million
colours without restriction. A few display even more. Since the eye has trouble
distinguishing between similar colours, 24 bit or 16 million colours is often
called True Colour.
The file types
TIFF is, in principle, a very
flexible format that can be lossless or lossy. The details of the image storage
algorithm are included as part of the file. In practice, TIFF is used almost
exclusively as a lossless image storage format that uses no compression at all.
Most graphics programs that use TIFF do not compression. Consequently, file
sizes are quite big. (Sometimes a lossless compression algorithm called LZW is
used, but it is not universally supported.)
PNG is also a lossless
storage format. However, in contrast with common TIFF usage, it looks for
patterns in the image that it can use to compress file size. The compression is
exactly reversible, so the image is recovered exactly.
GIF creates a table of up to
256 colours from a pool of 16 million. If the image has fewer than 256 colours,
GIF can render the image exactly. When the image contains many colours,
software that creates the GIF uses any of several algorithms to approximate the
collars in the image with the limited palette of 256 colours available. Better
algorithms search the image to find an optimum set of 256 collars. Sometimes
GIF uses the nearest colour to represent each pixel, and sometimes it uses
"error diffusion" to adjust the colour of nearby pixels to correct
for the error in each pixel.
GIF achieves compression
in two ways. First, it reduces the number of colours of colour-rich images,
thereby reducing the number of bits needed per pixel, as just described.
Second, it replaces commonly occurring patterns (especially large areas of
uniform colour) with a short abbreviation: instead of storing "white,
white, white, white, white," it stores "5 white."
Thus, GIF is
"lossless" only for images with 256 colours or less. For a rich, true
colour image, GIF may "lose" 99.998% of the colours.
JPG is optimized for
photographs and similar continuous tone images that contain many, many colours.
It can achieve astounding compression ratios even while maintaining very high
image quality. GIF compression is unkind to such images. JPG works by analysing
images and discarding kinds of information that the eye is least likely to
notice. It stores information as 24 bit colour. Important: the degree of
compression of JPG is adjustable. At moderate compression levels of
photographic images, it is very difficult for the eye to discern any difference
from the original, even at extreme magnification. Compression factors of more
than 20 are often quite acceptable. Better graphics programs, such as Paint
Shop Pro and Photoshop, allow you to view the image quality and file size as a
function of compression level, so that you can conveniently choose the balance
between quality and file size.
RAW is an image output
option available on some digital cameras. Though lossless, it is a factor of
three of four smaller than TIFF files of the same image. The disadvantage is
that there is a different RAW format for each manufacturer, and so you may have
to use the manufacturer's software to view the images. (Some graphics
applications can read some manufacturer's RAW formats.)
BMP is an uncompressed
proprietary format invented by Microsoft. There is really no reason to ever use
this format.
PSD, PSP, etc are proprietary formats
used by graphics programs. Photoshop's files have the PSD extension, while
Paint Shop Pro files use PSP. These are the preferred working formats as you
edit images in the software, because only the proprietary formats retain all
the editing power of the programs. These packages use layers, for example, to
build complex images, and layer information may be lost in the non-proprietary
formats such as TIFF and JPG. However, be sure to save your end result as a
standard TIFF or JPG, or you may not be able to view it in a few years when
your software has changed.
Currently, GIF and JPG
are the formats used for nearly all web images. PNG is supported by most of the
latest generation browsers. TIFF is not widely supported by web browsers, and
should be avoided for web use. PNG does everything GIF does, and better, so expect
to see PNG replace GIF in the future. PNG will not replace JPG, since JPG is capable of much greater
compression of photographic images, even when set for quite minimal loss of
quality.
File size comparisons
Below are comparisons of
the same image saved in several popular file types. (Note that there is no
reason to view more than one of the TIFFs or the PNG. Since all are lossless
formats, their appearance is identical.)
File type
|
Size
|
|
Tiff, uncompressed
|
901K
|
|
Tiff, LZW lossless compression.
|
928K
|
|
JPG, High quality
|
319K
|
|
JPG, medium quality
|
188K
|
|
JPG, my usual web quality
|
105K
|
|
JPG, low quality / high compression
|
50K
|
|
JPG, absurdly high compression
|
18K
|
|
PNG, lossless compression
|
741K
|
|
GIF, lossless compression, but only 256
colours
|
286K
|
When should you use each?
