Assign Profile vs Converting to Profile

This relates to a very lengthy thread in the InDesign forum, ''RGB vs CMYK images and resolution''

I have a lot of questions (perhaps confusing) relating to RGB color gamuts. To simplify let's start with 2 gamuts, ProPhoto and Adobe RGB

I have a profile editor that can view both of these within potato-shaped Lab gamut. They are of course both triangles, I believe all RGB gamuts are. I can see ProPhoto is considerably larger than Adobe RGB, containing more fringe colors

I also see that the gamma of Adobe RGB is 2.2. The white point is 6500K

The gamma of ProPhoto is 1.8. The white point is 5000K

I understand gamma to be ''black point''. Or better yet ''black density''. On a press sheet, ink density can be measured with a densitometer. In my experience a density reading of 2.2 on a press sheet would be very dark. Is my understanding correct - that gamma (RGB) is comparable to ink density (CMYK)? Perhaps better to state as an analogy: Gamma: RGB as Density: CMYK

My monitor RGB profile has a gamma of 1.8 (mac standard). This tells me that the Adobe RGB gamma of 2.2 has to be re-interpreted on my display. Is that correct?

As for white point, that would be the RGB equivalent of CMYK paper white.

The InDesign forum has a lot of discussion about assigning profiles, vs converting to profiles. My understanding is that assigning a different RGB is actually a ''pure'' conversion. The pixels are left completely intact. There is no move to Lab, and back to RGB. It's taking the image and effectively dropping it into a brand new gamut, The price for this, of course, is that the appearances of the colors are completely redefined, and this appearance shift can at times be radical.

For example, if I have an ProPhoto image open, then assign Adobe RGB, I can see very clearly that the image becomes darker on-screen, and the color ''shrinks''

As a prepress person, I have often used re-assigning in RGB mode as a very effective color correction tool. Usually it's turd polishing, to be quite honest, when critical color match is not an issue. The scenario is usually a crappy sRGB image. I assign Adobe RGB, which as the Adobe description states is ideal for conversion to CMYK. I must add that I always use proof preview, I am well aware that Adobe RGB has colors far beyond a standard CMYK gamut. But when I convert to CMYK, using Adobe RGB as the source, the image color is expanded, and the result on press is often vastly improved.

I will also add that as a prepress person, I don't go re-assigning in this fashion without the customer's consent.

In the InDesign forum, this ''re-assigning'' has been referred to as ''random color''. There is a lot of emphasis on color appearance, and maintaining color appearance. The consensus therefore is that if you had an sRGB image, you should convert to Adobe RGB. But then it is my understanding that you miss out on the often huge benefit of gamut expansion. If you wanted to expand color after converting, you have to do color corrections, which alters the pixel data and in the strictest sense is destructive (unless you use adjustment layers).

All this leaves me wondering - if assigning is such a no-no, why is it available? Probably the main reason for the assign capability is to assign profiles to images that don't have an embedded profile. Sometimes users unknowingly discard profiles, if the color settings policy is set to off. When another user open the image, he quickly sees the image does not have a profile.

Normally he would assign his working space, since that is affecting his visual on-screen appearance. But he can't know for sure if that's true to the original capture.

Which brings up another point. Any device doing the capture (camera or scanner) has a gamut. This gamut is an input profile.聽 When the image is translated from device capture into digital file, should this input profile be embedded in the image?

At this point I'm not sure about this. I have a 7.1 MP camera, and the downloads always have sRGB embedded. Not a profile specific to the Kodak model. My guess is that sRGB is a universal standard, representing the gamuts of monitors and desktop scanners. It is the working space of the world wide web. So it's more or less the default RGB, and is also the default working space in all Adobe applications (North America general purpose).

But the description of sRGB is very clear. It is not ideal for prepress, this is stated in Adobe's description. It is small. This may make it comparable to CMYK, but it is still not ideal for conversion to CMYK. And in fact there are CMYK colors that fall outside of sRGB. Especially if you are dealing with the larger CMYK gamuts corresponding to new offset screening technologies (FM screening and concentric screening)

So why in the world would someone convert from sRGB, to Adobe RGB? There's no benefit at all. May as well leave it sRGB, instead of converting. And the even bigger question - how do you know that sRGB is ''true'' color? To me, the true color is the original subject. In the case of a photo, that might be just a memory. In the case of a scan. it's the original, but the user might not even have that, if someone else did the scan and all he has is the digital file. So who's to say that the embedded profile - sRGB - is a fair representation of the original?

