"oil" shadows

[metroberlin]

have a problem with vray sun/sky.

our new workflow is to work with the vray sun system (multiplier at 1) and control all with the physical cam. qmc for first and LC for secondary bounces. works perfectly and I am very satisfied with. now we get a problem sometimes with area shadows. they look like an "oil film". the shadows from the image below are from a plane with opacity but the same happens with geometry trees. this unwanted effect just disappears once we lower the sun to 0.1 or the size of the sun to 0.1. but both things have also an effect on the rest of the scene which we don´t want. does anybody knows this strange shadow problem ?

thanks in advance

ps. that also happens just with "exponentional" colour mapping. with "reinhard" it not the case. but i can´t use "reinhard" for the rest of the image

[vlado]

You probably have your "Bright" multiplier lower than your "Dark" one, which causes color inversion.

Best regards,
Vlado

[metroberlin]

indeed we have...but we can´t do it another way because then the scene would be 10times too bright. so far it worked very well with dark:5 and bright:2 values. any other chance to to get rid of it ?

[jonahhawk]

it sounds like you need to work on your camera settings. increase the f-stop number or change the film speed, shutter speed etc. I'm not a photographer and don't have good advice on settings for your scene. I am still in the process of developing some sort of intuition for the PhyCam settings. I'm not always getting predictable results (due to my predictions being off, not the results!)

I try to leave teh color mapping alone, the sun set to 1.0 and only deal with lighting through the Phycam. I use the color mapping mode that the tut suggests but leave the values at their defaults.

Also i've found that I have great control over the lighting by rendering to exr and doing Gamma/Pedistal/Gain adjustments in Combustion or exposure in photoshop.

[metroberlin]

we also tried to control ALL with the cam, but the results were not always as wanted. especially with room like these where in real world also photographer would have problems to get good results. there we need to tweak the colour mapping. but maybe it´s really possible to control ALL with the cam...need to do some more tests.