TIFF
This is usually the best
quality output from a digital camera. Digital cameras often offer around three
JPG quality settings plus TIFF. Since JPG always means at least some loss of
quality, TIFF means better quality. However, the file size is huge compared to
even the best JPG setting, and the advantages may not be noticeable.
A more important use of
TIFF is as the working storage format as you edit and manipulate digital
images. You do not want to go through several load, edit, save cycles with JPG
storage, as the degradation accumulates with each new save. One or two JPG
saves at high quality may not be noticeable, but the tenth certainly will be.
TIFF is lossless, so there is no degradation associated with saving a TIFF
file.
Does NOT use TIFF for
web images. They produce big files, and more importantly, most web browsers
will not display TIFFs.
JPG
This is the format of
choice for nearly all photographs on the web. You can achieve excellent quality
even at rather high compression settings. I also use JPG as the ultimate format
for all my digital photographs. If I edit a photo, I will use my software's
proprietary format until finished, and then save the result as a JPG.
Digital cameras save in
a JPG format by default. Switching to TIFF or RAW improves quality in
principle, but the difference is difficult to see. Shooting in TIFF has two
disadvantages compared to JPG: fewer photos per memory card, and a longer wait
between photographs as the image transfers to the card. I rarely shoot in TIFF
mode.
Never use JPG for line
art. On images such as these with areas of uniform colour with sharp edges, JPG
does a poor job. These are tasks for which GIF and PNG are well suited.
See JPG vs. GIF for web images.
GIF
If your image has fewer
than 256 colours and contains large areas of uniform colour, GIF is your
choice. The files will be small yet perfect. Here is an example of an image
well-suited for GIF:
Do NOT use GIF for
photographic images, since it can contain only 256 colors per image.
PNG
PNG is of principal
value in two applications:
- If you have an image with large areas of
exactly uniform colour, but contains more than 256 colours, PNG is your
choice. Its strategy is similar to that of GIF, but it supports 16 million
colours, not just 256.
- If you want to display a
photograph exactly without
loss on the web, PNG is your choice. Later generation web browsers support
PNG, and PNG is the only lossless format that web browsers support.
PNG is superior to GIF.
It produces smaller files and allows more colours. PNG also supports partial transparency. Partial
transparency can be used for many useful purposes, such as fades and
antialiasing of text. Unfortunately, Microsoft's Internet Explorer does not
properly support PNG transparency, so for now web authors must avoid using
transparency in PNG images.
Other formats
When using graphics
software such as Photoshop or Paint Shop Pro, working files should be in the
proprietary format of the software. Save final results in TIFF, PNG, or JPG.
Use RAW only for
in-camera storage, and copy or convert to TIFF, PNG, or JPG as soon as you
transfer to your PC. You do not want your image archives to be in a proprietary
format. Although several graphics programs can now read the RAW format for many
digital cameras, it is unwise to rely on any proprietary format for long term
storage. Will you be able to read a RAW file in five years? In twenty? JPG is
the format most likely to be readable in 50 years. Thus, it is appropriate to
use RAW to store images in the camera and perhaps for temporary lossless
storage on your PC, but be sure to create a TIFF, or better still a PNG or JPG,
for archival storage.
Choosing a File Format for Digital Still Images
The choice of file
formats can often prove overwhelming for someone new to the world of digital
imaging. The aim of this document is to explain some of the factors that should
be considered before choosing a format and suggest suitable file formats for
specific applications.
Over the years, there
have been a number of file formats that have been proposed and used. Every
year, this choice gets larger and larger as new file formats are introduced and
it is not always immediately clear which is the best one to use in any
particular case. The choice will depend on a number of factors, which will vary
according to the type of media and how you intend to use the file. Each stage
of the process, from capture through to delivery, has its own requirements that
may affect this choice.
This report provides a
brief look at some of these factors and provides guidelines to making the best
choice from what is available.
For a
full introduction to the file formats themselves, see the JISC Digital Media
advice document File Formats and Compression.
