Colour management workflow for web

Apparently your camera only claims to use sRGB, but really uses Adobe RGB.

Keep doing what you’re doing – your workflow is spot on.

Maris

Derek Fountain wrote:

Another one of those colour management questions… :o}

My digital camera uses (or at least claims to use) sRGB colour space. In the past I’ve used sRGB as my working profile, and since I’ve only really wanted to put my images on the web, that all seemed satisfactory. sRGB for everything and ignore the complications!
However, I’ve just taken a set of photos in the Australian Outback where red rock is the predominant background feature. By chance I assigned Adobe RGB 1998 colourspace to the image and, wow!, the red colours just came to life.

First question, then: why, when the camera uses sRGB, does a different colour profile make the images look not only better, but more like the real world when I took the shot? I understand the idea of Adobe RGB 1998 having more colours but I don’t see why the image should be improved by using a different colour space. The camera uses sRGB, so surely sRGB is the natural colour space for the image? Why does applying a colour space which the camera knows nothing about make the image look more like what the camera really saw?

Anyhow, after this revelation, I started playing with colour management some more. My images are destined for the web, so ultimately sRGB is where I need to end up. Tweaking the image as required, then assigning sRGB back again just puts the colours back to their rather drab old selves. I tried converting the image to sRGB colour space and that seems to have the effect I want: the image is in sRGB colour space and looks right – bright colours as seen in Adobe RGB 1998 – and should look right on the average monitor.
Second question, then: Is this workflow about right: Start with sRGB, assign Adobe RGB 1998, work on the image, convert to sRGB, save for web? I think I understand the steps, but since I discovered all this somewhat by chance having an expert clarify what’s going on would help somewhat.

Derek Fountain wrote:

First question, then: why, when the camera uses sRGB, does a different colour profile make the images look not only better, but more like the real world when I took the shot?

Well, your camera claims to come close to the sRGB color space but that doesn’t mean that it always captures the reality to your liking. Some camera’s tend to over-saturate the reality and others tend to under-saturate.

I understand the idea of Adobe RGB 1998 having more colours but I don’t see why the image should be improved by using a different colour space. The camera uses sRGB, so surely sRGB is the natural colour space for the image? Why does applying a colour space which the camera knows nothing about make the image look more like what the camera really saw?

All you know is that the camera sees something close to sRGB. If you open an image from the camera in Photoshop, in the sRGB color space, you should see what the camera saw. If this is dull colors compared to what you mean they should be, then your camera captures under-saturated colors and that’s quite normal. Your job is now to correct those colors to your liking.

Let’s say that your camera has captured a reddish color with the following numbers: R:186, G:57, B:17 in sRGB.
When you assign Adobe RGB in Photoshop, you’re not changing the numbers. They will still be R:186, G:57, B:17 but those numbers will now give you a more saturated red in Adobe RGB than in sRGB because Adobe RGB has a larger gamut than sRGB. That’s why you’ll see a saturation boost when you assign Adobe RGB to an sRGB image.

Tweaking the image as required, then assigning sRGB back again just puts the colours back to their rather drab old selves.

Yes because the numbers are still the same. Assign means "keep the numbers and change the appearance according to the assigned color space"

I tried converting the image to sRGB colour space and that seems to have the effect I want: the image is in sRGB colour space and looks right – bright colours as seen in Adobe RGB 1998 – and should look right on the average monitor.

Yep and that happens because you have now changed the numbers. Still with the red color as an example (R:186, G:57, B:17) : You assign Adobe RGB to your sRGB image. The numbers doesn’t change but you’ll see a saturation boost (appearance change). It shows that the color numbers doesn’t say anything whatsoever about the appearance before we assign a color space to them.

Then you convert back to sRGB. When you’re doing that, you’re telling Photoshop: "keep the appearance (from source space to destination) and change the numbers (if necessary) in order to keep the appearance". Now the red R:186, G:57, B:17 changes to something like: R:215, G:54, B:4.
The RGB numbers has changed but the appearance (the Lab-value from Photoshop’s point of view) hasn’t.

Second question, then: Is this workflow about right: Start with sRGB, assign Adobe RGB 1998, work on the image, convert to sRGB, save for web?

