I have no doubt that saving my files in ProPhoto will hold most of the RAW data instead of saving in sRGB.
Terminology: The phrase "the RAW data" is inappropriate. How about "color data" or "captured colors"?
My issue is when I do that and put this file online to print that the place I decide to print won't be able to print the ProPhoto file. Such is the case on Flickr's website. I tried clicking on the ProPhoto file to print it on Flickr and the site stated it couldn't be done. This is the problem I am running into and why I asked the original question. I do understand the file is best saved as a ProPhoto, but what good is it if I can't have the file printed with an online service? Perhaps many other online printing services are able to handle the PrPhoto file that I changed to a JPEG, but in Flickr's case, they do not allow it.
A lot of misunderstanding there. As some have already said, we use ProPhoto when editing because of it's wide color gamut. Yes, we can 'save as' a big fat 16bit ProPhoto TIFF if we must (personally I don't, for my own reasons). But there comes a time when, inevitably, your ProPhoto image
must be converted to suit the final required output, whether that is for the web or for printing. That conversion is best done by
you to your satisfaction, not by somebody elses' browser and not by some printing outfit running their standard conversion whether it suits your image or not. In other words, the image will have to be converted and
you should do it - not some unknown processor.
Case in point: I shoot a stunning yellow flower in full sunlight; I open the pre-Merrill X3F in ACR 5.4. It looks
horrible with the saturated parts looking "smeared". The reason: the captured yellows are way out-of-gamut for sRGB which is what ACR's review image color space is.
I open the same X3F in SPP 3.5.2, set to ProPhoto working space. The review image looks much, much better. After adjustment, I 'save as' sRGB to post on-line. But, sadly, the save image goes back to only slightly better than ACR's, with a lot of blues clipped to zero.
What to do?
This is the moment when we have to start reading about "rendering intent" which I will not go into here but there are ways to convert a highly saturated image so that the image retains a more natural look. In particular, google "perceptual rendering intent".
Which brings us back to ICC profiles; simple display profiles (the ones that use matrix conversion) will
not give perceptual rendering intent on your screen even if you so select it. (I do have one that does, if anyone's interested).
Note that I am not recommending perceptual rendering intent for all images: what you get from your editor as default is good enough for many.
Color management . . . don't leave home without it
Ted