Choose a non-proprietary open 'standard'
Despite the large range
of available file formats, choosing one should not be too hard as only a very
few of them are normally recommended for digitisation projects. Any
digitisation project will need to consider the long-term usefulness and
accessibility of the images and this means choosing a file that is both an
established industry 'standard' as well as a non-proprietary format. This
limits the range to a much more easily considered number that includes the most
common four below:
·
TIFF (Tagged Image File
Format)
·
PNG (Portable Network
Graphics)
·
JPEG or JFIF (Joint
Photographic Experts Group File Interchange Format)
·
GIF (Graphic Interchange
Format)
There can be good
reasons why a project might wish or need to use another file format at some
part of their project, such as some of the proprietary formats including:
·
PDF (Portable Document
Format/Adobe Acrobat File)
·
PSD (Photoshop
Document/Adobe Photoshop Image File)
·
The camera's native RAW
file
However
this is likely to come about because of some specific need of a particular
project and cannot be covered here. For details of these file types and many
others, please see the JISC Digital Media advice document File Formats and Compression.
This is the first step
in the digitisation process. When capturing images, it is important that they
are all created at the highest possible quality and at a size appropriate for
all subsequent uses. Errors at this point will certainly compromise the quality
of the whole project and the only recovery option will be to go back and
re-capture the original.
All
digital capture devices originally capture values of Red, Green and Blue. The
number of different describable colours (or tones of grey) will depend upon the
'bit-depth' of the device. Any modern device will be able to capture in at
least 24-bit colour (or 8-bit B&W) (see the JISC Digital Media advice
document The Digital Still Image),
although some modern devices can capture at higher bit depths, right up to
48-bit.
Some of the more
advanced cameras offer their own un-processed RAW formats. These files contain
all of the original data as captured by the sensor without alteration. These
images are then processed on the computer where fine adjustments can be made to
the white balance, exposure and sharpness before saving in a non-proprietary
format. RAW files usually contain higher bit depths than the
equivalent JPEGs and TIFFs produced by the camera.
Once the capture device
has created the image, it must be saved for later use.
Format requirements
A file format should be
chosen that:
·
Retains all information
that was created by the capture device. This will mean using a file format that
can store the image in at least the same colour depth as it was created. 24-bit
for colour and 8-bit for B&W should be considered the minimum although
files captured with a larger bit-depth should really be archived with this
information
·
Retains any capture
device colour management information (ICC profile)
·
Uses (or can be set up
to use) no compression
The suggested format here is: TIFF or the proprietary format of
capture device.
Although it is normally advisable to avoid all proprietary file formats, there can be an argument for the temporary use of a proprietary format within the scanning software if it is able to offer some level of additional functionality. However it would still need to be converted to another open standard format before being archived.
Although it is normally advisable to avoid all proprietary file formats, there can be an argument for the temporary use of a proprietary format within the scanning software if it is able to offer some level of additional functionality. However it would still need to be converted to another open standard format before being archived.
When we mention or
specify TIFF, it is important to realise that the TIFF file
format comes in a range of types, supporting different functionality, such as
multipages and even a choice of compressions including JPEG. So when we
specify TIFF for archival purposes we always mean an uncompressed
Baseline TIFF v6 with Intel byte order (PC option).
There are two possible
methodologies for creating a Master Archive and both have advantages, depending
on the project.
Method
1 - Archive all data exactly as created by the capture device.
The
Master Archive contains a copy of each image in a form as close as possible to
the original captured data. This enables the project to go back to the archive
knowing that they have an exact copy of everything that was originally created
by the capture device for the project. It should be realised that as images are
pre-optimisation, they might not look as good as those archived using Method 2.
They will be in a totally original form but not necessarily the highest visual
quality. With this approach, it is important to use a colour space that in no
way compromises the colour gamut of the original data. This will often mean leaving
the image within the capture device's own colour space, but could mean using a
larger or unbounded colour space such as CIE Lab.
Method
2 - Archive an optimised version of image file.
The
Master Archive contains a copy of each image after it has been prepared and
optimised for use at its highest quality (see Basic Guidelines for Image Capture and Optimisation). This has the advantage of archiving the image in
a ready-to-use state. The optimisation need only be done once, and all images
can be handled in a consistent way. However, it is inevitable that some data
will have been lost in the process and if the optimisation (see Basic Guidelines for Image Capture and Optimisation) is in any way inappropriate or badly undertaken
then the project will be unable to go back to the original data and work from
there. For this approach it would make sense to save the image in a colour
space appropriate for the intended use of the image in the future.