If it works then I guess it’s right but as I see it, you could just as well boost the saturation in your sRGB image instead of assigning a different color space, but if it’s easier for you to assign a different color space in order to get the colors where you wan’t them to be, then why not?

—
Regards
Madsen

From: Derek Fountain

My digital camera uses (or at least claims to use) sRGB colour space.

Technically the camera has it’s own native color space (the range of colors it can capture) and it’s surely wider than sRGB. What happens is this native device-specific gamut gets mapped into one of the device-independent spaces like sRGB or AdobeRGB when the camera converts the file to this space.

In the past I’ve used sRGB as my working profile, and since I’ve only really wanted to put my images on the web, that all seemed satisfactory. sRGB for everything and ignore the complications!

That should work fine if the web is your final target, or if you’re aiming for prints from the popular Frontier-class machines, since the extra gamut is wasted on these.

However, I’ve just taken a set of photos in the Australian Outback where red rock is the predominant background feature. By chance I assigned Adobe RGB 1998 colourspace to the image and, wow!, the red colours just came to life.

AdobeRGB has a wider gamut, especially in the reds … you can see this if you make a blank layer with white background on a new document with AdobeRGB as the working space and fill several blocks with RGB = 220/0/0 – 240/0/0 in increments of 5 (ie, R = 225, 230, 240) … these should show as different shades of red (unless your monitor sux). Now convert this to sRGB and all of these will clip to R = 255 and of course look the same tone.

First question, then: why, when the camera uses sRGB, does a different colour profile make the images look not only better, but more like the real world when I took the shot?

The camera only used sRGB because you told it to, its actual color gamut is probably even slightly wider than AdobeRGB. Converting to a wider gamut simply shows more gradations of color and for reds it makes a big difference.

The camera uses sRGB, so surely sRGB is the natural
colour space for the image?

Not at all, the "natural color space" of the camera is actually different from any of these abstract, grey-balanced working spaces.

Why does applying a colour space which the camera knows nothing about make the image look more like what the camera really saw?

Because the range of colors (gamut) the camera can capture was wider than sRGB, so you didn’t have to clip colors to make it fit the space. See my example above with the red blocks.

Anyhow, after this revelation, I started playing with colour management some more. My images are destined for the web, so ultimately sRGB is where I need to end up. Tweaking the image as required, then assigning sRGB back again just puts the colours back to their rather drab old selves.

Because of this I don’t think there’s much point in going to AdobeRGB first, unless you are printing on a top flight inkjet or a laser printer like the LightJet, where the extra colors will show. You end up clipping them anyway when you convert back to sRGB.

I tried
converting the image to sRGB colour space and that seems to have the effect I want: the image is in sRGB colour space and looks right – bright colours as seen in Adobe RGB 1998 – and should look right on the average monitor.

You may still be surprised at how dull bright reds look on the "average monitor", especially on the web where there’s no color management. To preview this do View > Proof Setup > Monitor RGB.

Second question, then: Is this workflow about right: Start with sRGB, assign Adobe RGB 1998, work on the image, convert to sRGB, save for web?

I would skip the AdobeRGB step if you’re going to the web anyway, unless you intend to print on one of the printers I mentioned. On my photos with lots of reds I like to preview with the color management off to see what it will look like in a non-color managed app like the web and add a layer set to adjust for it there.

I think I understand the steps, but since I discovered all this somewhat by chance having an expert clarify what’s going on would help somewhat.

I would highly recommend the book "Real World Color Management" by Fraser, Murphy and Bunting, for a well-written in-depth look at color management.

Bill

Bill Hilton wrote:

Because of this I don’t think there’s much point in going to AdobeRGB first, unless you are printing on a top flight inkjet or a laser printer like the LightJet, where the extra colors will show. You end up clipping them anyway when you convert back to sRGB.

That’s true if Derek’s camera has captured very high numbers (like R = 225, 230, 240 from your example), but who says that his camera has done that, or am I wrong here? He wrote that the red rock keeps the appearance when he converts back to sRGB so as I see it, there’s no gamut clipping taking place in this particular case. If a gamut clipping was taking place, shouldn’t the dull colors come back, when he converts back to sRGB?

