I just finished reading the Fraser & Schewe book on Image Sharpening, and it causes me to reassess my understanding of Prophoto RGB. Just trying to evaluate whether my thinking on the subject makes sense within the following context:
I enjoy the challenge of making the best possible images I'm capable of producing. In some cases, I believe it would be possible to market a given print through several channels: e.g., t-shirts, posters, and fine art prints. So, it would be advantageous to create the best possible master file (e.g., a Prophoto master file), even if versions from that master file need to be constrained, e.g., sRGB version for web and CMYK version for commercial printer.
Currently, I work in Adobe RGB. I understand that Prophoto has a wider gamut than Adobe RGB, moreover, that some printers can print beyond the ARGB gamut but within the Prophoto gamut. I also understand (from an article by Jeff Schewe: Schewe Photo -sRGB VS ProPhoto RGB ) that working in Prophoto can prevent or mitigate color clipping and can, thereby, render better color gradients even for transitions between colors that are within an sRGB or ARGB gamut.
The biggest downside, as I understand it, is that there are relatively few monitors that can display 100% of the ARGB space and none that can display most of the Prophoto space. So, if I prepare an image in Prophoto, I'm "flying blind" as to those colors in the image that I can print (given the right printer) but I can't see on my display. I can use Photoshop's clipping warning to alert me that there is a problem, but that just means I need to constrain the clipped colors to a smaller gamut. If I were doing my own printing and I were able to iterate through one or more test print/color correction cycles, it might make sense. Otherwise, creating an image that includes colors that I can't see seems a bit of a crap shoot.
If I'm sending images to a commercial printer I need to soft proof my file in CMYK. If I create a website or online store, I need sRGB images. If I create a Prophoto masterfile, then convert to sRGB or CMYK, going from a very wide to a relatively narrow color space increases the likelihood that I will need to spend more time correcting color problems.
Basically, it seems that working in Prophoto may provide subtle improvements in some situations but, overall, involves a lot more downside than upside.
Well, I think ProPhoto is way overrated.
Sometimes it's necessary to "park" a raw file into ProPhoto just to handle saturated areas without premature clipping. But it's extremely rarely that you need to keep those colors. The thing is - those saturated colors are usually artifacts from the raw processing, and they usually have little relation to the actual scene or how the eye perceived that scene. More often than not, the image benefits greatly from remapping into a more realistic color space like Adobe RGB.
The major objective is to avoid gamut clipping. Simply converting a ProPhoto image to sRGB can sometimes look horrible. In keeping with the golden principle of getting everything right as early as possible in the process, it will often yield better results to try to fit the file into Adobe RGB to begin with.
More is not automatically better. A larger gamut doesn't result in "more" color - quite the opposite, it frequently results in just bad color.
The argument that some printers go beyond Adobe RGB is IMO a thin one, and I'm tempted to reply with "so what". You may be able to notice that in specially prepared test images, but in the real world the difference is negligible.