"Assigning" vs. "Matching" a color profile

On Tue, 29 Dec 2009 20:31:53 -0800, isw wrote:


I don't think so. But that's not the issue. I don't care whether iPhoto
(or any other specific image handling app) can display the full gamut of
the images; what I want is to not lose something that might be usable on
*future* imaging equipment, whether a better screen, or a printer, or
whatever.

Unless you have verified there are actual colors in the scan outside
of sRGB or aRGB this obseeion with colorspace is just that, an
obsession with little real implication. Given this course of reasoning
IMO you would have been much better off saving the orignal scans to 24
bit tiffs for the archival originals. Except if you have some raelyy
special images I would doubt the color info lost would come anywhere
close to the tonal graduation info lost saving to jjpeg.

In article ,
"MikeWhy" wrote:

"isw" wrote in message
]...
In article ,
me wrote:
You also
haven't mentioned what format you are saving in. A wider color space
may bring about issues given the wider space must fit into a given
amount of storage bits and hence there may be less graduations of a
given color available.

Saving as "high quality" JPEGs; these are 35mm slides, scanned at 4800
ppi on a scanner that *claimed* to be able to handle it. But there's
nothing about the JPEG encoding process that forces a restricted gamut.
Storage space is not an issue, but I need to deal with iPhoto's problem
with the scanner's profile, and I don't want to throw anything away in
the process.

Then you should archive the scans as they are, without converting the
colorspace. Your choices for JPEG are 8 bit and 16 bit. As he pointed out,
converting to a larger gamut requires more bits to maintain the same
gradation in the larger space as 8 bits in the smaller color space. A
lossless conversion will double the size of each file in the new colorspace.

Would you mind posting or emailing a small crop of a 4800 ppi scan? I have
never seen a scan that fine. Can your scanning service handle medium format
and sheet film sizes? What technology do they use?

The scanner is a consumer-grade unit from Microtek; I acquired it a few
years ago for under $200. I'm under no illusions about how good the
scanner is with regard to dark noise and so on, but I wanted at least to
start out with high spatial resolution. I have several thousand slides,
and simply couldn't afford to have them "professionally" scanned.

I've posted four screenshots from GIMP he

http://profile.imageshack.us/user/isw/

The images are in reverse order, but I couldn't figure out how to
rearrange them; I rarely post images.

The ruler at the top of the screenshots (in mm) and the info at the
bottom give some scale to the images, and to the scanner's pixel size.
The actual pixels don't begin to show up until about 400%, where 1mm is
almost the full width of the image. A bit of fringing can also be seen
at high magnifications, but I really don't know whether it is due to the
scanner, or is in the original photo (which I can't access right now).
The shot was made with a Nikon FTn using a 50mm Nikon lens and a
circular polarizing filter. In real life, that dish is 64 meters across;
it's the "deep space" antenna at NASA's Goldstone site in southern
California.

The whole file is about 1.3 MB, and I'll be happy to send it to you if
you like; just give me an address that won't mind an attachment of that
filesize.

Isaac

isw wrote:
In article ,
"MikeWhy" wrote:

"isw" wrote in message
]...
In article ,
me wrote:
You also
haven't mentioned what format you are saving in. A wider color
space may bring about issues given the wider space must fit into a
given amount of storage bits and hence there may be less
graduations of a given color available.

Saving as "high quality" JPEGs; these are 35mm slides, scanned at
4800 ppi on a scanner that *claimed* to be able to handle it. But
there's nothing about the JPEG encoding process that forces a
restricted gamut. Storage space is not an issue, but I need to deal
with iPhoto's problem with the scanner's profile, and I don't want
to throw anything away in the process.

Then you should archive the scans as they are, without converting the
colorspace. Your choices for JPEG are 8 bit and 16 bit. As he
pointed out, converting to a larger gamut requires more bits to
maintain the same gradation in the larger space as 8 bits in the
smaller color space. A lossless conversion will double the size of
each file in the new colorspace.

Would you mind posting or emailing a small crop of a 4800 ppi scan?
I have never seen a scan that fine. Can your scanning service handle
medium format and sheet film sizes? What technology do they use?

The scanner is a consumer-grade unit from Microtek; I acquired it a
few years ago for under $200. I'm under no illusions about how good
the scanner is with regard to dark noise and so on, but I wanted at
least to start out with high spatial resolution. I have several
thousand slides, and simply couldn't afford to have them
"professionally" scanned.

I've posted four screenshots from GIMP he

http://profile.imageshack.us/user/isw/

The images are in reverse order, but I couldn't figure out how to
rearrange them; I rarely post images.