All he’s doing by assigning Adobe RGB and converting back to sRGB is to make a more saturated image because most of the numbers will be raised.

You may still be surprised at how dull bright reds look on the "average monitor", especially on the web where there’s no color management. To preview this do View > Proof Setup > Monitor RGB.

That will show him how uncompensated colors looks like on _his_ monitor and not on the average monitor. sRGB tries to simulate the average monitor doesn’t it?

—
Regards
Madsen

Bill Hilton wrote:

You may still be surprised at how dull bright reds look on the "average monitor", especially on the web where there’s no color management. To preview this do View > Proof Setup > Monitor RGB.

From: "Thomas G. Madsen"

That will show him how uncompensated colors looks like on _his_ monitor and not on the average monitor. sRGB tries to simulate the average monitor doesn’t it?

sRGB’s gamut was defined to encompass the average gamut of uncalibrated monitors, yes. But typically you strip out the sRGB profile when you save the jpeg for the web. If you don’t strip it out most browsers will simply ignore it anyway.

The main reason to check with View > Proof Setup > Monitor RGB is that very few browsers use color management. Doing the Monitor RGB check basically ignores your monitor ICM profile, showing you what the image would look like on your monitor without color management, which is closer to what someone else will see (since they won’t be viewing it with the sRGB profile or thru their monitor ICM file (if they even had one)).

If you have saturated colors, especially reds or oranges, in an AdobeRGB file you will see a big color shift when you do the ‘monitor RGB’ trick. If you convert to sRGB and do it you’ll see less of a shift but with many colors you still will see it. On a lot of my red rock photos I need to add an adjustment layer to the non-color managed file before converting to jpeg to get the colors even close to the original.

So the main purpose of the Proof Setup > Monitor RGB step is to show you what you lose without the monitor profile. sRGB isn’t an exact match for the non-color managed image’s colors and you may need to tweak them.

I don’t think there’s much point in going to
AdobeRGB first, unless you are printing on a top flight inkjet or a laser printer like the LightJet, where the extra colors will show. You end up clipping them anyway when you convert back to sRGB.

That’s true if Derek’s camera has captured very high numbers (like R = 225, 230, 240 from your example), but who says that his camera has done that, or am I wrong here?

You’re right, if he isn’t going to clip then he should go ahead and do his conversion. But he could get the same thing by shooting sRGB and increasing saturation, probably.

He wrote that
the red rock keeps the appearance when he converts back to sRGB so as I see it, there’s no gamut clipping taking place in this particular case.

I didn’t realize he had shot the red rocks in both modes, I thought he just shot them in ARGB.

If a gamut clipping was taking place, shouldn’t the dull colors come back, when he converts back to sRGB?

No, it won’t be "dull" it will just lose all the subtle tonalities between shades of colors, like in the example I gave.

Bill

Bill Hilton wrote:

sRGB’s gamut was defined to encompass the average gamut of uncalibrated monitors, yes. But typically you strip out the sRGB profile when you save the jpeg for the web. If you don’t strip it out most browsers will simply ignore it anyway.

I know but still I thought that sRGB was the color space that came closest to the common non-calibrated monitor out there.

The main reason to check with View > Proof Setup > Monitor RGB is that very few browsers use color management. Doing the Monitor RGB check basically ignores your monitor ICM profile, showing you what the image would look like on your monitor without color management, which is closer to what someone else will see (since they won’t be viewing it with the sRGB profile or thru their monitor ICM file (if they even had one)).

I often use View > Proof Setup > Monitor RGB too but only in situations where I would like to know how an image in Photoshop looks like in my browser or in Dreamweaver for instance (which both are non-color managed) but I still converts to sRGB before sending it out on the web. I seldom embed the sRGB profile because I know that most browsers ignore it but I convert to sRGB in the hope that most non-calibrated monitors out there are closest to that particular color space.

