Hello Everybody, i'm having problem with some artifacts on the surface shaders with tif/jpg textures after rending, it gets this pixelated look on the blacks. (see img1)



I'm working with linear workflow from the render settings.

Render settings> common
Enabled color management
Default input profile: Linear sRGB
Default output profile: sRGB
(i also set the color profile to sRGB on each file texture)

File output
image format: HDR

Render settings> quality
framebuffer
RGBA (float) 4x32 bit
Gamma 1.0
colorclip: Raw

I just make a polygon plane and attach a surface shader with a file texture, that's all..
for rendering i'm using Mental Ray and no lens shader is attached to the camera. i tried to change all the settings in the render settings, but nothing worked.

Using Physycal sun and sky, with FG. and a few spotlights.

does anyone know what could be happening here?

thanks a bunch.

Nic

hard to seay but yes a jpeg artifact can really blow out when roundtripped source -> linear -> filter-> source space.

thanks for the reply Joojaa, however i dind't understand what you mean.. can you describe a little more?
tahnks again!

When you set:

Default input profile: Linear sRGB
Default output profile: sRGB

what your saying is that the color in a image is havinga  2.2 gammacurve that is to say that the images midtones are reallly exagarated while very bright and dark colors are the same. now if there happens to be any small residue in the image in the empty area (theres boud to be because ist a jpeg and jpeg artifacts are a bit of a problem) then when you filter (blur or sharpen) as part of the rendering process (because the image gets multiampled) any tiny bleed can suddenly boos up in the process.

Down to linear (high midtones get darkened) bleed unnoticable but you boost it back to gamma of 2.2

So even if the jpeg artifact is nearly unnoticable as a image it can get boosted up by teh combination of theese things PLUS any additional background, since even a slight change under theese sircumstances can become more porminent.

Theres also a second thing taht may be going on, mayas uusing the image as straight alpha, whereas the image most likely is in form of premultiplied alpha (while yes its straight in PS, PS unlogically allways saves as premultiplied alpha)