"Assigning" vs. "Matching" a color profile

On Thu, 31 Dec 2009 09:42:28 -0800, isw wrote:


The scanner came with a profile that I have no reason to doubt, and all
the images in question were scanned using it. It's just that iPhoto gets
indigestion when trying to handle images bearing that particular profile
-- and I have no idea why, and no way to find out (the scanner maker is
no longer around). My "solution" is to move the images to a different
profile, and right now I'm trying to figure out what one would be "best".

So the simple solution as has been been proposed is to simply save the
original scanned images for future use, and convert to aRGB for your
present use. Problem solved, the future and cuurent problems need ot
be solved in a single file. I really doubt the issue with iPhoto will
be a problem in the future. Ohtherwise why not deal with Apple support
on this issue if it is indeed a valid profile?

On Mon, 28 Dec 2009 11:11:08 -0800, isw wrote:

This is on a Mac, BTW.

I have a large number of scanned slides bearing a color profile
(assigned by the scanner) that gives iPhoto fits; I'd like to change it.

Using ColorSync, I can "assign" a different profile, or I can "match" to
a different profile, but I do not understand which I should do, or (more
importantly) what the difference is between the two. Further, I don't
know which profile I should move to: "Generic RGB"; "sRGB"; or what? The
images are my own, and will not be displayed on the web. I'd like to
keep them at the highest possible "accuracy" (whatever that means).

A whole lot of googling has produced many descriptions of *how* to do
these things, but nothing on *why* or *which*.

Can anybody shed some light, please?

Isaac

I think you will find that the article at
http://www.adobe.com/digitalimag/pdf...p_colspace.pdf will help
you unravel your problem.



Eric Stevens

On Thu, 31 Dec 2009 09:42:28 -0800, isw wrote:

In article ,
me wrote:

On Mon, 28 Dec 2009 11:11:08 -0800, isw wrote:

This is on a Mac, BTW.

I have a large number of scanned slides bearing a color profile
(assigned by the scanner) that gives iPhoto fits; I'd like to change it.

Using ColorSync, I can "assign" a different profile, or I can "match" to
a different profile, but I do not understand which I should do, or (more
importantly) what the difference is between the two. Further, I don't
know which profile I should move to: "Generic RGB"; "sRGB"; or what? The
images are my own, and will not be displayed on the web. I'd like to
keep them at the highest possible "accuracy" (whatever that means).

A whole lot of googling has produced many descriptions of *how* to do
these things, but nothing on *why* or *which*.

Can anybody shed some light, please?

Have you tried using a utility such as
http://www2.chromix.com/ColorSmarts/...sion=SessID:62
A682011e0e5088D5TII3F64BF5
to "correct" the scanner profile and then re-assgn the corrected
profile to an image?

The scanner came with a profile that I have no reason to doubt, and all
the images in question were scanned using it. It's just that iPhoto gets
indigestion when trying to handle images bearing that particular profile
-- and I have no idea why, and no way to find out (the scanner maker is
no longer around). My "solution" is to move the images to a different
profile, and right now I'm trying to figure out what one would be "best".


One possibility is that, being old, your scanner uses a now
non-standard form of profile which iPhoto cannot recognise. Either
that or the files produced by your scanner have a non-standard form of
header.

How do you scan - directly with the scanner or indirectly via an
application using a Twain driver?



Eric Stevens

On Fri, 01 Jan 2010 11:00:20 +1300, Eric Stevens
wrote:


One possibility is that, being old, your scanner uses a now
non-standard form of profile which iPhoto cannot recognise. Either
that or the files produced by your scanner have a non-standard form of
header.

If you loked, I all ready pointed him to a util which might correct
such a problem.

"Have you tried using a utility such as
http://www2.chromix.com/ColorSmarts/...88D5TII3F64BF5
to "correct" the scanner profile and then re-assgn the corrected
profile to an image?"

"isw" wrote in message
]...
1) Images on Kodachrome originals *may* (depending on the subject
matter) have a wider gamut than sRGB can handle, and

You still need to consider the scanner's gamut. The hardware itself might
not be up to recording the 'Chrome's full glory; cramming it through the
scanner's profile will already have lost some of the raw information; and
each subsequent remapping will lose still more. If you really want to worry
yourself sick, the 'Chrome itself is an imperfect image of the original
scene.