(Adobe RGB 1998 would be advised for print/web, but sRGB could be
used if the only delivery medium was going to be the web).
Format requirements
The requirements of a
file format for archiving are the same as for creation except that it should
also:
·
Be an open standard file
format - proprietary formats should not be used, as there is uncertainty about
the ability to open the file in the future. A possible exception to this might
be the Adobe Photoshop format - see below
·
Preferably not use any
compression, although lossless compression may be acceptable. Be aware that one
of the most common lossless compressions is LZW, which is based upon patented
technology and should therefore be avoided.
·
Suggested formats:
·
Method 1 DNG, TIFF, PNG
·
Method 2 TIFF, PNG or possibly PSD
One way around the
question of whether to archive before or after optimisation is to use the
'layers' features of Photoshop and save the image as a PSD file. This
proprietary file format allows both the original image (un-optimised) and any
optimisation to be stored within the same file. This effectively allows both
states of the file to be archived within the same file. The PSD file
is however a 'Proprietary' format and its use should therefore be approached
with great care.
All image optimisation
and manipulation is undertaken within image processing software. Whilst
carrying out this work, it can be useful to save the image in the proprietary
format of the image processing software.
Editing can be a time
consuming process and the proprietary formats offer increased functionality
that enable extra information (e.g. layers, masks and channels) to be stored.
This enables subsequent editing to resume from where the last session finished
without having to recreate any prior work. Unfortunately using a proprietary
file format in this way conflicts with the preservation requirements of our
archive images. This is where archiving after optimisation can have an
advantage.
On the other hand, if
the image is going to require a lot of manipulation or will be made for a
specific use then it can be helpful to have access to the original file before
any other processing has been undertaken. This is an advantage of archiving
before optimisation.
Suggested formats: Image
processing proprietary formats such as PSD for Photoshop,PSP for
Paint Shop Pro and PNG for Fireworks. However TIFF is still
a good choice if the increased functionality of the proprietary formats are not
required (the TIFF format can save some layer information but only a
few programs such as Photoshop CS can read this information - so it can no
longer be considered a truly open source file).
However, once the image
manipulation has been finished the file should be saved in a form appropriate
to its subsequent use.
Choosing the correct
image file format for delivery probably poses the hardest decision with the
biggest variety of choice. These are just some of the issues that will need to
be considered:
·
What is the intended use of the image
after delivery?
·
How much image resolution is needed
to convey the intellectual content to the user?
·
On what output device is the image
going to be used - monitor, printer, projector?
·
What are the capabilities of the output device?
What bit depth can it handle? What is the required resolution?
·
What bandwidth is available for
delivery?
·
Is the image for photo-realistic or presentation use?
·
How is the image going
to be delivered? CD-ROM, tape, WAP,
Internet (dialup, broadband, LAN or WAN connection)?
·
Is there a requirement
to add any watermarking or deal with
any other digital rights management issue?
·
Do the users require the
image to be provided with any colour profile or other colour management
information?
With so many
considerations, combined with the proliferation of file formats, each designed
for a specific use, it is little wonder that this subject continues to confuse
and engender debate.
With this in mind, the
following are more in the form of ideas for consideration than guidelines.
It is hard to give
generic advice in this area, the important thing is to talk to the person doing
the printing as mistakes can be costly and it is the printer who should
understand what must be provided for the agreed use. They will hopefully be
able to give you specific image preparation guidelines so as to help you
prepare images correctly for their workflow.
Normally the printer
will want images in a high quality uncompressed format such
as TIFF or within an encapsulated metafile such
as EPS or PDF (although in the commercial world Quark files
are also popular as many printers have an established workflow based around
Quark XPress, which provides all layout and sizing, whilst the image is
provided as a linked TIFF).
