Other methods of color matching

Thank you Adam for getting these contributions from Charles Maurer on tweaking a photo in Photoshop and providing some timely advice on color correction. I can't wait for his third instalment.

A big part of my job is to try and take photos of quilts for promotion in our monthly newsletter. Chasing color fidelity is always a challenge but I usually get there without the assistance of color management tools. That's not to say I haven't wished for the magic bullet that this software is supposed to offer but I find it is encumbered with a terminology that is like learning a foreign language . . . and with several dialects. Charles analogy of color spaces with an amoeba is a concept I can understand!

Fortunately for me we have quilters on our staff whose eyesight and perception of color is far better than mine will ever be. So when we get a proof off our Tektronix thermal wax printer that is reasonably close to the original, I can then feel reasonably confident that our carefully selected commercial printer will come close with his CYMK inks on paper. I feel lucky that I don't have to rely on Color Management Software to obtain this result.

Charles is the first author I've encountered who is prepared to tout the sRGB color space. I'm not sure whether I'm yet prepared to change from my current use of AdobeRGB. Fabric manufacturers can now use an incredible palette of dyes so we are often chasing colors that are far more vivid and saturated than we can ever hope to see in CYMK. My phiosopphy has always been to hold on to as much resolution and color information for as long as possible whilst editing images, then if the CYMK press cannot deliver it was not because we gave away some information earlier on.

I hope we'll hear how others on this list have benefitted from the wisdom that Charles is offering.

Cheers,

John Wolff Hamilton, New Zealand Email: dtopcompwave.co.nz

I appreciated the article on color matching, but absent (or implied, but not spoken) was the program used for color printing. I assumed the author used Photoshop. If the color matching is all done correctly, does it matter which program is used, be it iPhoto or Photoshop, or are other factors than the print driver involved?

Ray Kloss

On Oct 6, 2004, at 7:55 AM, dtopcomp wrote:

> Charles is the first author I've encountered who is prepared to tout
> the sRGB color space. I'm not sure whether I'm yet prepared to change
> from my current use of AdobeRGB. Fabric manufacturers can now use an
> incredible palette of dyes so we are often chasing colors that are far
> more vivid and saturated than we can ever hope to see in CYMK. My
> phiosopphy has always been to hold on to as much resolution and color
> information for as long as possible whilst editing images, then if the
> CYMK press cannot deliver it was not because we gave away some
> information earlier on.

I had to question this as well. sRGB is very much a
lowest-common-denominator color space. It is ideally suited as a
destination profile for images that you want to ensure will display the
same on a variety of consumer displays.

In other words, it's the color-space equivalent of "web safe colors."

To use it as a source profile, let alone to edit your documents within
the sRGB color space, is probably a bad idea. What ends up happening is
you throw out all the colors outside of the sRGB "ameoba," and they're
gone forever. (And I have to echo the props for the ameoba analogy,
it's genius!)

If you're only doing graphics for web design and color accuracy is very
important to you, this is an adequate approach. If you just want it to
look good, and wouldn't mind if it looked better for some people than
for others (note that better=different) you're best off using sRGB as
your simulation profile, and keep your documents in a wider color space
(Apple RGB, Colormatch RGB and Adobe RGB are all gigantic ameobas.)

Alternately, if you want to guarantee good print output, you should
simulate an accurate (to whatever degree it's possible) printer
profile, and again, keep your documents themselves in a wide color
space.

That's the great thing about color profiling. It gives your software a
huge ability to show you what your image will output on various devices
(simulated as well as possible on your monitor -- thanks to your
monitor profile!) without having to make painful decisions to mix down
your document to a given color space. Once you're ready for output, you
can back up your maximum-fidelity file and make an output file in the
appropriate color space.

Of course, this is all rather tricky to wrap your head around. Apple's
Colorsync pages offer a very nice tutorial on the subject (and if I
remember right, TidBITS ran some articles about profiles), but even
with good explanation, it's a tricky thing to implement, particularly
if your profiles aren't up to snuff. For the point-and-shoot digicam
user, you might be better off with an sRGB-based workflow (and your
camera is probably doing sRGB conversions anyhow!), just for the
simplicity.

--Nik

On Oct 7, 2004, at 8:08 AM, Ray Kloss wrote:

> I appreciated the article on color matching, but absent (or implied,
> but not spoken) was the program used for color printing. I assumed the
> author used Photoshop. If the color matching is all done correctly,
> does it matter which program is used, be it iPhoto or Photoshop, or
> are other factors than the print driver involved?