From page 291 of Real World Color Management:

Quote:
| If your work is exclusively for the Internet, calibrate your | monitor to sRGB – most monitor calibrators offer sRGB as a | preset, and for those that don’t, use 6500 K as the white | point and 2.2 for gamma. Then, do everything in sRGB. Your | calibrated color in the color-managed applications will | closely match your uncalibrated color in the non-color-managed | ones.

My work isn’t exclusively for the Internet so it happens that I prefer this workflow instead because at least it gives me consistent colors between my color-managed and non-color-managed apps.:

Quote:
| Use Monitor RGB as the source profile for all your Internet | work. Color-managed applications will see that you RGB is | already Monitor RGB, so they’ll just send the values in the | file to the screen, the same way non-color-managed
| applications do. Then, when the work is complete, convert it | to sRGB.

Mostly I prefer working in Adobe RGB though even if the work is for the web. With the soft proof function I can alway check how it would look in my browser (by soft proofing to Monitor RGB) or on the common monitor (by soft proofing to sRGB).

If you have saturated colors, especially reds or oranges, in an AdobeRGB file you will see a big color shift when you do the ‘monitor RGB’ trick. If you convert to sRGB and do it you’ll see less of a shift but with many colors you still will see it.

I see a huge difference between sRGB and Monitor RGB too and, to tell the truth, often a bigger difference than between Adobe RGB and Monitor RGB. I have always thought that the reason for this is, that the gamut of my (calibrated) monitor is closer to Adobe RGB than to sRGB but maybe I’m wrong.

So the main purpose of the Proof Setup > Monitor RGB step is to show you what you lose without the monitor profile. sRGB isn’t an exact match for the non-color managed image’s colors and you may need to tweak them.

In my case I need to tweak them a lot if I want to see the same colors in an sRGB image in Photoshop and in my browser. Here’s an example:
<http://home18.inet.tele.dk/madsen/photoshop/color/srgb.jpg>.

You’re right, if he isn’t going to clip then he should go ahead and do his conversion. But he could get the same thing by shooting sRGB and increasing saturation, probably.

I agree.

I didn’t realize he had shot the red rocks in both modes, I thought he just shot them in ARGB.

What is ARGB?
As I understand it, he has shot the red rock in sRGB because that what his camera tells Photoshop that the color space of the image is, but that’s not giving him the appearance he wants in Photoshop. He then assigns Adobe RGB and it gives him the right appearance. Then he converts back to sRGB and the image keeps the appearance which from my point of view must mean, that the camera hasn’t captured very high color numbers like R:230 in sRGB. If that was the case, it would be impossible to keep the appearance when he converts back to sRGB from Adobe RGB because of the gamut clipping that will take place from R:230 in Adobe RGB to sRGB. The red you have on R:230 in Adobe RGB (L:57, a:84, b:72) doesn’t exist in the sRGB color space. (It will change to something like L:54, a:81, b:70).

If a gamut clipping was taking place, shouldn’t the dull colors come back, when he converts back to sRGB?

No, it won’t be "dull" it will just lose all the subtle tonalities between shades of colors, like in the example I gave.

Maybe I’ve completely misunderstood Derek’s post then but if you have a very saturated red in Adobe RGB of say R:230, you’ll see a saturation drop when you convert to sRGB and that’s what I mean with the word "dull". If there’s no change in appearance from Adobe RGB to sRGB it must mean that there’s no gamut clipping taking place.

—
Regards
Madsen

Maybe I’ve completely misunderstood Derek’s post then but if you have a very saturated red in Adobe RGB of say R:230, you’ll see a saturation drop when you convert to sRGB and that’s what I mean with the word "dull". If there’s no change in appearance from Adobe RGB to sRGB it must mean that there’s no gamut clipping taking place.

I’ve been following the thread doggedly, but I think I ought to be reading the recommended book before I throw in any opinions of my own. To clarify what I’m seeing, though:

The camera is a little Canon which doesn’t offer switchable colour spaces. The EXIF data attached to each JPEG from it says it’s sRGB.

I opened a couple a "red rock" images and assigned Adobe RGB to them and the reds looks much closer to what I remember shooting. However, since my original post, I’ve noticed that other colours don’t look as accurate with Adobe RGB. Light blues in particular – I have a light blue car, and the car colour looks about right in images with sRGB assigned to them, but much too "rich" in the same images with Adobe RGB assigned to them. From this I infer that Thomas’s original assertion was correct: the camera isn’t capturing reds quite as well as I’d like and that boosting red saturation would be a better way of adjusting the images.

