Thanks, that's what I thought. The white trick was actually what I had decided to try on the next job. It'll get 90% of the way there so I figure that's the best one can hope for. It's definitely better than assuming black and experiencing all of the saturation and luminance shifts as you point out Andy.
Just accepting them is out the question but in this scenario it's going to flame to comp over a pretty much white background anyway with maybe a light vignette. I wanted to make sure I wasn't going crazy. :D I guess I *could* ask the flame artist to comp the footage in linear space but I always get really nervous when I send off footage and can't review it before it goes on air to make sure they are handling it correctly, I would much prefer something which has the least possibility of being botched somehow. - Gavin On Tue, Nov 15, 2011 at 12:28 AM, Ivan Busquets <[email protected]>wrote: > Hi Gavin, > > As you said yourself, the equation cannot be solved UNLESS you know both > variables on one of the sides. > In other words, you'd need to have the BG image in order to prep a FG > image so it can be comped in sRGB space and match the results of a linear > comp. > > So is there no way to output a PSD or PNG or TIFF which will look the same >> as my composite in Nuke over a white background? > > > If you need to get the same results on a white background, you could prep > your FG element such that: > > X = ( (FG * alpha + (1 - alpha)) ^ 2.2 - (1 - alpha) / alpha ) ^ > (1/2.2) > > Where X is the FG image you'd want to export to be comped on a white BG. > But of course, this will only give you a match when comping the FG over a > WHITE BG. If the BG changes, then you'd need to prep a different FG to go > with it. > > Hope that helps. > > Cheers, > Ivan > > > > On Mon, Nov 14, 2011 at 12:13 PM, Gavin Greenwalt <[email protected] > > wrote: > >> How are Nuke users handling workflows in which they need to deliver >> images with alpha that will be composited in sRGB space not linear space? >> >> Essentially we have a situation where you would need to find equations >> for u and v such that (xy + z(1-y))^(1-2.2) = (uv + z^(1-2.2)(1-v)). >> >> My initial impression is that it's impossible since the simplified >> version of this conundrum would be (x+y)^2 = (u+v) which I believe is >> mathematically impossible to solve... right? So is there no way to output >> a PSD or PNG or TIFF which will look the same as my composite in Nuke over >> a white background? >> >> Thanks, >> Gavin >> >> _______________________________________________ >> Nuke-users mailing list >> [email protected], http://forums.thefoundry.co.uk/ >> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >> > > > _______________________________________________ > Nuke-users mailing list > [email protected], http://forums.thefoundry.co.uk/ > http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >
_______________________________________________ Nuke-users mailing list [email protected], http://forums.thefoundry.co.uk/ http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
