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I am fairly new to photography, and I have heard many people say that I should import my images in Photoshop using ProPhoto RGB as color space (only for the RAW images).

However, when I import my photos using 16-bit ProPhoto RGB, Photoshop tells me that "The document... has an embedded color profile that does not match the current RGB working space".

It gives me three options: to use the color space I wanted, to convert the color profile to sRGB (as my monitor, I guess) and lastly to not use a color profile and thus not handling color at all...

I have tried before to check the "keep using ProPhoto RGB" box, however when I exported my picture as JPEG and watch it on my phone, or also when trying to post it on Instagram, the colors suddenly became unsaturated and ugly, very different from the colors I saw on my PC screen.

Also, another question that I have is: if my monitor can only display sRGB color space, why would I use ProPhoto RGB? If my idea is NOT to print a photo, but mainly web usage, is it really necessary to retain colors that my screen cannot display? Also, if my monitor cannot display those colors, how do I know that I am not "messing them up" (what if for example I mistakenly change the luminance or hue of some colors that I cannot see because they cannot be displayed? How would I even know that I did a mistake?).

I hope my question is clear, although it probably isn't, as my noobish nature makes me not really understanding color spaces at all...

Thank you for your patience!

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Let me first say that everything that's happening is exactly how it should be. Even the fact that Photoshop gives you a warning, which is a matter of its Color Settings (see below). And your concerns are absolutely valid.

In a TL;DR fashion, I'll say this: only use a non-sRGB profile if:

  • You have a colour-calibrated monitor (and, in fact, the whole workflow);
  • You have a wide-gamut monitor;
  • You are prepared for the inconvenience of handling the correct colour-managed workflow (both mentally and practically).

Otherwise, stay with sRGB. Even if you do observe colour management (which is always good), it will make your life much easier, especially for your intended purpose (i.e. web/sharing photos with others).

Now the rationale.

It is true that the RAW photos of any decent camera can store more colours than what fits in sRGB (and what most monitors can display). It may feel that it would be a waste to clip them. Sure it is. But what can you do? Your output device (and that of 99% of people) is fundamentally incapable of displaying them. If you think that at least those 1% (or your printing lab) will see them, ask yourself: how are you going to process your RAWs into JPEGs and ensure that the colours that you don't see are good? [1]

If you are worried about preserving the data for posterity, you should keep your RAW originals and the XMP files (or whatever files your RAW processing software writes) that record your processing settings. If you buy a wide-gamut monitor later and want to enhance your photos, you can then load your mostly-processed RAW again, switch to AdobeRGB (or something even wider) and enhance them further.

Handling correct colour management is another skill or, I should say, a mindset. Always remember that it is only as good as its weakest link. If you do apply it, you must apply it at every stage, from display settings/calibration to photo processing to photo viewing, otherwise it all loses sense. This latter, viewing, is often the weakest link: the processing environment is at least in your hands, but viewing is in the hands of the people you share your photos with. Given that the same 99% are oblivious to colour management, you can safely assume that the colour profile you carefully attached to your photo will be ignored in most cases. This is exactly why your ProPhoto images look so washed out for other people.[2]

I like this analogy: using colour management is like specifying and handling physical units to measurements. Engineers (unlike typical IT people) know their importance and how to handle them. They know that numbers by themselves are simply meaningless. But once you know (or declare) that "3" is actually "3 metres", you can work with it. You can convert it to feet, scale it, etc., all with full knowledge of what's happening. But if you lose the unit at any stage of the process, you no longer know what it is, and all is in vain.

Same with colours: Red=3 in sRGB is physically a very different thing to Red=3 in ProPhoto. The colour profile attached to the photo specifies these units. Ignore it at your peril. Yet your users will likely ignore it. This sadly applies even to many printing labs.

So, not only you should measure your monitor (ideally with a colorimeter), but you need to ensure that:

  • Your operating system records this measurement (in the ICC or another profile);
  • Your processing and viewing software uses this profile (some software ignore the OS profile and rely on their own custom settings);
  • The software processes conversions correctly (has a good management engine). Converting colour profiles is much less trivial than converting metres to feet, and even requires user input (so called rendering intent).
  • The actual colour profile is attached to every photo you produce.

What if a photo doesn't have an attached profile? For an engineer, not specifying units is a crime, unless the default unit is strictly stipulated. Unfortunately, for missing colour profiles there are two equally common assumptions: 1) assume sRGB (preferred; all professional software have a settings which profile to use in this case); 2) ignore colour management, i.e. directly map the photo gamut to the monitor gamut. However, given that most monitors (excluding laptops) are not too far from sRGB, the results are similar for most people.

Given the sad fact that most people will ignore the profile and fall back to one of the above scenarios, your workflow should include an additional annoying step if you decide to use a non-sRGB workspace:

  • Prior to sharing the photo with anyone (and, in most cases, for printing it in a lab), convert it to sRGB and share that converted one.

I have a wide-gamut monitor and use AdobeRGB as the working colour space. But I'm also an engineer as you could guess and I naturally keep all these things in mind without trouble. Yet for many people, adherence to strict non-sRGB colour management is difficult enough to poison their lives (more mentally difficult rather than actually difficult). Yet again, if you don't do it strictly, you'd better don't do it at all. Missing one step will simply produce unpredictable result, quite possibly worse than if you didn't do anything special.

