Digital
Photography Standards and Practices Project:
An Overview of Terms and Procedures
All Text © Richard Anderson
Overview:
A
revolution has quietly occurred that has forever changed the
way Photography will be created, viewed, managed and printed.
This revolution is similar to the revolution that replaced paste-ups
with Quark. It will affect everyone in the chain, from client
to photographer, to agency, to designer, to offset printer.
Those
who take the time to educate themselves about the new technologies
will reap the benefits, and those who do not will find themselves
increasingly behind the curve. These benefits include greater
immediacy in seeing results, potentially faster project completion,
greater interaction between client, designer and photographer,
and, if managed properly, greater accuracy of color reproduction.
In
order to achieve these good things, a common set of digital photo
file management standards needs to be implemented by the client,
the agencies, the design firms, the photographers, and offset
printers.
Digital Capture vs. Film: Even
though digital capture is still in relative infancy compared
to film, it is rapidly replacing film as the preferred medium
for many photographers. The instant feedback is particularly
useful for corporate and advertising shoots, especially those
involving people. Heightened security at airports has made transporting
film increasingly difficult and can place entire assignments
at risk.
Film
is risky even after processing in that there is only one original
image. Once processed, film needs to be digitized by scanning.
This necessarily involves a degradation of quality because the
result is now second generation.
Resolution and File Size: There exists a great deal of confusion regarding file sizes of scanned film vs. digital capture. This is because to get equivalent quality, a film scan needs to be 2 to 3 times the file size of a digital capture. This is partly due to the second-generation nature of a scan, and it is also due to the fact that the digital information in a film scan will not all be of useful detail. For this reason, storing digitally captured images is more efficient than storing equivalent-quality film scans.
For
instance, if you scan a 35mm transparency at 4000 ppi (pixels
per inch, not to be confused with dpi-dots per inch, which refers
to the resolution of a halftone screen), 16 bit depth, you generate
a 120 MB file. This
is probably the optimal resolution to be sure that you are getting
the best possible file. However are you
capturing 120MB worth of useful information?
Most likely not, because sampling as finely as 4000 ppi
means that the sampling is finer than the film grain.
This means that some of the samples are of the edge of
film grain, and some samples are between film grain. If you also
consider the fact that the highest quality digital capture images
are the so called RAW files, which are usually compressed by
a factor of 50%, the efficiency of digital capture goes up even
more. I have found that a 7.7 MB Nikon D1x raw file is more than
equivalent to a 120MB 35mm film scan judged as either an inkjet
print, or in offset reproduction.
Andrew
Rodney (www.digitaldog.net) has on
his web site, a discussion where he compares 18MB digital capture
files to 4x5 scanned film, and concludes that "in virtually
every aspect, the digitally captured image file thoroughly outclassed
the file scanned from filmä".
These
fine points are lost on some people in the industry (especially
offset printers) who insist that digital capture images need
to be as large as film scans to be of equal quality. Another
piece of dubious information is that a digital capture image
needs to 300 ppi at the final reproduction size in order to be
successfully printed.
The
300 ppi figure is a legacy of scanned film, which as I have mentioned
before is a less efficient means of digitizing a photo. A digital
capture needs to be only 1.5 times the line screen resolution.
Most line screens are either 133 dpi or 150 dpi. This means that
ideal resolutions for digital capture images meant for printing
would be in the neighborhood of 225 ppi.
Make Some Tests: Actual tests
have shown that there can be a degradation of image quality at
300 ppi vs. 225 ppi. Intriguingly, the default resolution for
Adobe's RAW file processor is 240 ppi.
If
your offset printer does not agree with this premise, perhaps
you can get them to run some tests for you.
In some cases, 300 ppi is preferred by the offset printer
in order to give them some head room in case the image needs
to be cropped or enlarged slightly. Another situation where 300 ppi may be preferred
would be if the printer is using a 200 line screen.
Use of 200 line screens is not always the path to higher
quality, however. "The
finer the screen ruling, the smaller the dots, but the smaller
the dots, the harder they are to print properly.
If they are on the cusp of what the press can tolerate,
the following irritating things happen: * Darker areas start
to plug up, resulting in perceived lower maximum shadow. * The
minimum acceptable highlight dot goes up; at some point, a dot
simply gets too tiny for the plate and the blanket to hold. Overall detail in the
highlight will become inconsistent. * The image will begin to
appear soft as the transition areas become less distinct. * Dot
gain will appear to increase." Dan Margulies, Professional
Photoshop 6.