The ruler at the top of the screenshots (in mm) and the info at the
bottom give some scale to the images, and to the scanner's pixel size.
The actual pixels don't begin to show up until about 400%, where 1mm
is almost the full width of the image. A bit of fringing can also be
seen at high magnifications, but I really don't know whether it is
due to the scanner, or is in the original photo (which I can't access
right now).

Thanks. That was pretty interesting. Yeah, I was curious about the fringing
also. They're likely part of the grain structure, rather than sharpening
halos from the scanner software. Those chemists in Rochester did some really
things, back in the day.

It might be instructive to look at a few slides under a microscope and
compare them with what you see from the scanner. I went through the same
exercise some years ago using an Epson flatbed. 1600 dpi was a bit of a
stretch; I settled for 2400 dpi as a workable compromise. The biggest
problems are flatness and focus. Not owning a drum scanner, I tried glass
mounts and oil briefly. Unmounting, scanning, and remounting each slide
proved even more tedious than it sounds. The lower resolution actually is
quite reasonable and usable. I have no regrets about doing it the way I did.

About the colorspace... I profiled the Epson with MonacoEZColor, and
archived the scans unmodified. I have some doubts about the precision this
chain can achieve, but it's more than adequate for my needs. I batch
converted a "working set" to sRGB, and haven't bothered to dig through the
original scans even once in all the time since.

The shot was made with a Nikon FTn using a 50mm Nikon
lens and a circular polarizing filter. In real life, that dish is 64
meters across; it's the "deep space" antenna at NASA's Goldstone site
in southern California.

The whole file is about 1.3 MB, and I'll be happy to send it to you if
you like; just give me an address that won't mind an attachment of
that filesize.

Isaac

Good luck on your project.

In article ,
me wrote:

On Tue, 29 Dec 2009 20:31:53 -0800, isw wrote:


I don't think so. But that's not the issue. I don't care whether iPhoto
(or any other specific image handling app) can display the full gamut of
the images; what I want is to not lose something that might be usable on
*future* imaging equipment, whether a better screen, or a printer, or
whatever.

Unless you have verified there are actual colors in the scan outside
of sRGB or aRGB

Do you have any doubt that Kodachrome or Ektachrome slides can have a
greater color gamut than sRGB can reproduce? Adobe 98, I'm not so sure,
but it's certainly wider than sRGB.

Isaac

On Wed, 30 Dec 2009 20:47:28 -0800, isw wrote:


Do you have any doubt that Kodachrome or Ektachrome slides can have a
greater color gamut than sRGB can reproduce? Adobe 98, I'm not so sure,
but it's certainly wider than sRGB.

You just don't get it do you. Just because the medium, digital or
analog, MAY contain a colorspace of a given size is one thing. Whether
or not it is used is another. That is why I suggested looking at your
scanned images with a color aware application which can be set to
differing working color spaces and then show out of gamut colors.

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/...88D5TII3F64BF5
to "correct" the scanner profile and then re-assgn the corrected
profile to an image?

In article ,
me wrote:

On Wed, 30 Dec 2009 20:47:28 -0800, isw wrote:


Do you have any doubt that Kodachrome or Ektachrome slides can have a
greater color gamut than sRGB can reproduce? Adobe 98, I'm not so sure,
but it's certainly wider than sRGB.

You just don't get it do you. Just because the medium, digital or
analog, MAY contain a colorspace of a given size is one thing. Whether
or not it is used is another. That is why I suggested looking at your
scanned images with a color aware application which can be set to
differing working color spaces and then show out of gamut colors.

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*.

And right now I'm trying to learn enough to understand the best way to
do that. 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). So Adobe98 is my current "best guess" as to what I should convert
these images to.

Now I need to figure out the least labor-intensive way to do that, and
why two methods, both provided by Apple, produce visibly different
results.

Isaac

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".

Isaac

On Thu, 31 Dec 2009 09:35:12 -0800, isw wrote:


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

And no one said to do so. Use a little common sense. Pick a few of the
more colorful shots and check them against aRGB. Is anything even
close to being out of gamut? If not then just go with aRGB.


And right now I'm trying to learn enough to understand the best way to
do that. 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). So Adobe98 is my current "best guess" as to what I should convert
these images to.

So then just do a couple. Compare them against the originals. Even try
subtracting one image from another to see the diff. How big is it?

Now I need to figure out the least labor-intensive way to do that, and
why two methods, both provided by Apple, produce visibly different
results.

Can't help here, since I'm a PCperson. But given decent SW this isn't
that big a deal, with scripting, batch processing, etc.

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".

If you actually looked at the link I provided, this util only makes a
given profile Colorsync "compatible", it doesn't change it elsewise.
so if this were to work you could have your cake and eat it to, no? In
the course of the time you've taken to post in this forum, you might
find the absolute best answer, with nothing to lose.