Is it even possible to match every technical aspect between render engines anyway?
@lupaz I dont think so, nor is it entirely important - what I find important is parity between materials. You should be able to change lighting based on preference and if the materials are setup correctly (PBR for example) then you know you can adjust the lighting/tonemapping to taste without borking something else along the line.
Well, always though Vray and corona photographic exposure settings would match but after quickly looking at it a bit closer, it does not seems to be the case. I'll try to dig a bit further if I find time.
@Fluss I think your first thought was correct, so you are not going crazy :) I found that with some testing this morning 1600 - 12800 is exactly 3 stops. Thanks to @cjwidd and @maru for posting the thread on the vs EV thread I was able to use the excel sheet to do the conversion and it seems correct to me.
Vray 1600 ISO / 0 Exposure
Vray 1600 ISO / +3 Exposure
Vray 12800 ISO / 0 Exposure
Corona 1600 ISO / 0 Exposure
Corona 1600 ISO / +3 Exposure
Corona 12800 ISO / 0 Exposure
Just an FYI if you are trying to follow along in Corona, I had to switch this to a Physical Camera as the Corona Camera was giving me strange results. Not entirely sure why - maybe its just because I always use Physical Camera for vray/corona and used to the setup.
edit:
My conclusion is that I still think the ACES workflow is producing the result that is most similar to photographic workflow (lightroom). Where if you have a well exposed image with no crushed areas then you should be able to push the light either way without compromising your highlights somewhere (actually more so since we are working in 32bit float). Similar to how you can blow out the fstorm render and then pull it back with the burn setting, this is impossible with Corona's highlight compression.