There
is, however, an important feature that film has which digital
does not, and that is the ability of the photographer, client,
agency, designer, and printer to judge the intended color of
the image accurately, and without special software or equipment.
In order for digital to work across all of these levels, there
needs to be a way for everyone in the chain to view the image
in the same way. The solution to this problem is called color
management.
RGB:
First some background. Photography, whether captured on film
or digital, is originally in RGB color: Red, Green, and Blue.
This is also how our eyes see color-I'm sure we all remember
rods and cones from high school biology. A transparency on a
light table or an image on a computer monitor is an RGB image.
When computers started to be used to display photos, a system
needed to be worked out to translate RGB values into numbers,
as computers can only work with numbers. The system involves
3 channels- the Red, Green & Blue channels, and each channel
is divided into at least 256
discreet tones (or more if the file has 12, 14, or 16
bit depth)of those colors. By combining those 3 colors in various
combinations, millions of colors can be described on a computer
screen.
CMYK:
When an RGB image needs to be translated to the printed
page, we need to convert from RGB to CMYK. CMYK stands for Cyan,
Magenta, Yellow and Black. Theoretically we would only need CMY,
except for the fact that printing inks are not as pure as RGB
light is, and if you add 100% values of CMY, you get brown and
not black. The black plate is labeled K. The black plate, besides
giving us a real black, is useful for printing type, rules and
other graphic features without having to worry about CMY inks
hitting the same precise spot.
Every
RGB and CMYK device translates the same color numbers slightly
differently. Caucasian skin tone is roughly described as R 220,
Green 190, and Blue 165. In CMYK, the numbers might be Cyan 09,
Magenta 28, Yellow 33, and Black 0. However, your monitor, if
it is not profiled, will very likely display those values quite
differently from a profiled monitor. This is because all devices have different
color characteristics.
If you've ever seen a wall of T.V. sets at Circuit City
all tuned to the same channel, you'll see what I mean.
Each T.V. is displaying the same color information differently.
Monitors: Profiling a monitor means that you use a hardware calibration device with supporting software to optimize the monitor brightness and contrast, neutralize the monitor's display of color, and provide an .icc profile, which will become the default monitor profile used by color savvy applications such as Photoshop. Once profiled, the RGB numbers in a file are changed before they are sent to the video card so that your monitor displays them accurately.
Once
your monitor has been profiled, you should then check your Photoshop
color settings. The Default color settings when installed are
for Web, which assumes sRGB color space, and color management
turned off. This needs to be changed
to U.S. Prepress defaults- at least as a starting point. This changes the working color space to the
wider gamut Adobe 1998 color space, and turns color management
on. Your files if worked on
and saved in this color space will now be "tagged"
as Adobe 1998 files. What this means is that
each file will have the Adobe 1998 color space embedded as a
profile. This is important, because
in color management, it is important that any profiled device
should see that embedded color space profile in order to properly
display a file, and then to be able to accurately convert it
to any other desired color space, such as a specific CMYK space.
Although
monitor calibration and profiling is the very least that everyone
needs to do in this era of digital photo files, far too few clients,
agencies, designers and even photographers are taking this seriously.
If we also consider that many of us are using desktop
printers, we see that if they are left as they are "out
of the box", they don't even match our own screen, except
in a very general way.
Desktop Printers: The color management
solution for desktop printers is to get custom profiles for each
type of paper that you are likely to use. There are several Internet
services that do this. Visit their web page, read the instructions,
download and print out a color chart, mail it back to them, and
they will e-mail you a profile or set of profiles.
With
a little bit of effort, the application of color management will
allow your device and my device, and the graphic designer's device
across town all give us the same version of a picture.
That would be all for the good, but what happens when
we go to offset printing?
CMYK: In the CMYK arena, we have
real trouble brewing. Many offset printers are still operating
under the old paradigm: they receive color film and put it on
a drum scanner which has been carefully set up and calibrated
to their press conditions. This scanner converts RGB to CMYK
on the fly, and all the pre-press work is done in CMYK. This
is called a "closed-loop" system, and it has worked
very well for many years and continues to work well as long as
that offset printer is not having to deal with files (especially
not RGB files) generated outside of his shop. Since there is
only one scanner involved, there isn't a lot of difficulty getting
original image color to match up to their proofing printer and
presses.
The
difficulty for me as a photographer was that although the results
were often quite nice, they were never exactly as I had intended.
This is because a technician was the final judge of color and
contrast. Another difficulty with this system is that CMYK is
not the ideal set of channels to do retouching.