My understanding now is that for some colours (specifically reds) Adobe RGB matches the camera’s native colour space better than sRGB and therefore makes the image look better. For some colours (specifically light blues) sRGB matches the camera’s native colour space. On balance, and having looked at a lot of images, I can say that the majority of colours look better viewed in sRGB space.

The final step I was using was to convert back to sRGB for web output. The image colours stayed the same – there was no clipping. The reds still looked like the bright reds shown in Adobe RGB, which were accurate with regard to what I saw. After the conversion I can’t honestly claim to see any loss of subtle tonalities as Bill suggests, but then I suspect my untrained eyes aren’t as sensitive to such things. Fact is, I can’t see any difference between the original image with sRGB, and the image assigned Adobe RGB then viewed with View > Proof Setup > Monitor RGB.

I do have one more question though: when previewing with View > Proof Setup

Monitor RGB, does this take into account the fact I’m running Adobe

Gamma? That is, does it show the image as it would appear on my monitor without colour management, or does it show the image as it would appear on my monitor without colour management and without Adobe Gamma running?

Derek Fountain wrote:

Maybe I’ve completely misunderstood Derek’s post then but if you have a very saturated red in Adobe RGB of say R:230, you’ll see a saturation drop when you convert to sRGB and that’s what I mean with the word "dull". If there’s no change in appearance from Adobe RGB to sRGB it must mean that there’s no gamut clipping taking place.

I’ve been following the thread doggedly, but I think I ought to be reading the recommended book before I throw in any opinions of my own. To clarify what I’m seeing, though:

The camera is a little Canon which doesn’t offer switchable colour spaces. The EXIF data attached to each JPEG from it says it’s sRGB.
I opened a couple a "red rock" images and assigned Adobe RGB to them and the reds looks much closer to what I remember shooting. However, since my original post, I’ve noticed that other colours don’t look as accurate with Adobe RGB. Light blues in particular – I have a light blue car, and the car colour looks about right in images with sRGB assigned to them, but much too "rich" in the same images with Adobe RGB assigned to them. From this I infer that Thomas’s original assertion was correct: the camera isn’t capturing reds quite as well as I’d like and that boosting red saturation would be a better way of adjusting the images.

Sounds correct to me, particularly the part about boosting reds selectively with color correction tools. Adobe RGB "reaches out" further into the red, green, and blue corners of the gamut than sRGB does, with red and green being more pronounced than blue.

See this yourself with the Color Gamut Plotter image from Curvemeister: http://www.curvemeister.com/downloads/index.htm .

There’s a tutorial that describes how to use it. I would add that you may use the info palette, and sample points on the image to get a more quantitative read on where the corners of the gamut are, or where a particular color is on the plotter.

My understanding now is that for some colours (specifically reds) Adobe RGB matches the camera’s native colour space better than sRGB and therefore makes the image look better. For some colours (specifically light blues) sRGB matches the camera’s native colour space. On balance, and having looked at a lot of images, I can say that the majority of colours look better viewed in sRGB space.

sRGB is a good approximation for most digital cameras – which stands to reason, since the images are generally viewed on uncorrected monitors, and printed on sRGB printers.

The final step I was using was to convert back to sRGB for web output. The image colours stayed the same – there was no clipping. The reds still looked like the bright reds shown in Adobe RGB, which were accurate with regard to what I saw. After the conversion I can’t honestly claim to see any loss of subtle tonalities as Bill suggests, but then I suspect my untrained eyes aren’t as sensitive to such things. Fact is, I can’t see any difference between the original image with sRGB, and the image assigned Adobe RGB then viewed with View > Proof Setup > Monitor RGB.

You can verify this by looking at the Color Gamut Plotter with two soft proofs, one for sRGB, and another for Monitor RGB. These should be very close because sRGB is a generic monitor profile, and most monitors are not much different from sRGB.