I read elsewhere you were using the manufacturer's supplied profile, and I
wonder if I should even bring this up. It's better than nothing, of course,
and by itself is probably sufficient to minimize unintended color casts.
MonacoEZColor came with my Epson. It uses IT8 calibration targets, one for
transparencies and another for reflective, to build device specific
profiles. The differences between the stock profile and the custom profile
were rather significant. Switching from one to the other, there were
distinct color pops across the entire image, but none I would consider large
or damaging.

For that matter, I use X-Rite ColorChecker to profile my camera sensors.
There's nothing really wrong with the images as they come out of the camera,
but I find image fidelity improves with the custom profile. Just this
afternoon, because it's still fresh on my mind, I grabbed a quick shot of
soft sunlight caressing a bottle of Hoppe's oil sitting on the window sill.
Before applying the camera profile, the bottle was rendered almost a dull
red rather than Hoppe orange. You could almost feel the texture of the
plastic in your hands looking at it onscreen. (Printing is a whole another
exercise in anality. It's also better to not ask about the monitors and
their calibration.)

Again, there's nothing at all wrong with the images that come of the camera,
even without profiling the sensor. It's the exact same situation as your
stock scanner profile compared to a custom, measured profile. You wouldn't
normally even think about it to complain, but once you start down this road,
everything becomes a mess of profiling and obsessive white balancing and
pixel peeping. You should know upfront where this is taking you.

In article ,
Eric Stevens wrote:

On Thu, 31 Dec 2009 09:42:28 -0800, isw wrote:

In article ,
me wrote:

On Mon, 28 Dec 2009 11:11:08 -0800, isw wrote:

This is on a Mac, BTW.

I have a large number of scanned slides bearing a color profile
(assigned by the scanner) that gives iPhoto fits; I'd like to change it.

Using ColorSync, I can "assign" a different profile, or I can "match" to
a different profile, but I do not understand which I should do, or (more
importantly) what the difference is between the two. Further, I don't
know which profile I should move to: "Generic RGB"; "sRGB"; or what? The
images are my own, and will not be displayed on the web. I'd like to
keep them at the highest possible "accuracy" (whatever that means).

A whole lot of googling has produced many descriptions of *how* to do
these things, but nothing on *why* or *which*.

Can anybody shed some light, please?

Have you tried using a utility such as
http://www2.chromix.com/ColorSmarts/...session=SessID
:62
A682011e0e5088D5TII3F64BF5
to "correct" the scanner profile and then re-assgn the corrected
profile to an image?

The scanner came with a profile that I have no reason to doubt, and all
the images in question were scanned using it. It's just that iPhoto gets
indigestion when trying to handle images bearing that particular profile
-- and I have no idea why, and no way to find out (the scanner maker is
no longer around). My "solution" is to move the images to a different
profile, and right now I'm trying to figure out what one would be "best".


One possibility is that, being old, your scanner uses a now
non-standard form of profile which iPhoto cannot recognise. Either
that or the files produced by your scanner have a non-standard form of
header.

How do you scan - directly with the scanner or indirectly via an
application using a Twain driver?

Microtek never (to my knowledge) provided TWAIN drivers for the scanner
I have (on OS X). I tried VueScan, but it and the scanner didn't get
along well together. Makes me wonder if Microtek just didn't want
anybody else to talk to their stuff.

OTOH, I really have no complaints about ScanWizard (the scanner app
Microtek provided).

Isaac

In article ,
me wrote:

On Fri, 01 Jan 2010 11:00:20 +1300, Eric Stevens
wrote:


One possibility is that, being old, your scanner uses a now
non-standard form of profile which iPhoto cannot recognise. Either
that or the files produced by your scanner have a non-standard form of
header.

If you loked, I all ready pointed him to a util which might correct
such a problem.

"Have you tried using a utility such as
http://www2.chromix.com/ColorSmarts/...sion=SessID:62
A682011e0e5088D5TII3F64BF5
to "correct" the scanner profile and then re-assgn the corrected
profile to an image?"

ColorSync Utility honors the Microtek profile without complaint, as does
Preview, and Photoshop Elements, and Photoshop 7 (back when I was using
Tiger), and GIMP. ColorSync Utility's "verify" function thinks it's
fine. Both ColorSync utility and Preview are able to assign the Microtek
profile to images in the same way they will assign any other profile.

The app you pointed to doesn't look like it does anything useful in that
context.

