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sRGB vs. ProPhoto

Forum|Forum|9 years ago
August 31, 2016
3 replies
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I have a question regarding color space that’s been bothering me for a while that I can’t seem to find an answer to. Basically, with regard to sRGB, AdobeRGB and ProPhoto and my editing in ACR, Lightroom, Photoshop, etc. I don’t know if it matters at all switching to ProPhoto when 95% of the monitors out there are representing the sRGB gamut and a few are the AdobeRGB?

If my base assumption is wrong, then I’m happy for someone to explain, and further help me understand how it matters to have my software set to ProPhoto and edit with a monitor that at best is AdobeRGB. Naturally, I don't use sRGB for anything but exporting, so the emphasis of the question is for editing. As a side note, I recently purchased a new 4K display, and during my research I read about the sRGB vs. AdobeRGB display space, and thusly ended up purchasing an LG that has the AdobeRGB space. I have traditionally used the ProPhoto space with Photoshop EDITING. I have since switched “down” to AdobeRGB for editing as I thought MAYBE it is better if everything is adjusted to the same space.

I also understand printing may come in to play, for that my edited photographs are either exported via jpeg online, and then printed by that host via their sRGB/jpeg, or I print a TIFF file directly from Lr or Ps.

Thanks for your time and attention.

Thomas Logan

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Correct answer D Fosse

The main advantage of ProPhoto is that it gives you headroom in the editing process. You can work without running into gamut clipping from which you can't recover. Once a channel is clipped, that information is lost.

For final output, ProPhoto makes little sense since no output device can reproduce the full gamut. You'll need to remap anyway and the remapping needed may be very extensive.

I said in another thread that the ProPhoto gamut is mainly artificial, meaning that these extremely saturated colors are rarely found in real life. There is in fact an interesting concept known as "Pointer's gamut", which represents all real-world reflected colors from a solid object, as seen by the human eye. It happens to fit rather comfortably in Adobe RGB:

http://www.tftcentral.co.uk/articles/pointers_gamut.htm

As for monitor, a wide gamut ("Adobe RGB") unit is very useful for soft proofing, because it can reproduce virtually all printable colors - inkjet or offset. This means you can soft proof with confidence. A standard unit is considerably less useful in this respect. Everything you see on screen is already soft proofed to sRGB and a lot of printable colors are outside monitor gamut.

c.pfaffenbichler

Community Expert

Another thing worth keeping in mind is that when working in a large Color Space it may be beneficial to work in 16bit to avoid quantisation effects when converting to a smaller target space.

D Fosse

Correct answer

Community Expert

The main advantage of ProPhoto is that it gives you headroom in the editing process. You can work without running into gamut clipping from which you can't recover. Once a channel is clipped, that information is lost.

For final output, ProPhoto makes little sense since no output device can reproduce the full gamut. You'll need to remap anyway and the remapping needed may be very extensive.

I said in another thread that the ProPhoto gamut is mainly artificial, meaning that these extremely saturated colors are rarely found in real life. There is in fact an interesting concept known as "Pointer's gamut", which represents all real-world reflected colors from a solid object, as seen by the human eye. It happens to fit rather comfortably in Adobe RGB:

http://www.tftcentral.co.uk/articles/pointers_gamut.htm

As for monitor, a wide gamut ("Adobe RGB") unit is very useful for soft proofing, because it can reproduce virtually all printable colors - inkjet or offset. This means you can soft proof with confidence. A standard unit is considerably less useful in this respect. Everything you see on screen is already soft proofed to sRGB and a lot of printable colors are outside monitor gamut.

alexit3748321

Inspiring

D Fosse skrev:
The main advantage of ProPhoto is that it gives you headroom in the editing process. You can work without running into gamut clipping from which you can't recover. Once a channel is clipped, that information is lost.
For final output, ProPhoto makes little sense since no output device can reproduce the full gamut. You'll need to remap anyway and the remapping needed may be very extensive.
I said in another thread that the ProPhoto gamut is mainly artificial, meaning that these extremely saturated colors are rarely found in real life. There is in fact an interesting concept known as "Pointer's gamut", which represents all real-world reflected colors from a solid object, as seen by the human eye. It happens to fit rather comfortably in Adobe RGB:
http://www.tftcentral.co.uk/articles/pointers_gamut.htm
As for monitor, a wide gamut ("Adobe RGB") unit is very useful for soft proofing, because it can reproduce virtually all printable colors - inkjet or offset. This means you can soft proof with confidence. A standard unit is considerably less useful in this respect. Everything you see on screen is already soft proofed to sRGB and a lot of printable colors are outside monitor gamut.

