I'm experimenting with color spaces and rendering intent at the moment and did a little experiment.
I took a photo from Lightroom and opened in Photoshop as 16-bit ProPhotoRGB TIFF. A lot of the image was outside the gamut of sRGB (darker greens, oranges and yellows in particular) and therefore I expected to see some differences when I converted it to sRGB using two different rendering intents. So I created two different files from this "master" using 'Convert to Profile'; one sRGB with ACE Relative Colorimetric Conversion Intent and a second with ACE Perceptual Conversion Intent.
However, when I compare the two sRGB files in Photoshop, they are identical. I would be grateful if someone could help me shed some light on this - Why would they be identical!?
Bob - thanks for the link; I remember reading that some time in my past. However it does not answer my question. I understand (or at least thought I understood!) the difference between conversion intents, but my experiment seems to suggest it doesn't make any difference (on two separate images I've tried). I'm guessing that PShop must not be converting the way it implies it is, or the intent really does not make any difference at all (which seems less likely!).
There is no perceptual intent in standard sRGB, so there will not be any difference as you have correctly confirmed. There is an updated sRGB profile available from the icc website that has a perceptual intent in it. I have used it some time and it seems to work fine in Lightroom since you can now convert to any profile as long as it is RGB based. See here: http://www.color.org/srgbprofiles.xalter
You will obviously experience decrease in saturation when you use the perceptual version with this profile.