Re-assigning RGB profiles may be an odd way of adjusting color. But it can be effective. Why would the assign option be readily available, if not to translate colors to a different gamut, without altering pixel data? Seems to me it is the primary reason Adobe developed the assign option in the first place.

I know this is a lot of questions. Any input on any of these matters would be greatly appreciated.

Assign Profile vs Converting to Profile

Try again, posting only one question per post, as concisely as you can.

Assign Profile vs Converting to Profile

I don't think your post is going to find many users here willing to read it in its entirety, and even less who will attempt to answer it.

You make an awful lot of wrong assumptions, a lot of irrelevant ones, and many unnecessary ones.

Start learning about Color Mangaement here:

http://www.gballard.net/psd/cmstheory.html

In the next post, I'll explain the difference betwen Assigning and Converting to you.

This excerpt copied and pasted from an old post of mine may help you understand the difference between CONVERT and assign.

To understand profiles, think of your image as text, and of the profile as a tag that indicates in which language the text is written.

If you see text that says GIFT, you need to know whether it's in English or in German. If in German, the word means ''poison'', if in English, it means a present.

Other examples: ONCE means ''eleven'' in Spanish but ''one time'' in English.

MOST means ''Bridge'' in Russian but ''greatest in amount, extent, or degree'' in English and ''fruit juice'' in German.

If you change the language (profile) by ASSIGNING, you change the meaning of the text (appearance of the image). The numbers representing the colors in your image will remain the same, but the colors will change because the same numbers now mean something else (as the meaning of the text will change if you now read the same letters in a different language).

CONVERTING to a profile will preserve the colors while the numbers change, in the same manner as the text will retain its meaning if you TRANSLATE it into a different language, changing the letters but preserving the meaning.

Bottom line:

ASSIGNing a different profile will preserve the numbers and will change the colors of the image;

CONVERTing to a profile will preserve the colors and change the numbers accordingly.

Printer_Rick wrote:

鈥y monitor RGB profile has a gamma of 1.8 (mac standard).

Printer_Rick wrote:

They are of course both triangles, I believe all RGB gamuts are.

Finally, you should know that there is a dedicated Color Management forum in these Adobe forums, and that's where this type of discussions belongs鈥攏ot here, really.

http://forums.adobe.com/community/design_development/color_management#

Ramon,

Sorry for the lengthy initial post. I appreciate your response. I know it is a lot of questions. I'm not sure what you mean by irrelevant assumptions.

I'm not new to color management, and I am aware of color theory. And I understand the difference between assign and convert. Assign preserves numbers, convert attempts to preserve appearance

I will restate as 3 concise questions in separate posts.

Adobe RGB聽 and Kodak Pro Photo RGB are large gamut (PRoPhoto being one of the largest) device Indepedent profiles (sRGB is too).

sRGB is a narrow gamut profile intended to try to reproduce an uncalibrated monitor and atenuate diferences from the same image shown in diferent monitors.

All CMYK are a device dependent profiles that determine a print intention.As a usefull exercice go to Edit - %26gt; Color Settings -%26gt; CMYK and choose ''Custom CMYK'' so you can see what in fact a CMYK profile is.

Being new to this forums dont know if I can do this,but I would recomend you read late Bruce Fraser book ''Real World Photoshop'' focused on Color Management or at least read some of his articles at Creativepro:

http://www.creativepro.com/articles/author/127446

Printer_Rick wrote:

Why would the assign option be readily available, if not to translate colors to a different gamut, without altering pixel data? Seems to me it is the primary reason Adobe developed the assign option in the first place.

Printer_Rick wrote:

I'm not new to color management, and I am aware of color theory.

WRONG.聽 Profiles are complex three-dimensional bodies in space.聽 You're looking at a simplified 2-dimensional projection on a single plane that tells you very little.

Printer_Rick wrote:

I will restate as 3 concise questions in separate posts.

