Stacking is crazy!

There would seem to be a benefit in color retention if you can back off on other types of noise reduction, since those algorithms often affect color accuracy. I appreciate your mentioning that those shots had some degree of NR applied. A combination of techniques seems like it would give the best overall results and I agree that a little noise is not a bad thing.

When I was involved in experiments with multiple frame processing, the benefit was increased signal-to-noise, which is what was so obvious in your previous thread. That benefit will rapidly diminish when the random noise becomes less (at lower ISO's).

It is possible to get some improvement in detail at lower ISO's by manipulating multiple frames even though, from simple analysis, it may appear that you will always be limited by the sensor resolution no matter how many shots are stacked. The reason it is possible is that, with very small camera motion between shots (unavoidable), you can actually achieve sub-pixel resolution. The improvement due to sub-pixel resolution can be calculated and it will be very slight -- as you seem to suspect. There's also the fact that camera motion can introduce some bad effects along with anything good -- should be interesting to see the results.

I spent many years doing advanced optical system analysis and I guess I'm ready to be less analytic now. I feel digital technology has advanced to the point where I'm using my large-sensor cameras less and less and living happily with the state-of-the-art in small-sensor cameras. We both agree that taking a lightweight camera with us makes photography more enjoyable.

regards,

--
Darrell