* Archie Macintosh <archie...@gmx.co.uk> [01-31-20 15:37]: > That's interesting, Matt. So, let's say I want to edit an > out-of-camera JPG file in darktable (which can be useful for Fuji > shooters!); is it advisable first to convert the JPG to, say, a 32bit > TIF before editing it? > > mac > > On Fri, 31 Jan 2020 at 19:09, Matt Maguire <matthew.magu...@gmail.com> wrote: > > > > The thing is, you have a limited number of bits per pixel, and human > > perception of changes in brightness fall off logarithmically as things get > > brighter. So, to make sure you get the most “bang for your bits”, you want > > smaller quantisation steps for low intensity and bigger quantisation steps > > at higher intensities. L*a*b achieves this by using a (non-linear) gamma > > encoding. > > > > In the case of linear RBG, if you use floating point numbers, they consist > > of a mantissa and an exponent (like in scientific notation), so as things > > get brighter, the quantisation steps naturally get larger due to the fixed > > precision of the mantissa. So, using floating point numbers for linear RBG > > representations is actually pretty important. > > > > On Sat, 1 Feb 2020 at 2:03 am, David Vincent-Jones <david...@gmail.com> > > wrote: > >> > >> darktable's use of floating point calculation, as I understand it, was > >> important for maintaining accuracy through L*a*b processing. Is this > >> still valid as the emphasis in processing shifts to RGB? The reason that > >> I ask this is to question whether RGB modules still are greatly helped > >> by the use of OpenCL. > >> > >> ____________________________________________________________________________ > >> darktable user mailing list > >> to unsubscribe send a mail to > >> darktable-user+unsubscr...@lists.darktable.org > >> > > > > ____________________________________________________________________________ > > darktable user mailing list to unsubscribe send a mail to > > darktable-user+unsubscr...@lists.darktable.org > ____________________________________________________________________________ > darktable user mailing list > to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org
the computations withing dt are floating point. number base of the image file is not a concern. two different points. and any conversion may introduce differences to original image, ie: the converted image in not an original, but a close representation of the original. ps: your chosen email client does not wrap lines so what you see is what you get. -- (paka)Patrick Shanahan Plainfield, Indiana, USA @ptilopteri http://en.opensuse.org openSUSE Community Member facebook/ptilopteri Photos: http://wahoo.no-ip.org/piwigo paka @ IRCnet freenode ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org