Miguel Curto wrote:

Being new to this forums dont know if I can do this,

Miguel,

Thanks for the response I will look into it.

No, Adobe, didn't develop ASSIGN so you could wreck images willy-nilly.

Plonk!

Assign profile is there for you to assign IF the image comes with no embedded profile.Period.

EDIT:Thats the closest thing you'll find to cheats on Photoshop.Why would you want to brake something that works well?

Give a look on those articles...they are very well writen and clear.

Either that or youre writing an article about Color Management and want to demonstrate something on screen.

Finally, you should know that there is a dedicated Color Management forum in these Adobe forums, and that's where this type of discussions belongs鈥攏ot here, really.

Printer_Rick wrote:

sRGB is Adobe's default RGB color space. It is the standard for world wide web. It is used by Pantone. In short it is the RGB profile most commonly encountered

I will re-iterate it's not my working RGB space, I don't care for it, I don't consider it ideal for CMYK conversion.

Thanks for the input

When saying sRGB is the most common profile, I meant it's the one I see most. My RGB policy is set to preserve embedded. The VAST majority of images I receive from clients use this profile. My thinking is most designers do not change the default color settings (North America general purpose)

Usually when I open these sRGB images, reassign Adobe RGB, then convert to CMYK, the result is much better than sRGB - CMYK. If my RGB policy was set to Off, I would get the same effect as re-assigning - my working space is Adobe RGB.

I'll add I only throw out the embedded sRGB if the the customer requests pleasing color, and the proof preview is crud. Otherwise I have to honor the sRGB.

Printer_Rick wrote:

When saying sRGB is the most common profile, I meant it's the one I see most. My RGB policy is set to preserve embedded. The VAST majority of images I receive from clients use this profile. My thinking is most designers do not change the default color settings (North America general purpose)

Usually when I open these sRGB images, reassign Adobe RGB, then convert to CMYK, the result is much better than sRGB - CMYK. If my RGB policy was set to Off, I would get the same effect as re-assigning - my working space is Adobe RGB.

I'll add I only throw out the embedded sRGB if the the customer requests pleasing color, and the proof preview is crud. Otherwise I have to honor the sRGB.

Ram贸n G Casta帽eda wrote:

To understand profiles, think of your image as text, and of the profile as a tag that indicates in which language the text is written.

If you see text that says GIFT, you need to know whether it's in English or in German. If in German, the word means ''poison'', if in English, it means a present.

Other examples: ONCE means ''eleven'' in Spanish but ''one time'' in English.

MOST means ''Bridge'' in Russian but ''greatest in amount, extent, or degree'' in English and ''fruit juice'' in German.

If you change the language (profile) by ASSIGNING, you change the meaning of the text (appearance of the image). The numbers representing the colors in your image will remain the same, but the colors will change because the same numbers now mean something else (as the meaning of the text will change if you now read the same letters in a different language).

CONVERTING to a profile will preserve the colors while the numbers change, in the same manner as the text will retain its meaning if you TRANSLATE it into a different language, changing the letters but preserving the meaning.

Bottom line:

ASSIGNing a different profile will preserve the numbers and will change the colors of the image;

CONVERTing to a profile will preserve the colors and change the numbers accordingly.

Usually when I open these sRGB images, reassign Adobe RGB, then convert to CMYK, the result is much better than sRGB - CMYK. If my RGB policy was set to Off, I would get the same effect as re-assigning - my working space is Adobe RGB.

I'll add I only throw out the embedded sRGB if the the customer requests pleasing color, and the proof preview is crud. Otherwise I have to honor the sRGB.

Miguel Curto wrote:

To make this example I would have one patch of color (in Adobe RGB or even sRGB)and dulicate it 3 times.Then would leave original alone and CONVERT the others to Scanner,Monitor and Printer Profiles.But in Photoshop they all look alike (like this one bellow):

Was DYP wrote:

I know exactly what you are talking about, and there is no reason not to use this approach if you achieve the desired result by doing so. I have many timed re-assigned (I like this name much better than false profile) an image in Adobe RGB to some other RGB space like Ekta Space or others to achieve the desired look when converting to CMYK. It is no more of a trick than to make image adjustments for the same reasons.