I do have one more question though: when previewing with View > Proof Setup

Monitor RGB, does this take into account the fact I’m running Adobe

Gamma? That is, does it show the image as it would appear on my monitor without colour management, or does it show the image as it would appear on my monitor without colour management and without Adobe Gamma running?

A combination of the two. It shows how your image would look viewed on your current monitor settings, as set by Adobe Gamma, on a non-color managed application such as Netscape or Explorer.

BTW – you may want to play with the engine settings as well. I find the gamut expands ever so slightly – a few percent – when switching to the Microsoft ICM. But again, after satisfying your curiosity about profiles, hit up curves and other color correction tools. The best book for this: Dan Margulis’s Professional Photoshop.
—

Mike Russell
www.curvemeister.com
www.geigy.2y.net

Derek Fountain wrote:

The camera is a little Canon which doesn’t offer switchable colour spaces. The EXIF data attached to each JPEG from it says it’s sRGB.

Yes. I agree with Bill on the point that the camera technically has it’s own color space and that it’s probably wider than sRGB in some areas, but the camera tags the image so that Photoshop sees it as an sRGB image. It’s up to you if you want to treat it as such or not.

I have a light blue car, and the car colour looks about right in images with sRGB assigned to them, but much too "rich" in the same images with Adobe RGB assigned to them.

Adobe RGB also goes farther into the blues than sRGB (particular the light ones towards cyan), so it’s normal that you’ll see a change in the blues too. If you have a WRML-viewer(*) installed, you can see a comparison between sRGB and Adobe RGB here: < http://users.skynet.be/bk244311/gamut/assets/srgb_2_1998.wrl>. (Adobe RGB is the white wireframe).
Main page is: <http://users.skynet.be/bk244311/gamut/gamut.htm>.

(*) <http://www.parallelgraphics.com/products/cortona/> for instance.

My understanding now is that for some colours (specifically reds) Adobe RGB matches the camera’s native colour space better than sRGB and therefore makes the image look better.

If you look at a comparison like this:
<http://users.skynet.be/bk244311/gamut/assets/d30srgb.wrl> – you’ll see that the native gamut of a Canon D30 in some areas are larger than sRGB and in some areas smaller.
Your camera’s native color space probably doesn’t look like the D30’s but the gamut plot should show how different the native color space can be from the color space that the camera tags the image with. If you set the D30 to sRGB (if that’s possible but I guess it is) it can happen, that a very saturated yellow from the real world will be clipped because the native color space of the D30 can "see" deeper into the yellow areas than the sRGB color space can honour. The same thing goes with the blues and greens.

For some colours (specifically light blues) sRGB matches the camera’s native colour space. On balance, and having looked at a lot of images, I can say that the majority of colours look better viewed in sRGB space.

It must then mean that overall, the native color space of you camera is closer to sRGB than to Adobe RGB but in some parts (like the reds) it’s closer to Adobe RGB.
Since it’s overall closer to sRGB than to Adobe RGB, it would probably be easier for you to adjust the few colors you aren’t satisfied with (again the reds) in sRGB than to assign Adobe RGB and convert back to sRGB. Both sRGB and Adobe RGB are good working spaces because they’re both gray balanced and perceptually uniform. Adobe RGB is just larger than sRGB.

The final step I was using was to convert back to sRGB for web output. The image colours stayed the same – there was no clipping. The reds still looked like the bright reds shown in Adobe RGB, which were accurate with regard to what I saw.

And this is why I mean, that your camera has originally captured a red color of say R:150. If the image is tagged with sRGB, a color-managed program like Photoshop knows exactly what that color looks like (L:43, a:67, b:58).

Then you assign Adobe RGB.
The red still has the number R:150 but R:150 in Adobe RGB is more saturated than R:150 in sRGB (L:50, a:76, b:65).

You convert back to sRGB and now Photoshop changes the number to keep the appearance from source (Adobe RGB) to destination (sRGB). You now have R:233 but no clipping has taken place because both Adobe RGB and sRGB can contain L:50, a:76, b:65.

Fact is, I can’t see any difference between the original image with sRGB, and the image assigned Adobe RGB then viewed with View > Proof Setup > Monitor RGB.

