Should I use ProPhoto RGB?

Question

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!

Answer 1

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:

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.

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[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.

Answer 2

Zeus's answer is great and comprehensive. I am just going to add some additional thoughts for some of the OPs specific questions. Some below are opinionated based on PRACTICAL REALITY and experience.

Avoid ProPhoto in Practice

I normally recommend NOT using ProPhoto. It is an ESPECIALLY bad choice for someone just starting out. And it is a particularly bad choice if your image destination is D65 (i.e. web or video) and not print (D50).

Reasons To Use ProPhoto

1. You are going to print. Especially if the print process to be used is a high quality wide-gamut process using more than CMYK (i.e. hexachrome etc). Using ProPhoto in THIS instance allows you to remain in RGB mode to do your image editing (must use 16 bit per channel or more).

Reasons to NOT use ProPhoto

2. Higher Delta E errors.
3. Wider gamut than you can display.
4. Impossible to accurately proof before print.
5. Imaginary color primaries means you could inadvertently clip relative to output and not know it.
6. Will still require transforms to another space.
7. Converting to another space adds substantial workload to the flow.
8. Requires multiple transforms to go from its D50 wp to the D65 used in web and video. More transforms means less accuracy, more losses, more problems.
9. Unpredictable results because of all the above.
10. Requires working in a higher bit depth.
11. More predictable results can be had for most print outputs by converting to the CMYK colorspace (i.e. SWOP) and soft-proofing and delivering with the print profile instead of using an arbitrarily large RGB profile and crossing your fingers it might work.
12. Provides no benefit in most scenarios.
13. In other words, it adds complexity and needless work without actually providing a real benefit in most practical applications.

It's Not The Size It's How You Use It

The main reason people say use ProPhoto is a set of misconceptions. Here are some:

ProPhoto is a bigger gamut so it has more colors.

No, incorrect. The "number" of colors is defined by the BIT DEPTH. Technically, an 8 bit per channel sRGB image has up to 16.8 million colors. ProPhoto in 8 bit ALSO has up to 16.8 million colors. But those colors are spread over a LARGER AREA, so there is more DISTANCE between them. This does not result in greater fidelity, but it does result in greater errors (visibly as "banding").

ProPhoto won't clip your image.

Yes and No, but Not Usually Relevant. Yes, it is easier to clip in a smaller gamut space like sRGB. The next larger common space is Adobe98, and if you are clipping in sRGB, then Adobe98 might be the better choice for that image. But if you are going to web, you still need to get into sRGB, so you are going to need to adjust the image to fit into the sRGB space at some point.

The best way to not clip is to use an unbounded linear floating point working space.

Your Image Won't Lose Anything in ProPhoto

No, incorrect. You always have the potential to "lose" image data and fidelity. How much you lose depends on things like bit depth and how transforms to other spaces will be performed. When you use ProPhoto, you will have to make transforms to an output space, introducing errors for instance.

As mentioned above, using a space where the primaries are farther apart means that the available bits have more distance between values so each color is less accurately represented.

Also, since ProPhoto is a D50 whitepoint, you have to use the ICC PCS to convert to sRGB and a bradford chromatic adaptation. Going through the PCS can twist colors, clip, and cause other unpredictable results.

The better way to "not lose anything" is use SmartImage when opening RAW.

ProPhoto is better for HDR imagery

Again not true, it's more about bit depth. If you have very HDR imagery, bit depth and data type are important concerns. And again, the bigger the gamut, the MORE BITS you need to describe color values therein.

Side bar on bit depth

Not all 16 bit data containers are equal. There is integer, and there is float, and there is Photoshop.

Photoshop first, as it's a special case. PS 16 bit is actually 15 bit. That's still 35 trillion color values for RGB, but only 32768 "evenly spaced" levels per channel instead of 65536. This is enough for ProPhoto when gamma encoded, but not really for HDR imagery.

Other editors use all 16 bits, but Photoshop throws one bit away if you open those images in PS. Regular integer 16 bit is 65536 "evenly spaced" values per color. When I say evenly spaced, I mean in terms of numbers not gamma encoding. Integers are whole numbers 1,2,3,4 and no "fractions", i.e. decimals like 1.253

Another kind of 16 bit is 16 bit float. This is a floating point format, and DOES allow decimal values like 1.24345 the important different is this: in integer, each number is a whole number, and there nothing possible in between those whole numbers. With a float format, there is a LOT in between those whole number values, so you can "vary the distance" between color values in a more practical way than with integer math.

Floating point math allows working in LINEAR mode as opposed to a gamma encoded mode. This is actually more useful to prevent clipping and working with HDR than the colorspace.

Note that Photoshop is not so great for linear mode, but AfterEffects IS great for linear mode.