My original post had valid questions. I was searching for valid answers. I was not trying to suggest how someone should set up a color management workflow.

Why have I angered you so much? That was not my intent. If you have insight, you can share it without including insults or personal attacks.

Printer_Rick wrote:

No, the opposite. I receive the sRGB. Assign Adobe RGB. Color is expanded.

Printer_Rick wrote:

It's useless, Miguel.聽 Anyone with an IQ above room temperature and a modicum of understanding of color theory can easily spot the blatant fallacies this [edited by host]聽 guy keeps coming up with, post after post.聽 I've now plonked him, so I don't even see his posts at all.

Ram贸n G Casta帽eda wrote:

It's useless, Miguel.聽 Anyone with an IQ above room temperature and a modicum of understanding of color theory can easily spot the blatant fallacies this guy keeps coming up, post after post.聽 I've now plonked him, so I don't even see his posts at all.

Miguel Curto wrote:

Actually no.Since Adobe RGB is much larger than sRGB if youre assigning sRGB values to Adobe RGB you end up''with lots of free space''.

PS- Im not hangered in any way... this is a ''healthy'' discussion...the objective of this forums I think.We dont have to agree but many people come here and they should get facts straight...

PeterK.. wrote:

You're screwing up your client's intended colour. They viewed it as sRGB, saved it with sRGB because that's the final image they settled on, and then you just arbitrarily decide to assign AdobeRGB and convert to CMYK? Let me guess... then the client complains that the colour is off and you charge them for ''edits.''

It's just a bad workflow. If the client's file is not coming out on press as it looks on screen, you need to profile your press better so that you can convert the client's RGB to your CMYK and have it match. Assigning a different profile because it suits your subjective taste is ridiculous.

(besides, skin tones often take on an ugly reddish tone by incorrectly assigning AdobeRGB to a sRGB image.)

If I send you a sRGB file, that is how I viewed it in Photoshop, how I saved it, and how I expect it to look. Even for a client that request ''pleasing'' colour, if they're sending you a sRGB the assumption is the same. They approved that image and sent it out the door like that, so for what reason are you screwing with their intended colour from the outset?

I did not post my original questions to anger anyone

Thanks for that. Maybe you can help with this question, I posted earlier in color management (at Ram贸n's suggestion):

''Should input RGB device profiles (camera, scanner) be embedded and used as a source space, for conversion to CMYK? Or converted to another RGB space (such as Adobe RGB), then converted to CMYK? I don't see where 2 conversions are beneficial, but I could be wrong...''

The main reason I ask this is, I very rarely see RGB images with scanner and camera profiles embedded. To be honest most I receive are sRGB, or don't have a profile at all.

Not being a photographer, I don't download camera images for correction in Photoshop. My scanner produces a LAB image (I work in Linocolor when scanning), so no RGB profile there either.

Printer_Rick wrote:

Thanks for that Miguel, I appreciate it. I did not post my original questions to anger anyone

I should clarify. I receive an sRGB image. I assign Adobe RGB. On-screen the color is more saturated. This saturation carries over into the subsequent CMYK conversion.

Try it with any sRGB image. Convert to CMYK, save a copy. Then assign Adobe RGB, convert to CMYK. Compare the two CMYK images, I think you'll see what I mean.

It is not a specific color correction by any stretch, but it's not random rearranging of colors either.

Miguel Curto wrote:

Youre partially right,I does look more satured,I made a mistake assuming it would be the other way around but I can see whats happening.I know why but it would be really hard for me to explain...on the other hand can I suggest you something?:

Save those both images (original sRGB and the other you assign to AdobeRGB) and save them both (as JPGs for instance).

Now open both in a non ICC aware aplication (Internet Explorer will do just fine).Can you spot the diference?

''Should input RGB device profiles (camera, scanner) be embedded and used as a source space, for conversion to CMYK? Or converted to another RGB space (such as Adobe RGB), then converted to CMYK? I don't see where 2 conversions are beneficial, but I could be wrong...''

Save those both images (original sRGB and the other you assign to AdobeRGB) and save them both (as JPGs for instance).

Now open both in a non ICC aware aplication (Internet Explorer will do just fine).Can you spot the diference?