Retouching
and color corrections are better handled in RGB, where the picture
originates. CMYK color is a very small gamut (range of colors)
compared to RGB. It doesn't take many color moves in CMYK before
unpleasant side effects such as banding, posterization and color
clipping start to emerge. There is also the fact that CMYK files
are very device dependent, meaning that files prepared for one
offset printer, may not work as well on another company's presses. If you are going to spend
a lot of time and effort (money) retouching that special file,
it would be best to store it as an RGB "masterfile"
so that it can be repurposed to any number of CMYK spaces.
Unfortunately,
too many of today's pre-press technicians at too many printing
companies are unfamiliar with working in RGB color.
At
this point, we seem to have reached the point of maximum chaos
in trying to produce a printed piece. We have digital RGB files
being generated by photographers who fail to color manage them.
These files are too often not tagged with a known color space.
They are then handed off to clients who may not know how
to look at them accurately. They are then passed on to designers
and advertising agencies who "correct" the color without
the benefit of profiled monitors and proofing devices, and then
they end up at a printer's shop, usually still RGB, where the
printer tries to convert them from an unknown color space to
his CMYK space. This is where he complains about the "awful"
color, and "flatness" of the image, and then tries
to heroically correct the color in the worse possible space,
CMYK. When the client or designers see the proofs, they may experience
"shock" and when they get the printer's invoice they
may experience "awe".
What to do? First we need to recognize
that we are in a whole new set of circumstances. The methods
of the past will only continue to frustrate. If a person's job
description involves reviewing and evaluating photography, then
they should equip themselves with a reasonably new (fast) computer
with the latest version of Photoshop. They should also research,
install and learn to use good Digital Asset Management software
such as Extensis Portfolio, Canto Cumulus, or iView MediaPro.
It
is a very good plan to have an external Firewire or USB2 hard
drive of some reasonable size (120 Gig for instance) to serve
as a back up and quick access storage for digital files. A fast
CD burner and a set of shelves where CD's can be organized and
stored are also essential. With digital photography, CD's are
the current coin of the realm.
DVD is another possibility.
If your average job generates a half dozen CD's, then
DVD storage would probably make more sense for you.
Photoshop
out of the box has default settings that need to be changed.
Photoshop color settings are found under the Edit menu (Windows)
or Photoshop menu (Mac OSX). These settings should be changed
from Web settings (the default) to U.S. Prepress Defaults. This
ensures that your color space will be Adobe 1998, and that color
management will be turned on. A printer I visited recently had
complained that my digital files did not "look good"
on his monitor. When I asked him to go to his Photoshop settings,
he had Web defaults for his color settings. This meant that he
was assigning the wrong profile to my files, and then stripping
out the correct profile. Once a file is saved like that, the
original color can never be recovered.
Since
that time, I never take for granted that anyone knows how to
set up their copy of Photoshop, so I always take them to that
menu and check it with them. Next step is to get a monitor calibration
device and software and profile your monitor. If you have a printer,
get a profile for a glossy paper and a matte paper, so you can
see the effect of printing on coated or uncoated stock.
Advertising Agencies: According
to one survey I came across recently, some 62% of advertising
photographers are using digital capture. Hopefully, this means
that advertising agencies will become accustomed to digital files
and color management. Those that have taken
the time to train their front line people are to be applauded,
but this is not yet universal.
Case in point,
I have gotten
some of the strangest and most inappropriate photo files I have
ever encountered from ad agencies. Although Photoshop supports
almost every file type known to man, I have received files from
one agency that had to be run through a hardcore program called
"Graphic Converter" before they could be opened. Needless
to say, these files were untagged and I had to interpret the
color based on sky being blue, grass green, etc.
A
client should not accept this from any agency because it costs
them extra time and money for someone down the line to sort this
out. A file like that sent to the average printer is a recipe
for disaster. It would be prudent for the client to at least
have a discussion with their agency rep about some of these issues.
A
proactive approach might be to send a letter to the agency requesting
that people working on their account use profiled monitors, and
use only TIFF or JPEG files in appropriate sizes, resolutions
and quality. I would also recommend that Adobe 1998 color space
be used as the standard color space, and that all digital files
be tagged in that space.
Photographers:
The center of the storm. A minority is very much on top of the
digital revolution. Many others are using digital cameras without
really understanding the workflow. Some are in total denial that
film is rapidly losing ground to digital capture in the commercial
arena.
Much
progress is being made, however, and a few questions by a savvy
client or designer can separate the wheat from the chaff.