You can use whatever you want for printing, provided that you don't
double-correct/profile your color at any stage.

Or, better yet, let me explain how all of this works.

The basic profile system works as follows:

Image --> Display --> Print

Your image has its embedded profile which is really a definition of its
color space. This has information about how big the color amoeba for
this image has to be. As per my previous post on sRGB, the larger the
amoeba, the fewer colors are going to get thoughtlessly chucked out as
you work on your image.

The you have the Display profile. This is what you get after running
your Colorsync setup (or use a photo-spectrometer) to measure the
length and breadth of your monitor's amoeba.

What happens when you get an image in "Colormatch RGB" space and your
monitor's in "Nik's Viewsonic" space? Well, that's where the color
matching system (e.g. Colorsync) jumps into action. Based on some crazy
math, it compares the ameobas together and adjusts colors as necessary
to give as true a representation of color as is possible given the
inherent differences between the two amoebas. Think of it as the common
denominator of the two.

(Side note: There are different assumptions it can make about how to do
this, which are referred to as "rendering intents." For most
pleasing-color work, you want to use Photographic or Perceptual --
they're the same thing, just different terms -- rendering. That tries
to make the picture look "good" in your system without making too many
compromises that would introduce inaccuracies.)

Then we get from Display to Print (which is a slight misnomer, since
it's actually Image --> Print). Again, it takes what the image looks
like in its color space, and then matches it (again, using the
appropriate rendering intent), and adjusts the colors as required for
the printer.

This adjustment can take place EITHER in the application, in the
printer driver, or in the printer itself (if it's a color managed
{Postscript printer). If you have it adjusted in multiple places,
you'll end up compounding the same adjustment which would create a very
very wrong looking image.

The alternative would be if you're intentionally making two color
corrections, but that's easier handled through a simulation profiles,
like so:

Image --> [Simulation -->] Screen --> [Simulation -->] Print

This would be used if you want the image on-screen to, for example,
match your printer. You'd set it up so your simulation profile for your
Display is your printer's profile:

Image --> Nik's Printer Simulation --> Nik's Viewsonic --> Nik's printer

So, it first adjusts the image to match the constraints of the printer,
then it adjusts THAT image to render as accurately possible on screen.
So, what you see is pretty close to what you get.

If you want to get even fancier, you could have your printer simulate
another printer, which can be useful for proofing purposes. (Have your
inkjet print images as though they were printed on an offset press, for
example.)

The great thing about all of this is that you can do very sophisticated
color matching and control without EVER actually changing your image!
You maintain the same high-fidelity color in the digital file, so
whatever you output it to, it will look as good as possible for that
output device. (Again, this is a good reason for using a very broad
color space, rather than restricting your whole file's color amoeba to
the gamut of your display -- something similar to sRGB.)

--Nik

On Wednesday, October 6, 2004, at 09:55 AM, dtopcomp wrote:

> Thank you Adam for getting these contributions from Charles Maurer on
> tweaking a photo in Photoshop and providing some timely advice on
> color correction. I can't wait for his third instalment.
>
> A big part of my job is to try and take photos of quilts for promotion
> in our monthly newsletter. Chasing color fidelity is always a
> challenge but I usually get there without the assistance of color
> management tools. That's not to say I haven't wished for the magic
> bullet that this software is supposed to offer but I find it is
> encumbered with a terminology that is like learning a foreign language
> . . . and with several dialects. Charles analogy of color spaces with
> an amoeba is a concept I can understand!

I agree! I worked for national magazines for many years, and realizing
the importance of calibration, I'd have a friend from the production
department come over every so often with equipment to calibrate my
monitor for me. I always knew the importance of having it done, but now
I feel I'll be able to do it myself if necessary.

>
> Fortunately for me we have quilters on our staff whose eyesight and
> perception of color is far better than mine will ever be. So when we
> get a proof off our Tektronix thermal wax printer that is reasonably
> close to the original, I can then feel reasonably confident ! that our
> carefully selected commercial printer will come close with his CYMK
> inks on paper. I feel lucky that I don't have to rely on Color
> Management Software to obtain this result.

Charles made excellent points about ambient lighting and how it affects
color perception. I haven't seen them in the MacMall or MacWarehouse
catalogs recently, but La Cie still makes a line of monitors that are
outfitted with hoods to help block out glare and mainting consistent
lighting conditions. Though I never used them, the art and production
people I worked with who did thought they were great:

http://www.lacie.com/products/product.htm?id=10037

They aren't cheap, but if color accuracy is important, you might want
look in to this or a similar product. And I'm sure there are hoods for
monitors out there.