Pros use ProPhoto, so it must be best

No, Incorrect. Pros rarely use ProPhoto except for specific circumstances that may warrant it. This is especially true with current ADoughBee products that allow "Smart Images" when opening RAW, which is more ideal way to "not lose anything" than using ProPhoto.

Other Things

Setting Working Space OP's question on working space: You can set the working space in PS under colors, and you could set it to ProPhoto so you don't get that warning, but hopefully all here have sold you on the idea of NOT using ProPhoto for your application.

sRGB is the Standard for the Web sRGB is the standard colorspace for the worldwide web. Even if you don't tag your images, browsers will assume they are sRGB. CSS4 is going to introduce other colorspaces to the web (IMO that's a bad idea but whatever) but even then sRGB will be the DEFAULT.

The implication is that you need to end up as sRGB for EVERYTHING. And sRGB is FINE as a working space if it is not clipping your images.

Linear Space I work in Hollywood as an editor, VFX Supervisor, and Title Designer. We do most of our work in a LINEAR workspace, not a gamma encoded one. Photoshop does most things (8 and 16 bit) in a gamma encoded space, whcih is also how images are saved in jpeg, PNG, and TIFF etc.

Linear means NO gamma curve (curve power of 1.0). Linear requires floating point math (we use 32 bit float). The advantage of linear is that the math works the way light works in the real world. SO the math is simpler and also "more real".

Linear is virtually "unbounded" in that you can have colors much brighter than what would be maximum white in an integer image, and you can even have negative colors as are in some colorspaces (imaginary colors). this means that you essentially CAN'T clip.

Working in a linear floating point space is actually the IDEAL solution. Unfortunately Photoshop is kinda bad at it. Try Gimp if its interface doesnt drive you mad.

Adobe AfterEffects (AE) is surprisingly better than PS for linear (being driven by the film industry) but sadly Photoshop is stuck in its legacy ways. While AE is made for film/video, when I want to work on a still image in linear, I do it in AfterEffects.

Answer 3

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.

Answer 4

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:

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.

Answer 5

I know this is an old question but I found these answers to be entirely unsatisfactory and potentially misleading, particularly involving a very important point: ProPhoto RGB in 16bpc mode as an intermediate format used for highly iterative color/contrast/tone/blending processing (and as "master final copy" afterward).

In those cases, you definitely want to be using >=16bpc to minimize mathematical losses along the way anyway, in which case you might as well also use a wider gamut, especially for raw photos.

Then as a very last step, convert to sRGB then 8bpc for final display output (assuming screen not print).

Yes it's true that ProPhoto RGB is overkill for final display on most monitors, and often just introduces colorspace headaches. (At least for now. That will likely change eventually, but by then we'll probably all be using some other HDR colorspace anyway and with better color management built into OSes and web browsers.)

And yes it's true that ProPhoto RGB is completely unsuitable for 8 bit-per-color. (You need 16 at minimum.)

But if you are doing a significant amount of said iterative work on a photo, depending on the photo, limiting to standard sRGB may repeatedly push colors past ranges sRGB can encode, only to [try to] pull them back again in later steps, with color information now lost.

In my experience of analyzing my own photos, my raw photos regularly capture colors outside the sRGB colorspace. While processing in ProPhoto RGB doesn't guarantee those colors will be visible in the final output (e.g. final conversion to sRGB), it does improve the odds, and in my experience, the end results after highly iterative editing of certain photos, are quite noticeably better. (I do alot of iterative script-based processing.)

If the image is destined to be displayed on a monitor, you should definitely consider converting to standard 8bpc sRGB as a final step. Most image processors, including Photoshop, do a good job of this. I believe Photoshop even dithers colors outside the sRGB space during conversion, and at minimum definitely does approximation magic, to provide a better result than just clipping.

I've used 16bpc ProPhoto RGB as an intermediate for quite a while now. It seems like well over 10 years, though I believe ProPhoto RGB wasn't introduced in 2011. And either way, I've been using it even when Photoshop had limited support for 16bpc, adjusting my workflow accordingly. The only time I don't use it, is when I'm processing low-contrast images with fairly constrained colors--or when gradients are more important than color fidelity--and I want to maximize the smoothness of gradients. In that case, sRGB has smaller steps (being a smaller colorspace at the same bit depth), and is theoretically less likely to produce banding. In practice, I can't tell the difference (as far as banding goes), assuming 16bpc. But in those cases it probably doesn't hurt, and I at least try to pick the optimal color space for the source material and desired result. (Mostly just between ProPhoto RGB and sRGB. Adobe RGB is too close to sRGB to bother with, for my tastes, but that's just personal preference.)

Answer 6

Especially... No. ProPhoto uses more RGB which makes some phone wallpapers dangerous. In short, ProPhoto is dangerous for phones, not PCs. Use another like Adobe RGB.