Remember
that the printing process uses subtractive colour rather than additive colour
(see the JISC Digital Media advice document The Digital Still Image) and
this means the image must be printed from a CMYK file rather than
an RGB one. It will therefore be necessary for either you or the
printer to convert the image file from RGB to CMYK. This is
rarely an easy task and should be undertaken with care by a skilled operator
who understands the workings of a CMYK printing workflow. Due to
problems with this process, it is becoming more common to provide the printer
with an RGB file and ask them to undertake the transformation. When
this is done, it is normal to use an RGB colour space that is
designed to transform to CMYK easily. There are a few possibilities,
but the most common and almost standard is Adobe RGB 1998.
Suggested formats: TIFF (RGB), TIFF (CMYK), EPS, PDF
It is quite normal to
have to undertake a fair amount of testing and adjusting with a desktop printer
before it is possible to get the best results out of it. Most of these devices
(certainly all those using ink/pigment) print in CMYK, however they
normally undertake the conversion themselves and have been designed to work
best with RGB data. The exceptions to this are 'continuous tone'
printers such as the dye sublimation and photo-printer types which print in RGB.
The normal desktop
printers (ink-jet and colour photocopier) are designed to work happily with a
range of image file formats, including JPEG compressed files. However
they will still work best with the maximum amount of image data supplied by an
uncompressed image such as a TIFF or PSD. Nonetheless,
surprisingly good results can be obtained from JPEG compressed files as
long as the quality is set at the highest setting (with a file size larger than
10% of original).
Suggested formats: TIFF (RGB), PSD, JPEG (high
quality setting)
For most digitisation
projects, the most common delivery format is simply a monitor with the images
viewed through a web browser interface. This makes the choice of file format
easy as the current selection of web browsers only support a small range of
image file formats (JPEG, GIF & PNG), although this range
can be extended with the use of the appropriate plug-in.
Delivering images
through a web browser has some inherent advantages and unfortunately some
challenges. The main advantage is that (in common with all monitor delivery)
images naturally look 'good' on a monitor where their perceived 'brightness'
(the light is being transmitted to you, rather than reflected) hides many small
deficiencies in quality that would compromise quality if the image was printed.
On the other hand, present browsers have only limited image-viewing
capabilities and are unable to 'zoom' in and out of the images. This means that
delivery is limited to images with pixel dimensions that fit within the user's
browser - suggested standards at present are to design web pages to a size of
800 x 600 pixels giving standard image sizes of approx 512 pixels on the
longest edge.
The largest limitation
on the quality of images delivered on the web and the main influence on
'choice', is the need for them to be compressed to a size that makes their
delivery over the limited available bandwidth possible. All the file formats
supported by web browsers provide compression, however the amount and method of
compression varies.
Web browsers currently
support the following file formats:
·
JPEG (JFIF)
- JPEG is not actually a file type, but a type of compression
proposed by the Joint Photographic Experts Group. It is used within the JFIF
file format that uses the file extension .jpg and we colloquially call the
'JPEG'. It is a lossy compression and will provide the best quality and lowest
file size for continuous tone images. The amount of compression given to the
file is chosen at the time of saving the file and allows for variation in
quality against file size: as a rule of thumb, it is normally considered that a
file compressed with JPEG to 10% of its original size will be
visually acceptable with no obvious compression artefacts. However it is common
if required, to compress right down to 2-4% if the lower quality is acceptable.
·
GIF - The Graphic
Interchange Format, is an 8-bit (and under) indexed file type only offering a
range of 256 (or less) different colours (these can either be a standard
selection or a image-dependent selection by user-choice). It was designed in
the early days of the Internet by CompuServe and works best for use with simple
images using block colours, such as graphics, logos and
banners. GIF uses lossless LZW compression, the amount of compression
will depend totally on the type of image being saved. A full colour continuous
tone image is unlikely to compress to less than 30% of its original size,
however a solid colour vector image should compress far more. The GIF file
format supports layers allowing it to offer both transparency and animation.
·
PNG - The Portable
Network Graphics (colloquially called 'PING') file is an open source 'standard'
that was introduced to overcome the possible patent problems associated with
the GIF format (the LZW patent expired in 2004). It is normally used
in either an 8-bit indexed version or as a 24-bit full colour version, although
there is also an infrequently used 48-bit version as well. This makes it a very
versatile format offering either the advantages of lossless compression in full
colour (as an archive format) or as a GIF replacement in 8-bit form.