I guess it depends on the quality of the monitor and the quality of the calibration and profiling but I often see a difference between sRGB, Adobe RGB and Monitor RGB because in some areas they’re very different.

when previewing with View > Proof Setup> Monitor RGB, does this take > into account the fact I’m running Adobe Gamma?

Remember that most programs doesn’t use the profile you load into Adobe Gamma. Only color-managed programs like Photoshop use it.

That is, does it show the image as it would appear on my monitor without colour management, or does it show the image as it would appear on my monitor without colour management and without Adobe Gamma running?

It shows you how your image would appear in a non-color-managed program (like Internet Explorer on the Windows platform for instance). It takes the monitor profile (the one you have loaded in Adobe Gamma) out of the loop and sends the numbers directly to the monitor because that’s what non-color-managed programs do. Normally Photoshop uses the monitor profile to correct the numbers that are send to the monitor but when you turn View > Proof Setup > Monitor RGB on, that function gets turned off.

—
Regards
Madsen

Thomas G. Madsen wrote:

And this is why I mean, that your camera has originally captured a red color of say R:150. If the image is tagged with sRGB, a color-managed program like Photoshop knows exactly what that color looks like (L:43, a:67, b:58).

I made a mistake.
I wrote R:150 but my examples was based on R:200. I’m sorry.

R:150 in sRGB has the Lab-value: L:31, a:54, b:46
In Adobe RGB it’s: L:37, a:61, b:53.

If you have an sRGB image with a color value of R:150, you’ll end up with R:176 if you assign Adobe RGB and converts back to sRGB.

—
Regards
Madsen

Bill Hilton wrote:

Bill Hilton wrote:

You may still be surprised at how dull bright reds look on the "average monitor", especially on the web where there’s no color management. To preview this do View > Proof Setup > Monitor RGB.

From: "Thomas G. Madsen"

That will show him how uncompensated colors looks like on _his_ monitor and not on the average monitor. sRGB tries to simulate the average monitor doesn’t it?

sRGB’s gamut was defined to encompass the average gamut of uncalibrated monitors, yes. But typically you strip out the sRGB profile when you save the jpeg for the web. If you don’t strip it out most browsers will simply ignore it anyway.

The main reason to check with View > Proof Setup > Monitor RGB is that very few browsers use color management. Doing the Monitor RGB check basically ignores your monitor ICM profile, showing you what the image would look like on your monitor without color management, which is closer to what someone else will see (since they won’t be viewing it with the sRGB profile or thru their monitor ICM file (if they even had one)).

If you have saturated colors, especially reds or oranges, in an AdobeRGB file you will see a big color shift when you do the ‘monitor RGB’ trick. If you convert to sRGB and do it you’ll see less of a shift but with many colors you still will see it. On a lot of my red rock photos I need to add an adjustment layer to the non-color managed file before converting to jpeg to get the colors even close to the original.

So the main purpose of the Proof Setup > Monitor RGB step is to show you what you lose without the monitor profile. sRGB isn’t an exact match for the non-color managed image’s colors and you may need to tweak them.

I don’t think there’s much point in going to
AdobeRGB first, unless you are printing on a top flight inkjet or a laser printer like the LightJet, where the extra colors will show. You end up clipping them anyway when you convert back to sRGB.

That’s true if Derek’s camera has captured very high numbers (like R = 225, 230, 240 from your example), but who says that his camera has done that, or am I wrong here?

You’re right, if he isn’t going to clip then he should go ahead and do his conversion. But he could get the same thing by shooting sRGB and increasing saturation, probably.

He wrote that
the red rock keeps the appearance when he converts back to sRGB so as I see it, there’s no gamut clipping taking place in this particular case.

I didn’t realize he had shot the red rocks in both modes, I thought he just shot them in ARGB.

If a gamut clipping was taking place, shouldn’t the dull colors come back, when he converts back to sRGB?

No, it won’t be "dull" it will just lose all the subtle tonalities between shades of colors, like in the example I gave.

Bill

What is the way to convert a psd file for non-web display on a PC, like using IrfanView or similar? Will Proof Setup>Monitor RGB also be a reasonable approximation?