Isaac

In article ,
me wrote:

On Thu, 31 Dec 2009 09:42:28 -0800, isw wrote:


The scanner came with a profile that I have no reason to doubt, and all
the images in question were scanned using it. It's just that iPhoto gets
indigestion when trying to handle images bearing that particular profile
-- and I have no idea why, and no way to find out (the scanner maker is
no longer around). My "solution" is to move the images to a different
profile, and right now I'm trying to figure out what one would be "best".

So the simple solution as has been been proposed is to simply save the
original scanned images for future use, and convert to aRGB for your
present use. Problem solved, the future and cuurent problems need ot
be solved in a single file. I really doubt the issue with iPhoto will
be a problem in the future. Ohtherwise why not deal with Apple support
on this issue if it is indeed a valid profile?

Now that I understand the color profile "situation" a whole lot better
than I did two weeks ago, I agree with your suggestion. the Adobe98
profile does seem to be the best choice -- sRGB would *possibly* reduce
the gamut on some of the images, and ProPhoto would necessitate a move
to 16-bit color values, something I have no intention of doing.

But it took me a while to get to this point, and some of the information
posted here was very valuable input to my decision-making process.

It is a foible of mine, that I do not feel comfortable doing a thing
merely because an "expert" (who may or may not actually qualify for that
title) says to do it. It is necessary for me to understand *why* that is
the proper thing to do.

Happy New Year to all

Isaac

In article ,
Eric Stevens wrote:

On Mon, 28 Dec 2009 11:11:08 -0800, isw wrote:

This is on a Mac, BTW.

I have a large number of scanned slides bearing a color profile
(assigned by the scanner) that gives iPhoto fits; I'd like to change it.

Using ColorSync, I can "assign" a different profile, or I can "match" to
a different profile, but I do not understand which I should do, or (more
importantly) what the difference is between the two. Further, I don't
know which profile I should move to: "Generic RGB"; "sRGB"; or what? The
images are my own, and will not be displayed on the web. I'd like to
keep them at the highest possible "accuracy" (whatever that means).

A whole lot of googling has produced many descriptions of *how* to do
these things, but nothing on *why* or *which*.

Can anybody shed some light, please?

Isaac

I think you will find that the article at
http://www.adobe.com/digitalimag/pdf...p_colspace.pdf will help
you unravel your problem.

There is indeed a good deal of useful information in there. Had I come
across it earlier in my investigation, things would have resolved
considerably faster. As it is, it reaffirms a lot of what I've learned
"the hard way", but that extra confirmation is always a good thing.

Thank you.

Isaac

isw wrote:

What I "get" is:

1) Images on Kodachrome originals *may* (depending on the subject
matter) have a wider gamut than sRGB can handle, and

2) I have no intention of measuring, one-by-one, nearly three thousand
slides, to find out which ones in fact hold images needing that wider
gamut and which do not, so

3) What makes sense to me is to handle all the images alike, and in such
a way that minimal information is lost *no matter the content*.

First: calibrate your scanner. You'll need an IT8 Kodachrome
Target (google!) for your scanner. Otherwise, you're loosing
information right away at the scanner.

Then, save the raw data from the scanner with the ICC profile from
your scanner calibration. That way, you can decide in 10 years
you want to do something different --- and you can start again
right at the point the data came into your computer. That way,
you loose no information past the scanning process.

If you want to have 'final' images (alongside the above named
RAWs!), it depends on what you want to do with them: "display
on the web" or "consumer photo developing", sRGB and JPEG is the
way to go.

So far, my understanding is that sRGB *may* cause a
(content-dependent) loss of gamut vis-a-vis Kodachrome, and that
ProPhoto can handle it easily, but is probably too large a gamut unless
I'm willing to commit to doing everything to 16 bit precision (which I'm
not).

Why not?? After all, your primary task is 'loose minimal
information', not 'stay in 8 bit and save disk space', isn't it?

So Adobe98 is my current "best guess" as to what I should convert
these images to.

Not really. The best guess is writing a small program that sees if
you loose information *for this given image* at a list of colour
spaces (sorted by size) and choose the colour space and bit depth
that looses none --- then run that over all your images and let
your computer do the work. Don't forget to attach the correct
colourspace to your images.

Now I need to figure out the least labor-intensive way to do that,

have a program do the work, see above.

and
why two methods, both provided by Apple, produce visibly different
results.

They shouldn't produce visibly different results outside
minimal adaptions for the colour space ... you might be doing
something wrong. Maybe as easy as converting to Adobe RGB, but
not attaching that information to the image, so it gets shown as
sRGB (and looks somewhat washed out).

-Wolfgang