EXR Confusion not fully resolved

Started Jan 25, 2014 | Discussions thread
Kim Letkeman
Kim Letkeman Forum Pro • Posts: 33,428
Re: EXR Confusion not fully resolved

alexisgreat wrote:

Kim, I think most of my posts in that other thread got lost amid the confusion- basically what I found is that in S Priority, I could shoot M size DR 400 AUTO ISO 3200 and choose 1/4,000 sec shutter speeds in very bright mid day conditions and the camera chose ISO 100. If the EXIF information is correct, this cant be because of Hardware based EXR. Since then, I've tested other shutter speed combos and I've found a way both of us can be right

So there are obvious differences between L size DR 400 and M size DR 400 at more normally used shutter speeds (M size DR 400 maintains more detail in the shadows by about 1/3 EV.) It's only at 1/>1,000 sec shutter speeds that we run into the issue of how is the camera giving us 2 stops of highlight protection when we've run out of shutter speed?

So given that EXR hardware works properly with M size DR 400 at shutter speeds of 1/1,000 sec and slower, my new working theory is that only at shutter speeds faster than this does hardware based highlight protection fail, since there is no possible way for it to work at M size DR 400 ISO 100 1/4,000 sec shutter speeds. The two ways it might be failing is that 1) it bins pixels instead so you get EXR SN even though the camera is set for M size DR 400 and 2) it actually does take two exposures and combine them but both exposures are exactly the same- both 1/4,000 sec shutter speed. I dont think even software based highlight protection works at these extreme shutter speeds, so these images would effectively be DR 100, despite what the EXIF says. I dont think the shutter speed or the ISO are wrong, because in manual mode (where you cant use AUTO ISO) I went as far as you can go with M size DR 400, and the exposures were still 2 stops overexposed compared to my S Priority settings. I'd need a 2 stop ND filter to be able to get a similar exposure in Manual mode that I was getting in S Priority.

I believe Photoreddi was able to replicate my findings, but it would be wonderful if you could take a look at this too- please set your camera(s) to S priority M size DR 400 AUTO ISO 3200 in very bright light and the shutter speed to 1/4,000 sec and see if the camera(s) choose(s) ISO 100. And then we can try to figure out if my new working theory is right by comparing those same settings with DR 100.

I suppose I was not clear ... on cameras without a real aperture, I use P mode because of the risk of ruining images by hitting various limitations of exposure.

Which means that the camera chooses everything. In very right light, it always chooses ISO 100 and some combination of shutter and aperture to get a good exposure. As light dims, it raises ISO as necessary, and after 400 ISO I still get decent DR400 results, which means that I have no reason to shoot any other way.

I didn't really understand the upside of shooting in the complex fashion you described. Do you have an elevator pitch for that?

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