Because
of the current lack of RGB support by printers, it is my recommendation
that photographers should be chosen not only for their "eye"
but for their ability to handle color management, retouching
and prepress.
There
are service bureaus emerging that may come to replace the "color
lab" with retouching and prepress services for those photographers
unable or unwilling to do it themselves. Like I said, there is
maximum chaos at the moment.
The
good news is that almost all manufacturers' resources are going
into new digital products. New cameras with increased
resolution, full frame chips, new kinds of chips, and improved
software for decoding RAW files, are being announced every few
months. It's only going to get better for photographers, if,
and only if, they have already invested in a digital infrastructure.
Unfortunately,
getting into the digital photography business will be increasingly
difficult as the cost of admission now includes very expensive
cameras, laptops, storage media, computer workstations, printers,
etc., all of which need to be color-managed.
Offset Printers: I feel that printers
should be chosen on their ability to print. As long as the client
has good support from their designers, photographers, and agencies,
delivering good CMYK files to their printer should not be a problem.
Every
printer that I have worked with has been willing to e-mail me
his or her CMYK profile. If they don't profile their
offset press, then get their proofing printer profile, since
they are probably good at matching their own proofs on press.
I have found that the best piece of information is to
get them to send to me their Photoshop custom file settings (.cfs),
which includes the CMYK profile as well as their Photoshop settings.
This clues me in to whether they have Photoshop set up correctly
to preserve the embedded profiles.
That
being said, color management will only get you so far when it
comes to offset printing. Offset presses can only be profiled
up to a point. After that, the skill of the pressman, the paper
choice, and even the humidity level the day of the press run
become more important.
Our
goal should be to give the pressman the very best file going
in so he only needs to adjust for press conditions, and not try
to make major color shifts due to problems in the CMYK files.
Despite the rapid changes occurring in
the photography, design, and printing workflow, there exists
now a set of standards that can and should be applied.
Monitors: Monitors whether
CRT or LCD needs to be profiled with a monitor calibration device.
White points of 6500K for web and 5500K for print are good starting
points. If you have
a profiled printer and a color correct viewing booth or viewing
light reasonably close to the 5000 standard, the proper white
point can be determined by dimming the viewing booth while looking
at a copy of the plain white stock you are planning to proof
on until the brightness of the viewing booth matches the brightness
of the monitor. Then you should adjust the monitor white point
until it matches the proofing stock.
Alternatively, you can profile the monitor to several
white points from 5000 to 6500, and find the color temperature
that most closely gives you a match from monitor to profiled
printer.
Desktop
printers: Desktop printers should be profiled so that what
you see on the monitor matches what is printed on paper as closely
as possible.
Digital
Cameras: There are currently 2 types of professional grade
digital cameras. These are Digital SLR cameras, and Digital Backs
that mount onto either medium or large format cameras. Both of
these professional camera systems produce the high-resolution
wide gamut files necessary for high quality reproduction. Whichever
type of system is used, they should be set on Adobe 1998 or equivalent
color space. Whenever possible, the RAW file format should be
used for maximum quality and color correction capabilities.
Two
file types are becoming standard for photographs, TIFF and JPEG.
Other useful file types are PDF, EPS, and
TIFF
(tagged image file format) Files are the most universally recognized
industry standard image format. TIFF files can be compressed,
but it is generally preferred that they be delivered in uncompressed
form, usually on a CD. TIFF files can thus be large when not
compressed, but they are a "lossless" format meaning
they can be saved again and again without degradation. When uncompressed,
they should be only the size and resolution required to conserve
disk space and to speed up Photoshop operations.
TIFF
files can be either RGB or CMYK, and they should always be tagged
with a color space. TIFF files delivered to a printer should
be accompanied by a guide print. Remember that the printer does
not have the advantage of having a transparency for reference.
The Guide Print should come from a profiled printer, and should
be printed using the CMYK file, or from the CMYK proof color
space to mimic the offset press.
TIFF
files can be delivered via the Internet using FTP (file transfer
protocol). Files delivered his way can be zipped or stuffed depending
on the receiver's platform. These files will not have the benefit
of a guide print, however, so the state of the receiver's color
management needs to be determined.
JPEG:
The other file type that is standard is the JPEG (Joint Photographic
Experts Group) file. This format provides the most dramatic means
of file compression, which is why it is a standard Web file type.
This file compression, however, comes at a price. The higher
the level of compression, the more 'lossy' or subject to image
degradation the file becomes.
