I can’t provide information comparable to the in depth information of the prior posters, but I can relay my personal amateur experience. I hope it is of some help.
I’ve used multiple film exposures with limited success with my Minolta 5400 (original version). I did the blending manually in Photoshop. I did not use HDR, so I can’t comment on the HDR aspects. I always used bracketed exposures shot with a tripod.
I’ve never been able to get an acceptable alignment over the entire film frames, so I never used multiple film exposures except in limited circumstances. If, for example, I had a scene where the top portion was very bright, with a fairly well defined border between the bright top and lower darker area, I have successfully used two film exposures. In that case, I just needed to make sure that the border area between the top and bottom portions was aligned. It was not necessary that other portions of the film frames aligned.
In Photoshop I put the two scanned frames in separate layers with a layer mask and blended the mask accordingly to reveal the darker exposure of the top bright portion and the lighter exposure of the darker lower portion. If the situation is good, the technique works very well. Most of the time, however, I had alignment problems.
I’ve also used the same film frame but scanned with different scan exposures. If I did so with one scan immediately followed by the second scan, I obtained perfect (or near perfect) alignment. I then blend the two scans as described above. In this case, however, I could blend the two exposures throughout the entire film frame if necessary. In practice, however, I usually ended up with very little use of one of the two scans. I’m not sure that after all is said and done that I really accomplished much by using two scan exposures. I certainly wouldn’t guarantee that using multiple scan exposure is going to deliver results that you couldn’t obtain otherwise by normal Photoshop editing of a single well exposed film frame.
