I meant that all the hdr programs work differently on a single image then they do multiples.
On singles all they generally do is bump up contrast and a bit of sharpness - extra contrast loses detail in the dark and high light areas = reduced tonal range. clipping, if you like.
Test image, from camera:
Same image, hdr'd - note less detail on leaves.
I agree that a 3 picture HDR has three time the ammount of light in it, therefor it should have a better tonal range. A single picture HDR only has the same ammount of light as a standard picture, but what do you mean by a reduced tonal value?