Wide gamut vs standard gamut monitor

[tzalman]

Originally Posted by Moppie

What do you base that on?

I know you can have problems with sRGB images when converting to aRGB but if your working with a file with enough data in it (e.g. 14bit RAW) there should be no difference in colour graduations.

An sRGB will always have finer color gradation than an Adobe RGB image which is in the same bit depth, but in high bit the difference is so tiny as to be negligible. Even in 8 bit the difference in minimally edited images is sub-visual. Picture sRGB as a field 50 yards long and you are allowed 256 steps from one end to the other, little baby steps of about 7 inches. Adobe RGB is a football field, but crossing it in 256 steps is also quite possible, although the steps are now more than a foot long. Still, no big problem for a normal adult. The problems can come if we do a lot of editing that causes lose of levels - the gaps become 28 inches. ProPhoto is three football fields long. Each stride has to be 42 inches, pretty much the limit of human striding. If we mess with a ProPhoto image in 8 bit it will break up almost immediately.

However make the same analogy allowing 65,000 steps in each case (16 bit). sRGB steps are 0.03 inches each one, you can't even see the feet moving, and Adobe RGB steps are 0.06 inches. The difference is there, but it's meaningless.

[Moppie]

Originally Posted by tzalman

An sRGB will always have finer color gradation than an Adobe RGB image which is in the same bit depth, but in high bit the difference is so tiny as to be negligible. ......................

Fantastic explanation.

Is this also why when I try to edit 8big JPEGs in Lightroom on an aRGB monitor they don't look right and fall apart?

[tzalman]

Compare sRGB and Adobe RGB along the magenta-green axis, where the biggest difference is.

Let's call the greenest green in sRGB G1 and the brightest green in Adobe RGB will be G2. sRGB allots 256 steps to go from magenta to G1 and Adobe RGB and your monitor use 256 steps to go from magenta to G2. That means that the monitor can use only about 200 steps for magenta to G1. When you display an sRGB image, the top 56 green levels of the 256 of which the monitor is capable are empty - your wide gamut monitor is not only using only part of its gamut, the part it is using has lower color resolution than a narrow gamut (sRGB) monitor.

As for Lightroom, when you edit a jpg LR first of all converts it to its ultra wide gamut working space and high bit depth (I suspect that LR is like PS in that it actually writes to 15 bit acurracy, not 16). However, to start off there are only 8 bits worth of real image data; 256 levels spread across 32,700 levels. For every populated level there are 128 empty levels. As you edit some of those empty levels are filled in but more of the original data levels are lost. Then the monitor display has to be reconverted back to 8 bit - probably in your video card - so it is entirely possible that you will see some image degradation.

[Moppie]

Bloody legend mate

That explains what I was seeing.

[René Damkot]

Originally Posted by Hermanssson

My question is: If I edit a photo converted from a RAW image and choose the working space sRGB - is there a risk that the colors that I see on my wide gamut differs from the colors that the people on the internet will see when I post it for viewing online?

Assuming your software is color managed: No. You'll be fine.

If you're using software that is not color managed, sRGB images will appear over saturated on your screen.

[Hermanssson]

Thanks for all the good answers guys!

I am using Photoshop CS 5 which, according to your answers above, means that I can trust Photoshop to only show the colors within sRGB if that's the selected working space? That's awesome to hear.

@tonylong: When you say "If you are using Photoshop, you can "double-check" by Soft Proofing and setting the color space to sRGB and checking for "gamut clipping"."

With soft-proofing, do you mean swapping between aRGB and sRGB with the "Convert to profile" function in Photoshop to see if any colors change? Follow up question on that - if I edit my photo in aRGB and then convert to sRGB - is the colors outside the sRGB space lost in the conversion? Or can I convert back again to Adobe RGB and regain the colors above sRGB? (I assume it's as easy as just converting and undoing repeatedly to soft-proof, but I ask anyway)

[tzalman]

if I edit my photo in aRGB and then convert to sRGB - is the colors outside the sRGB space lost in the conversion? Or can I convert back again to Adobe RGB and regain the colors above sRGB?

They are lost forever, because they have been replaced with the closest sRGB colors. But when you convert from smaller gamut to bigger gamut the computer can't just guess how to create new colors, so you remain with sRGB colors in a bigger container.

[tonylong]

Originally Posted by Hermanssson

@tonylong: When you say "If you are using Photoshop, you can "double-check" by Soft Proofing and setting the color space to sRGB and checking for "gamut clipping"."

With soft-proofing, do you mean swapping between aRGB and sRGB with the "Convert to profile" function in Photoshop to see if any colors change? Follow up question on that - if I edit my photo in aRGB and then convert to sRGB - is the colors outside the sRGB space lost in the conversion? Or can I convert back again to Adobe RGB and regain the colors above sRGB? (I assume it's as easy as just converting and undoing repeatedly to soft-proof, but I ask anyway)

If you go to View/Proof Setup and choose Custom, then in the "Device to Simulate" dropdown list you can choose a color space for your Proof Colors (Ctl/Cmd-Y). You can also in the View menu choose Gamut Warning (Ctl/Cmd-Shift-Y) which can give you a visual alert if, say, you are working in the aRGB color space, allowing for more bright/saturated colors (such as Greens/Magentas) than are in the sRGB space. Proofing in the sRGB space can show if those colors would be "subdued", and the Gamut Warning can raise a "visual flag".

Your idea of converting/undoing is something that can also show the differences, yeah.

I'd say that for most stuff you won't see much, maybe slight shifts, but if there is a question, sure! And, it can be educational to see how converting to the other profile leads to a "re-interpretation" of RGB but Assigning a profile affects CMYK values. For example, if you do a Convert to Profile, then put your mouse pointer over one colorful spot, then repeat a Ctl/Cmd-Z, you will see the RGB numbers (in the Info panel) change a bit.

Try the same thing with Assign Profile.

[Hermanssson]

Originally Posted by tonylong

If you go to View/Proof Setup and choose Custom, then in the "Device to Simulate" dropdown list you can choose a color space for your Proof Colors (Ctl/Cmd-Y). You can also in the View menu choose Gamut Warning (Ctl/Cmd-Shift-Y) which can give you a visual alert if, say, you are working in the aRGB color space, allowing for more bright/saturated colors (such as Greens/Magentas) than are in the sRGB space. Proofing in the sRGB space can show if those colors would be "subdued", and the Gamut Warning can raise a "visual flag".

Your idea of converting/undoing is something that can also show the differences, yeah.

I'd say that for most stuff you won't see much, maybe slight shifts, but if there is a question, sure! And, it can be educational to see how converting to the other profile leads to a "re-interpretation" of RGB but Assigning a profile affects CMYK values. For example, if you do a Convert to Profile, then put your mouse pointer over one colorful spot, then repeat a Ctl/Cmd-Z, you will see the RGB numbers (in the Info panel) change a bit.

Try the same thing with Assign Profile.

Thanks! I've never tried this before, but I definately will when I get home from work tonight!

[Hermanssson]

Originally Posted by tzalman

They are lost forever, because they have been replaced with the closest sRGB colors. But when you convert from smaller gamut to bigger gamut the computer can't just guess how to create new colors, so you remain with sRGB colors in a bigger container.

Yeah, that's what I expected... and it makes sense. Thanks!