Am Freitag, 11. März 2016, 16:25:09 schrieb Denis Testemale: [...]
> Le 11/03/2016 16:02, Pascal Obry a écrit : > > 2016-03-11 15:48 GMT+01:00 Denis Testemale <[email protected]>: [...] > >> - deactivated all parameter (auto blabla, local contrast, highlight > >> recovery, etc.) which could modify the luminosity of pixels > >> - used only the exposure compensation with 0EV, +2EV and +4EV > >> respectively > >> - and finally checked visually (which is subjective and prone to errors) > >> and quantitatively by measuring the RGB values with the sampling tool. > >> With the 3 softwares, the three images are identical in terms of > >> exposure/luminosity/RGB channels . I'm not talking about the noise, > >> obviously. This is logical to me (and to you also I guess :-) ) and > >> means that the 3 software define the exposure the same way. This was my > >> point in previous messages when I said that it is an 'absolute' physical > >> value. I can check, but I'm very confident that it is the same for LR. > > > > But again this is exactly what I did with Lr when I was mapping the > > .xmp and the exposure > > was not taken into account the same way. Strange as it is, it is the > > truth. I would have loved > > avoiding all this work by just using the Lr values in dt. The same was > > true with exposure. > > > > I was using Lr on Virtual Box on half screen and dt on the other half > > for easy comparisons. Did you also export pictures and sample the pixels? That might be more precise than relying on the video stack of a virtualization layer. > > Note that for exposure the offset is not that large, the mapping is > > > > defined like this: > > lr2dt_t lr2dt_exposure_table[] = { { -5, -4.5 }, { 0, 0 }, { 5, 4.5 } }; > > > > That is -5 on Lr map to -4.5 on dt. 0 is 0 and 5 is mapped to 4.5 and > > the mapping is linear. > > > > I don't remember all the details, this is a long time ago but IIRC I > > was matching the highlights > > for the 5 vs 4.5, maybe Lr is always doing some hightligh recovery > > that dt does not. If that's the reason for the exposure scaling I think we should ignore it. Using exposure to compensate for unrelated changes is IMO very bad™. It seems we need someone with access to Lr to help us debug this for real. > > Regards, Tobias
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