I've got no connection to LaCie other than owning a storage drive.

>
> Charles is the first author I've encountered who is prepared to tout
> the sRGB color space. I'm not sure whether I'm yet prepared to change
> from my current use of AdobeRGB. Fabric manufacturers can now use an
> incredible palette of dyes so we are often chasing colors that are far
> more vivid and saturated than we can ever hope to see in CYMK. My
> phiosopphy has always been to hold on to as much resolution and color
> information for as long as possible whilst editing images, then if the
> CYMK press cannot deliver it was not because we gave away some
> information earlier on.

However, if you're working with imagesetting for magazines, books,
advertising, packaging, ICC color management is the industry standard -
no iffs, ands or buts. Companies that aren't happy with the output of
their products that didn't follow the appropriate profile guidelines
are highly unlikely to get makegoods. Whether or not there is a
superior method to the ICC's is irrelevant when it comes to
professional printing. sRGB is fine for photos, fabric, printing on
your home or network printer, but if you anticipate imagesetting, it's
probably too risky at this point.

Marilyn

(Apple RGB, Colormatch RGB and Adobe RGB are all gigantic ameobas.)

Actually, ColorMatch and Apple RGB are almost identical, were both developed as monitor spaces, and are of similar size to sRGB and as such are not very large. AdobeRGB can hardly be described as gigantic either, when there exist spaces like ProPhoto RGB, Wide Gamut RGB and LAB (although I don't think many people work much in LAB).

Grant Symon

On Oct 8, 2004, at 2:12 PM, Marilyn Matty wrote:

> Charles made excellent points about ambient lighting and how it
> affects color perception. I haven't seen them in the MacMall or
> MacWarehouse catalogs recently, but La Cie still makes a line of
> monitors that are outfitted with hoods to help block out glare and
> mainting consistent lighting conditions. Though I never used them, the
> art and production people I worked with who did thought they were
> great:
>
> http://www.lacie.com/products/product.htm?id=10037
>
> They aren't cheap, but if color accuracy is important, you might want
> look in to this or a similar product. And I'm sure there are hoods for
> monitors out there.

As with everything surrounding color accuracy, you can go as crazy as
you want to get that "perfect color." If you have $4,000 or so burning
a hole in your pocket, you can get yourself an "entry level" Barco
display.

http://www.barco.com/prepress/en/products/product_features.asp?
element=1816

It's better not to ask what the next level up costs.

Those LaCie monitors are quite good, but pretty much anything with a
good tube (I'm a Trinitron fan from way back) and good brightness can
be calibrated to provide solid color. If you need a hood, just paint
the monitor a neutral color (if it isn't already) and then put some
neutral or black painted cardboard on the sides to make a hood. Works
fine for LCDs, too.

For ambient lighting, just get natural light fluorescent tubes, as
suggested in the original article. Or calibrate under your usual
viewing light and you ought to compensate for it as you calibrate.
(Estimating the right light temperature is a good plan, too.)

--Nik

Anybody want to see a colour profile space?

Open ColorSync Utility and hit the Profiles button in the Toolbar.

Now select a profile from the list in the left-hand pane and you'll
see a 3D plot of the colour space.

You can tumble around in the 3D view by click-dragging, and zoom in
and out by option-click-dragging vertically.

Elsewhere it's been mentioned that spaces such as Adobe RGB (1998)
are much larger than sRGB. You can see that for yourself in ColorSync
Utility:

Display the plot for Adobe RGB (1998)
Right-click on the plot and select "Hold for comparison"
Now select the sRGB profile in the left pane

You should now be able to see how the Adobe RGB (1998) colour space
completely encompasses sRGB.

While we're in ColorSync Utility...

At 20:00 -0700 04/10/04, Charles Maurer wrote in TidBITS:
> I've set my Mac to use sRGB by default (ColorSync Utility >
>Preferences pane > Default Profiles tab > RGB Default pop-up menu).

I *think* this is only true for Panther, where Apple has rationalised
the ColorSync interface.

If I remember rightly earlier versions of OS X used a System
Preferences Pane for these settings (which was a direct descendant of
the ColorSync control panel for OS <= 9).

Andrew

I have some pointers for anyone trying to learn about colour management.

In the absence of Take Control of Color Management I would like to
recommend a book:

Real World Color Management by Bruce Fraser, Chris Murphy and Fred Bunting.
Peachpit Press.

http://www.amazon.com/exec/obidos/tg/detail/-/0321267222

It's excellently organised, clearly written, comprehensive and easy to read.

