Hi Unmasked -
Sorry for the delay in responding, but we just got back from a relaxing long weekend at Chincoteague, VA, a nice beach and US National Wildlife Refuge a few hours from here.
With respect to your current problem about profile mismatch, the most important clue to the reason for this behavior is your comment: "...convert to the workingspace (monitor RGB)...".
There are two type of color profiles used by Photoshop -- one type (the "working color space") defines how colors are represented numerically within PS, and the other ("device profiles) defines how color conversions are made between how various external input-output devices (eg, monitors, printers, scanners, etc.) represent and store color, and the way colors are represented internally in PS. Unfortunately, both types of profiles are present in one big long list in PS, as if they could be used interchangeably. THEY CAN'T.
Unless one is *extremely* knowledgeable about such matters, your working color space should always be one of the standard color spaces like Adobe sRGB, Adobe RGB, ProFoto, etc. It should never (...well, almost never...) be a I/O device profile. Unfortunately, from the statement of yours that I quoted above, it appears that this is exactly what you are doing.
Hence, the reason you received the profile mismatch warning is because (from what you said) your camera is saving files and sending them to PS in Adobe RGB, but internally, PS is using your monitor profile as its color space, so, of course there will be a "profile mismatch".
As an experiment, you can check to see if my guess is correct by (a) confirming that your camera's files really are in Adobe RGB, and then, (b) changing your working color space also to Adobe RGB. If I am correct, the warnings about mismatched color spaces should stop. If I have guessed incorrectly, temporarily ignore the rest of this message and let me know what happened.
If my guess was correct, then the next thing to discuss is what color spaces (ie, both camera and PS/working) should you use in the long term. It might be Adobe RGB, but just as likely, the best choice for you might be sRGB or ProFoto.
Deciding on which is a bit complicated. On the web, you'll find considerable amounts of personal opinion on this topic. Hopefully, such opinions are based on logical factors such as experience, typical subject matter, the gamuts of your monitor and printer, etc. However, often the people who voice their opinions most strongly often either don't state these factors, or aren't even aware that they are influencing their opinions, LOL.
Here's a short version of my take on this issue.
If you want the safest and easiest approach, just use sRGB both internally within PS, and as the output color space for your camera. It's easy because you never need to remember to do color space conversions every time you are done editing a photo and you want to post something on the web or have an image printed. It's safe because if your monitor is calibrated, you'll (hopefully) never once receive a complaint about odd colors in your images by people viewing them online, colors which change depending on the browser or viewing software being used, etc.
The downside of sRGB is that some extremely saturated colors (or extremely bright, or extremely dark) won't look or print any different than nearby colors / tones that aren't so "extreme". If you have a wide gamut monitor and a good printer with many more than three ink cartridges, everything you do in sRGB will look just a bit less life-like than if you used a wider gamut working space (like Adobe RGB or ProFoto) for all your processing.
Once you move away from sRGB to any other working space, the "ease" factor immediately goes out the door. Every time you are about to post something on the web, you MUST remember to convert the image to sRGB and make a new copy of the file, labeled appropriately. If you don't do this, some people will see your image as you intended, while others with different software may see your image substantially less colorful and less contrasty than you had hoped.
Because of the above, I regard Adobe RGB as a not-very-attractive middle ground position.
Personally, if I'm shooting subjects with deeply saturated colors and a wide range of brightness, I simply go all the way to ProFoto (at 16 bpc). I have to do exactly the same type of conversions as if I had used Adobe RGB, but with ProFoto, I gain a huge amount of extra gamut. In the interest of full disclosure, I also use a very good, extremely wide gamut, regularly calibrated monitor, so it's very easy for me to see the improvement.
HTH,
Tom
PS - FWIW, if I am shooting lots of portraits under well controlled lighting conditions, since nothing is ever out of gamut, I just switch back to sRGB to save myself a bit of work.
