Hi, interesting question, i can’t figure how to use the tonemap node too… i think it’s not a tonemapper for enhancing renders , but rather a tool useful for creating hdr from photography, i’ll explain…
By the way, i think that node is not related with gamma correction / linear workflow, my guess is that the gamma parameter is there because you need to specify the gamma of your input image for the tonemapper to work .
(Warning! theese are my guesses and opinions… be doubtful and please correct me if i’m wrong!!)
What i learned about tonemapping is that can mean different things :
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generally speaking , various operations that involve ‘mapping’ -meaning adjusting/changing- the lightness value of an image to make it more pleasant or correct for the human eye.
(Linear workflow technically is a tonemapping operation, but in practice, means doing a very different thing -that is making your render do the right math when calculating light ) -
a tonemapping compressor is a filter apllied to a photo or render , it compresses the extension of light values of an hdr image (floating point) to a ldr range (8bits per channel)
-a tonemapping enhancer is also a filter , it does compression but also uses local contrast and lightness adaptation to produce a distinctive look ( those cool photos that look like paintings )
So -if i’m right- when you render with blender internal ,yafray or vray , the renderer does sort of a compression tonemap internally to display the output on your monitor (again this is indipendent from linear workflow)
if you don’t have excessively bright or dark areas then the compression is already good .
If you do have this problems you can do the same job as a tonemapper with rgb curves , levels or bright/contrast . i found those much easier to use than tonemap node (tutorials / threads is saw around seem to confirm this)
Also remember that all biased renderers perform their tricks and adaptations, so if your picture has a very bright area is very likely that all details in that area have been skipped and you can’t get much more info by tonemapping it (even if the output is hdr!)
I think compressor tonemappers are most useful for real photography where you can have a huge range of values with hidden informations.
Tonemappers with enahancing features -instead- are very cool for postproduction of renders ! i think the node included in blender is just a compressor , but give a try to theese open source projects :
qtpfsgui : standalone tonemapping utility similar to the commercial photomatix , has lots of various algorythms for tonemapping, some are easy to use and/or do local enhance.
LDR Tonemapping : (by Nasca Octavian PAUL) very interesting little utility : a ldr tonemapper ? yes… because it’s focused on local enhancement and unsharp masks - of course not on compression.
Okay , i hope i’m not totally wrong and just confusing people !.. and i also hope some coders are interested in implementing some similar enhancement node in blender : )
(ps i posted no links because they blocked my post for anti spam reason - being my 1st on this forum)