Amongst much other good stuff it includes a clear explanation of the
RGB primaries vs RGBY perceptual primaries that Charles Maurer
mentioned

http://db.tidbits.com/getbits.acgi?tbart=07840

My second recommendation is to take a look at the example ColorSync
AppleScripts that have been included as part of standard Mac OS and
OS X installations for many years.

When I was trying to get my head around colour management, I found it
extraordinarily useful to have droplets that would tell me what
profile was embedded in an image, or embed a specific profile, or
match between profiles.

They helped me understand what Photoshop was actually doing!

The example scripts are in /Library/Scripts/ColorSync

Andrew

At 07:08am on Oct 7, 2004 Ray Kloss wrote:
>I appreciated the article on color matching, but absent (or implied,
>but not spoken) was the program used for color printing. I assumed
>the author used Photoshop. If the color matching is all done
>correctly, does it matter which program is used, be it iPhoto or
>Photoshop, or are other factors than the print driver involved?

At 01:51pm Oct 7, 2004 Nik wrote:
>You can use whatever you want for printing, provided that you don't
>double-correct/profile your color at any stage.
>
>Or, better yet, let me explain how all of this works.

Nik's comprehensive answer is written from a ColorSync / Colour
Management point of view.

For those using the all sRGB approach the answer is still the same:
you can print from whatever software you choose, and what's more
you're not going to get caught out by the double-profiling problem
Nik mentions.

Let me explain too...

If you follow Charles Maurer's advice you won't be using ColorSync
when you send files to your printer. You'll be using the printer's
native drivers instead. This works for the sRGB approach because
those native drivers were designed to accept sRGB input.

At 20:00 -0700 04/10/04, TidBITS Editors (Charles Maurer) wrote:
>...you might take the sRGB approach with a $500 Olympus P-440
>dye-sublimation printer. That's what I do. If you use the P-440 from
>a Macintosh, all you do is switch it on. It needs no special set-up
>and, to my eye, its native colour management works better than any
>ColorSync profile I have found for the machine...

Since you're not using ColorSync the software you print from doesn't
even have to be ColorSync savvy (although your editing software does
have to be ColorSync aware, see later)

The neat thing about Charles' approach is that the sRGB profile is
assumed at every stage. By "assumed" I mean that you don't have to
worry about embedding the sRGB profile in your images at any stage.
(If you want to embed the sRGB profile that's fine, but you don't
have to). Even better, because only one profile is assumed throughout
the workflow you never get involved in converting from one profile to
another (a process known as "matching").

It's this single profile approach that makes an all sRGB workflow so
simple. It protects you from having to grapple with real colour
management. I believe that's what Charles meant when he wrote:

At 20:00 -0700 27/09/04, TidBITS Editors wrote:
> To this end, my next article will introduce you to the wonders
> and absurdities of colour and ColorSync. It will show you a few
> simple things that matter and describe a world of complexities
> and costs that you can ignore.

However, the all sRGB approach isn't *real* colour management (it's a
neat avoidance tactic) so be careful when you get more ambitious and
want to tweak your workflow. The moment you deviate from the single
profile all sRGB approach all this beautiful simplicity falls away.
If you want to use Adobe RGB (1998) as your workspace, or you get a
sudden urge to try out the canned profile Epson provided for use with
their super-duper-extra-lustre photo paper, you'll have to move into
the realm of real colour management. (Don't be put off. It ain't that
difficult)

I mentioned earlier that your editing software has to be ColorSync
savvy. In the all sRGB approach there is only one point were
ColorSync has to be used; it's when your editing software displays
images on your monitor by converting them from sRGB space to your
monitor profile.

Watch out for this, not all applications are properly ColorSync
aware. Older versions of GraphicConverter, for example, were not as
savvy as they might have been, and can catch you out.

There's a delicious irony in the sRGB approach. Apple have given you
an industrial strength colour management system and what have you
done? You've simulated a Windows PC, shame on you ;-)

Andrew

On Oct 11, 2004, at 3:15 PM, Grant Symon wrote:

> Actually, ColorMatch and Apple RGB are almost identical, were both
> developed as monitor spaces, and are of similar size to sRGB and as
> such are not very large. AdobeRGB can hardly be described as gigantic
> either, when there exist spaces like ProPhoto RGB, Wide Gamut RGB and
> LAB (although I don't think many people work much in LAB).

A quick trip to Colorsync Utility (per Mr. Moller's advice) verifies
this. While both are marginally larger than sRGB, they're out-amoeba'd
by Wide Gamut RGB.

Time to change my color settings!

--Nik