An
18 MB file can be compressed to around 1 MB with very little
loss of quality, however compressing it much more than that will
start to create jpeg artifacts. Also, opening a JPEG, making
any changes to it, and then resaving it as a JPEG will result
in file degradation. Therefore, JPEG files can be used to good
effect as long as you don't go too far with the compression,
and plan to convert them back to TIFF files before doing any
retouching or color correction.
Saving
large TIFF files as high quality JPEGs is a reasonable storage
strategy as long as these rules are respected. As with TIFF files,
JPEGs should be tagged with a color space.
PDF:
One other file format bears mentioning, and that is the PDF (Portable
Document File) file format. PDF files are excellent for showing
layouts to someone by e-mail, or for showing photos to someone
who doesn't have a copy of Photoshop on their computer. Almost
all computers sold today have a copy of Adobe Acrobat installed.
PDF files are small (easy to e-mail), and can reproduce documents
created in Quark, InDesign, Illustrator, as well as Photoshop.
A PDF sent by e-mail and printed out on a profiled printer gives
the recipient a color correct hard copy of a layout.
EPS,
Photoshop: Other file types such as EPS and PhotoshopÆ
files have good attributes as well and can be used say between
a photographer and designer, or photographer and offset printer
just as long as both parties agree to the particular file format. If you don't know where the file is going,
then TIFF or JPEG should be used.
Digital
photo files take up lots of hard drive space. Digital photography
could not take off until hard drive capacity got really large.
10 years ago, a 1 GB hard drive was almost unheard of. Now 120
GB drives are routine, and the match book size compact flash
cards used by digital cameras are available in 256 MB, 512 MB,
even 1 GB sizes. Sizes up to 6 GBs are under development.
Graphic
designers running Quark on old Power PC's will find their systems
brought to their knees trying to open the average digital camera
file. Optical storage media such as CDR and DVD are probably
the safest media for long-term storage. External hard drives
are the fastest and most convenient but not necessarily the safest. A combination of the two
methods is probably best at this time.
The
client needs to develop a strategy for storing and accessing
digital files. Is the Photographer going to do it, or is the
client going to be responsible for it? Unless specifically spelled
out in a contract, the photographer is not necessarily archiving
clients' digital files.
In
order to realize one of the major advantages of digital, namely
exact duplicate searchable files, someone needs to create, store,
and manage this resource. Probably the quickest and easiest storage
method at this time is to archive all digital files on CDR or
DVD, label the jewel case spines, and stored in some kind of
order in a specially designed shelf unit. A more flexible system
is a set of external hard drives containing a catalog to all
the digital files contained on that drive.
Digital
files contain so-called "EXIF" data, which can be used
to sort and find specific files. It is probably an excellent
idea for the client to develop a set of "file info"
standards to be used by all contributing photographers.
Digital
Asset Management: There are programs available such as
PhotoMechanic (Mac) or Digital Pro (Windows), which will insert
into every photo file a complete dossier of information. At the
very least, that information should include the date and time
of the shoot, the location and project, a description or caption
of the picture, the photographer, the copyright information,
and any other keywords or categories that can be used by a search
engine to locate a specific shot on a computer disc.
For
convenience, it might be a good idea to standardize the file
renaming protocol. Digital cameras automatically name every file,
but those file names are not particularly informative. Programs
such as PhotoMechanic or iView Media Pro allow you to rename
files in a more descriptive way- such as GlenelgSports 001.jpg-
for instance.
Once
the file information and naming parameters have been agreed to,
the resulting database practically builds itself. This can be
a huge advantage in choosing which pictures should be used for
various advertising, brochure, annual report and web projects.
Conclusion: Although
hardly exhaustive, I hope the points I have made help make the
advantages and challenges of the digital photography revolution
a little more clear. I hope that others involved in this creative
process will weigh in with information that I have missed or
failed to make understandable. I am confident that two things
are true, this revolution is here to stay, and everything will
get better and easier as time goes on.
References: Fraser,Murphy,Bunting Real World
Color Management, Blatner,Fraser Real World Photoshop
6, Martin Evening Adobe Photoshop 7 For Photographers,
Dan Margulis Professional Photoshop 6.
Web-site references:
http://www.luminous-landscape.com
http://www.robgalbraith.com\
http://www.dpreview.com
http://www.nikondigital.org
http://www.prodigital.org
http://www.juergenspecht.com/d1scussion
http://digitaldog.net
All Text © Richard Anderson
Digital Standards
and Practices Working
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