The diference between those two images is only the tag or the labbel so to speak.ICC aware apps as Photoshop,Mac Preview or Safari (this is new to me) are ''smart'' enough to try to translate those RGB values to your monitor values.The values between those images are exactly the same...youre only changing its name to trick those apps to render the values in a diferent manner.

It may work,and toure right..its not random but it would be considered as ''exploit'' and in my view two wrongs dont make one right.

Having said that,theres a lot of things that make no sense that in the end might suit some needs.

Ramon might slam me for this but Ill give you an example:

Theoretically if you start with a 8bit/channel image theres no point in converting to 16bits for editing.But it so happens that Photoshop ''mechanics'' work better in 16bits so in the end (for extreme corrections) there is a real and mesurable gain (Wich I can post here to proove)

In that process youre throwing away some ''finess'' in color witch should be adress as editing image but nothing is writen in stone and as long you REALLY understand the implications of what youre doing theres no WRIGHT or WRONG.

Was DYP wrote:

But certainly do not save an image with any chance to passed along with device profiles embedded.

Theoretically if you start with a 8bit/channel image theres no point in converting to 16bits for editing.But it so happens that Photoshop ''mechanics'' work better in 16bits so in the end (for extreme corrections) there is a real and mesurable gain (Wich I can post here to proove)

In that process youre throwing away some ''finess'' in color witch should be adress as editing image but nothing is writen in stone and as long you REALLY understand the implications of what youre doing theres no WRIGHT or WRONG.

Only pays off on (very) extreme corrections..otherwise might as well leave it at 8bits because the results will look the same and you save time.

If you start (capture) at 16bits (most scanners and cameras do 12bits but Photoshop assumes as 16 anything more than 8bit/channel) its a diferent story...

It takes some intervention and if someone really does not know what they are doing the output could be pretty screwed up. Although now days PS is pretty smart about this situation as long as you have the right color management policies selected. But if the images is used in something else, who knows.

Only pays off on (very) extreme corrections..otherwise might as well leave it at 8bits because the results will look the same and you save time.

If you start (capture) at 16bits (most scanners and cameras do 12bits but Photoshop assumes as 16 anything more than 8bit/channel) its a diferent story...

Was DYP wrote:

It takes some intervention and if someone really does not know what they are doing the output could be pretty screwed up. Although now days PS is pretty smart about this situation as long as you have the right color management policies selected. But if the images is used in something else, who knows.

Most people have their head shoved up their butt- so anything that you do with their permission and understanding to make the image better is a valid workflow...

Printer_Rick wrote:

Sounds reasonable. Now let me ask this. You are provided a really bad sRGB image. It's my understanding you would:

- Convert to your working RGB space, and do massive color correction to correct appearance, instead of

- Assigning your working space, avoiding massive color correction (still perhaps doing considerable adjustments)

Either way, you are greatly changing the original color (which you know is terrible). But with assigning, there is no trip to Lab and back, which is (technically speaking) destructive. (Adjustments don't have to be destructive when using adjustment layers)

''And what if a moron unwittingly embedded the wrong profile in output? Then assigning a different one would restore the original color.''

I stated this in post 18, I'd like to clarify what I meant.

Let's assume a photographer gives a designer an RGB image, with Adobe RGB embedded. But the designers RGB policy is ''Off''. He opens the image (effectively discarding the profile), adds a logo or type, saves and closes.

Now the image is handed off to another designer. This designer places the image in InDesign CS3. The document space is sRGB. He outputs using PDF/X-4, no color conversion.

The image in the PDF has been re-assigned to sRGB, not converted. sRGB becomes the new source for conversion to CMYK.

The job is proofed. The photographer says, ''What happened? The color's all wrong''

In this instance, reassigning Adobe RGB to the PDF image would in fact restore original color.

You may think this scenario is not likely to happen. But these hand-offs might happen more than you think. 1st mistake is the Designer 1 throwing out the profile. 2nd mistake is designer 2 unwittingly re-assigning.

But re-assigning again is the sure way to correct the image.

Rick -

These issues happen ALL DAY LONG.聽 Some people notice and some dont. Most printers eat thousands of dollars because of Adobe Software.聽 Get used to understanding disclamers, keep your nose clean and dont care much.