By the way, those Photoshop colour settings... To have a clear mental picture of what's happening, you should tell Photoshop to alert you of any profile mismatch:

Photoshop important color settings

And if you have a non-sRGB image or monitor, you don't have an option to ignore mistmatches and colour management in general. It would be like pasting an imperial piece to a metric drawing and pretending that it's OK to consider "3 inches" as "3 mm".

As for ProPhoto specifically... This is a very wide all-encompassing profile which is alsmost guaranteed to be wider than both the monitor and the camera. But apart from the same problem of editing it on a standard-gamut equipment where you don't see all these extra bits, you have a new one: it's so wide that the 8-bit resolution is not sufficient for it. (You are stretching the same 256 steps over a much greater breadth of the gamut, and even untrained eyes can see these steps). So you need to move to 16 bit. But as we know, JPEG doesn't support 16 bit, so you'll be limited to more exotic or lossless formats.


[1] This is not impossible: histogram is your frend. But editing "by numbers" is a special skill, and you still need to "calibrate yourself" on a real device.

[2] In the most typical situation, photos made for a wider gamut will always look desaturated and flat on normal (sRGB) displays. The reverse (oversaturation) happens if you have a wide-gamut monitor and view other people's sRGB photos while ignoring colour management.

  • Good answer overall but note that a camera RAW file can certainly capture a pure 500nm, emerald green from a laser or through a narrow filter. However, it is also well outside ProPhoto RGB and so will be clipped and desaturated when rendered in ProPhoto RGB. – doug Dec 20 '18 at 2:55
  • Surely it will capture; the question is: will it distinguish it from the closest ProPhoto green? Only then can we say that it matters. That said, some cameras capture near-infrared. There are always special cases. That's why I said "almost" :) – Zeus Dec 20 '18 at 3:23
  • It could easily distinguish such a color but only if it could render it in a larger colorspace than ProPhoto RGB. Even if a camera had "perfect" CFAs that met Luther/Ives it can't distinguish the color from one on the ProPhoto RGB limits absent converting to a colorspace larger than ProPhoto RGB. Even though such a camera would be able to capture the entire visible gamut. It's the target colorspace that limits the rendered image. ProPhoto RGB remains an excellent choice because reflected colors from real life objects are almost always inside ProPhoto RGB. – doug Dec 20 '18 at 3:31
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It depends on your intended purpose. If your output will be on typical screens (monitors, phones etc) then sRGB is going to get you the best most consistent colour accuracy. ProPhoto RGB has a wider colour gamut and so is technically better but you would only see the benefits if you are outputting to a medium that uses that colour range such as high quality print. You monitor won't even display that colour range and so you won't accurately be able to check colours.

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I have an Epson printer / and print paper combination that gets very close to Pro-Photo RGB color gamut so for this printers workflow I use Pro-Photo. So the answer is that if you have a reason as I do to use this colorspace then ProPhoto is the best tool for that workflow.

Here's an example: sRGB and Epson S900 printer gamut comparison

To the assumption below that "no printer can print all colors in sRGB" while this may be true it has no bearing on why a color space profile is chosen for any specific workflow. The real reason to chose ProPhoto over sRGB or Adobe 1998 is simply gamut volume. If the gamut volume of the printer is larger than the container space, Gamut mapping cannot happen. So the container space must be larger than the destination space.

For this printer, ProPhoto is the only color space profile that will contain the full gamut volume.

If the workflow is meant for commercial print then sRGB is too small because cyan colors are clipped in this gamut and the print space is larger.

  • The colorspace printers have is quite different than RGB colorspaces. However, all printable colors can be contained in ProPhoto RGB which is why it's best for printing. But ProPhoto RGB also has a lot of "colors" that not only can't be printed, many are imaginary colors. For that matter, as small as the sRGB colorspace is, no printer can print all colors in sRGB. Printer colorspaces and RGB colorspaces have radically different shapes. – doug Dec 20 '18 at 2:47
  • That would be correct except for the whole process of ICC profile transforms. You see that's where the math comes in to transform one gamut to another. So if you use ProPhoto colorspace and have printer close to SRGB the transform is huge and inaccurate. Much better to choose the correct and closest container space for your destination workflow. – R Hall Dec 20 '18 at 13:51
  • There is, unfortunately, a widely held, and commonly stated, view in many articles on the net, that printed image colors depend on the gamut the image is encoded in. This is not the case outside of highly specialized processes like device link ICC profiles. These are not used by photographic printing from an RGB space. A printable color in ProPhoto RGB will print exactly the same as the same in sRGB. This is because a color in an RGB space is first converted colorimetrically to the ICC PCS. From there it's converted to the printer's space. That conversion has no idea what the RGB space was. – doug Dec 20 '18 at 15:43
  • Doug, If the color is "Printable" it will be inside the gamut of the printer. As the plot above clearly shows there are colors in the gamut of the printer that are not available in sRGB, so your statement may be true for a subset of colors but impossible in the case shown above. The rest of the world does use ICC profiles to characterize printing devices and yes they do provide excellent results, but not all results for each profile gamut volume The RGB space is known in any ICC conversion because the values are mapped to CIELab. – R Hall Dec 20 '18 at 15:57
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    Then we are in agreement. BTW, I don't know why you were down voted. I agree one should use the largest RGB space that encompasses the colors in any given image. But one should be careful with ProPhoto RGB. It has the most unprintable colors of any colorspace and so editing an such an image should be done with care. My initial response was just pointing this out. That ProPhoto RGB has a huge number of unprintable colors. But it also is a colorspace that will include all colors that most good printers can print. It needs to be used if one desires a print that has those colors. So I'm upvoting. – doug Dec 20 '18 at 19:11

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