hi, On Fri, Feb 24, 2017 at 6:20 AM, Stéphane Gourichon <[email protected]> wrote: > Hello, > > Darktable exposure fusion released after 2.2.0 is interesting. I tested it, > and as expected it brightened pictures a bit like draco tone mapping > operator but with more natural colors and different style of controls. > Great! > > LWN wrote about it in A look at darktable 2.2.0 [LWN.net] that (emphasis > mine): > > In scenarios where the dynamic range of a scene is too wide to be captured > in a single shot, the photographer can shoot multiple exposures (e.g., one > to capture the highlights and one for the shadows). Those exposures can then > be combined via darktable's new "exposure fusion" module. In essence, the > two frames (or however many were taken) are stacked together, > > > The link is to > https://www.darktable.org/2016/08/compressing-dynamic-range-with-exposure-fusion/ > > I'm somehow confused because the latter link processes only one picture at a > time. > > Please explain if the following assertions are right or wrong and explain: > > * Darktable basecurve fusion always considers only one image at a time. > Never "two frames", several input files (be it bracketed exposure, flash/no > flash, etc.).
yes. > * Darktable basecurve fusion implements > http://web.stanford.edu/class/cs231m/project-1/exposure-fusion.pdf in the > restricted case where "sequence" is actually a copy of the same input data > with digitally boosted exposure. yes. > * Darktable applies "traditional" basecurve upstream (i.e. before, or > "first, then fed into") of Mertens/Kautz/Van Reeth algorithm. yes. > * In traditional darktable basecurve, the output values for any pixel in > output image only depends on the input value of that same and only pixel in > source image, not any surrounding pixel. without exposure fusion, yes. > * Darktable basecurve fusion is not reducible to an overall "meta-basecurve" > because, following Mertens/Kautz/Van Reeth algorithm, it considers the > neighborhood of each pixels in deciding which pixel to take, a kind of > operation that traditional basecurve does not perform. yes. > * As a consequence, darktable implementation provides the benefit of the > algorithm in term of rendering perception (preserve natural colours, etc), > but not the improved noise in dark area of the flash/no-flash option, since > there is only one input image. That would either need preprocessing of the > whole algorithm before darktable, or feeding several pictures into darktable > to implement the whole algorithm. yes. > Thank you in advance for clarification! Probably a number of people will > benefit. cheers, jo > -- > Stéphane Gourichon > > > ____________________________________________________________________________ > darktable user mailing list to unsubscribe send a mail to > [email protected] ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to [email protected]