However it cannot compete with the JPEG in terms of producing high
quality and small, full colour images for viewing on the web. The compression
available from PNG in 24-bit mode is typical for a lossless
compression providing a file of about 60-75% of the original size and in 8-bit
mode it is much the same as GIF. PNG supports transparency (even
variable opacity) but is not able to provide animation.
·
The JPEG 2000
(j2k or jp2) format was developed to replace the popular JPEG format;
it makes use of wavelet compression, which can use either lossless or lossy
methods of compression. While it doesn't offer any significant increase in
compression ratios over normal JPEG there is less of the blockiness
and artifacting associated with standard JPEG compression. While JPEG2000
is not as widely supported as was first hoped, it is slowly gaining in
popularity however; it looks unlikely that it will replace JPEG in
the near future.
Suggested formats and relevant uses: JPEG, PNG, GIF
It is quite legitimate
to use any of these file formats for web delivery, however they do have
particular strengths and weaknesses that should be considered in your choice.
The table below sets out some of the more common needs, the best choice and the
reason for making your choice:
Need or Use
|
Recommended File Type
|
Reason
|
Normal continuous-tone full colour image at
the highest quality
|
JPEG or PNG
|
PNG will allow you to deliver an image
at the highest quality using lossless compression. However file size will be
very large (approx 60% of original). JPEG at its best quality
setting, should be visually identical but provide a larger compression
(approx 10-25% or original).
|
Normal continuous-tone full colour image at
highest compression
|
JPEG
|
JPEG will allow compression of the
image down to approx 2-4% of the original size. At this compression,
quality is likely to suffer, but in some cases this can be acceptable
|
A web banner or logo with 8-bit or less
colour
|
PNG or GIF
|
Both PNG and GIF offer
the best compression for file size. PNG is 'patent' free, but might
have problems with older browsers
|
Continuous-tone greyscale image
|
JPEG, PNG orGIF
|
As greyscale is only 8-bit anyway, all of
the formats should provide comparable quality, however JPEG is
likely to provide highest compression (with corresponding drop in quality)
|
Black and White bi-tonal images
|
PNG or GIF
|
In this
case, GIF or PNG should provide equal
quality. JPEG is not recommended as it will give a file size larger
than PNG/GIF due to it being unable to store less than 8-bit
greyscale
|
Image or logo with transparent layers
|
PNG or GIF
|
Both PNG and GIF support
transparency. PNG is non-patented. PNG also offers
multi-layers and variable-transparency. Note this is not supported in older
browsers
|
A full colour image with lossless
compression
|
PNG
|
As stated above, only PNG allows
you to deliver a losslessly compressed image
|
Animated image
|
GIF
|
At present only GIF can support
animation
|
A zoomable or streamable image
|
JPEG, JP2,VFZ
|
This will largely depend upon server
software, however it is hoped that browsers will be able to provide this with
newer file types such as JPEG 2000 or VFZ
|
A file with reliable image metadata tagging
|
JPEG, PNG, JP2
|
At present this is not supported by the
current web browsers, however JPEG and PNG both do
support IPTC data. JPEG 2000 also has an XML-based
inbuilt metadata system, which should hopefully be readable by future web
browsers
|
A file with integral rights management
|
VFZ, JP2
|
So far all these systems will need some
server-side software and plug-ins within the user's browser, however again it
is hoped that JPEG 2000 and next generation browsers will be able
to provide this functionality
|
File formats for PowerPoint or other multimedia
programs
As
long as the intended delivery format is still using a monitor, all the file
formats recommended for use within a web browser will still be good choices.
However if MS PowerPoint is being used to create posters or some other printed
media, it might well be better to consider some of the image file formats suggested
in the section for Commercial printing or Desktop printing.
The main influence on
choice will be the available bandwidth for the delivery of this material. If
there are bandwidth restrictions then it will make sense to use some of the
file formats suggested for web delivery, however if the presentation is to be
delivered locally then there is no reason to not use images of a
correspondingly higher quality.
Suggested formats for monitor delivery: JPEG, PNG and GIF (at
compression rate to suit delivery bandwidth and PC performance)
Suggested formats for print delivery: JPEG - High Quality, TIFF, PNG and GIF
Suggested formats for print delivery: JPEG - High Quality, TIFF, PNG and GIF
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