Hi @Ral-Film
As you can see in other posts my yart project is similar to Manuel’s, both inspired by the original Joe Herman project. https://forums.kinograph.cc/t/super-8-scanner-based-on-dominique-gallands-software/2106
So my experience with HDR is the following.
- As Manuel says you first need to have the lighting adjusted so that the exposure time for an average image is about 4ms (at ISO 100). The exposure time is limited upwards by the framerate and downwards by the sensor reading. For example if the lighting is too weak the exposure time cannot be increased enough to get the overexposed HDR image.
- I am dubious about the interest of making 6 exposures, in my opinion 3 are enough and this is especially true since it takes about 4 frames to stabilize an exposure and therefore it reduces the throughput considerably.
- In my case I do not count in stops but in ratio, my values chosen experimentally are 0.1 for the under exposed image and 2 for the over exposed image.So for example exposures 0.4-4-8 ms (This is quite consistent with Manuel’s values)
- Amateur films can have large variations in exposure, I think that the automatic exposure for obtaining the middle image is interesting, it gives a starting point. This is usually what I choose. Note that this still reduces the throughput because about 8 frames are needed to stabilize the automatic exposure.In the end with a resolution of 1920x1080 the capture requires about 2s per frame.
- The Mertens algorithm is simple and effective, I could not get satisfactory results with Debevec.
- My program has the possibility in preview or in capture to display or save the unmerged images, this is really useful to adjust the exposures.