Well, sRGB, AdobeRGB or ProPhotoRGB are not output profiles - i.e you don't print from those profiles. So in that sense, neither of them makes much sense for output. However, going from working profile to output profile is like trying to fit a round peg in a square hole. If you want to make sure the peg fits you need to make the hole bigger. That's where ProPhoto comes in.

Printers have a very different shape to their gamuts because they are based on the reflectance of real pigments and paper, as opposed to being emissive like computer displays. This means that some colors easily falls outside the emissive gamuts, while others sit quite comfortably inside. To encompass all of the colors you can print you need a large gamut. ProPhoto is very good that way, because it's huge. With AdobeRGB you may still find some colors get clipped by the printer.

ProPhoto is not mainly artificial. It has some imaginary colors in the blues and greens. Imaginary colors are mathematical abstractions and fall outside the gamut of human vision. It's got nothing to do with rarity in real life. These color don't exist other than as abstractions - you can't see them. The primaries are quite useful when defining a color space though.

Pointer's gamut doesn't sit comfortably at all inside AdobeRGB. You might want to check your own link again. And that's with only 2D representations of the gamuts.

D Fosse

Community Expert

I take issue with incorrect information. Falsehoods do not simplify things, they complicate and lead people astray. That's not very pragmatic.

I'm not nitpicking when saying that Pointer's gamut extends beyond AdobeRGB, and it's not just a little bit.

Talking about hyper-saturated colors is hyperbole. Of course saturated colors make "colorful" prints. It's equally true that our perception of color is relative, making color relationships very important.

You don't "need" sRGB either. It just happens to work very well for it's intended purpose. Same thing with ProPhoto. It makes a very good job of encompassing every output gamut. That means, making the most out of the colors that your digital camera can capture. That way you can also make sure that you get the most out of your output media, and that the files you are working with are not stripped of valuable information.

It's not a tiny fragment of colors, and good photolabs today tend to have printers with gamuts outside AdobeRGB. As inks develop we'll see wider gamuts and more printers that support them. Here's one example of a printer gamut outside AdobeRGB:

http://www.colorwiki.com/images/e/ee/News_52.png

That's not what i'd call tiny.

Bottom line: ProPhoto is an excellent color space, assuming you're working on high bit depth images, as it allows you to keep the most amount of data and encompasses all available output color spaces.

OK. Let's look at this from the opposite angle.

How do you deal with the conversion from ProPhoto to the print profile? Do you just let the profile handle it, or do you actively remap from ProPhoto to print? Because if you are using ProPhoto unchecked, so to speak, you are likely going to get massive gamut clipping in this conversion.

Gamut clipping is rarely pretty, and has a much more severe impact on the finished image. That is my main concern in all of this. I go to great lengths to avoid it. The risk of uncontrollable gamut clipping downstream is much higher if you use ProPhoto uncritically. It's much less likely to happen if you try to contain and control gamut from the start. In any case the remapping to output will be much easier.

This is what I mean by "bigger fish to fry". I gladly sacrifice a few saturated colors If it can control gamut clipping downstream.

Another advantage, by the way, which I think should not be underestimated: With a wide gamut monitor, you can actually see everything that's going on in your file. Yes, I know you don't need to see it. It's just nice, and a bit reassuring.

Derek Cross

Community Expert

As a matter of interest those on a Mac might like to look at the ColorSync Utility (found under Utilities). There you can compare color spaces such as sRGB and Adobe RGB (you can use the curser to rotate the chart). Some might be surprised to see how small the CMYK space is.

Thomas Logan ArtAuthor

Known Participant

Thanks for that tip Derek. I'll be checking that out!

Derek Cross

Community Expert

Here's a CMYK space typical for a commercial litho printing. See how much smaller than RGB.

The space of a (say) ten-color desk-top inkjet printer would be a bit larger.

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