jpgs produce image loss in renders

[fooprobe]

i found a weird bug: using jpgs in material transparency can produce image loss in the render, even if there is no image loss in the jpg itself.

here's a render using the same image as a transparency map. the material rendered on the left uses a jpg as transparency, the material rendered on the right uses a png. you can see the "chatter" around the image rendered on the left but not the right. the jpg was saved with maximum quality from photoshop and does not show the visible chatter when opened again, it only appears in the rendering. png and jpg are also linked below.

i guess i'm not saving any transparency maps as jpg anymore.

this only seems to occur in the transparency maps of standard material layers (diffuse and emissive), not the Vray BRDF layer's "opacity" map.

version 2.00.26563 edu

[fpedrogo]

Yes, I believe it has to be with the jpg compression. Unfortunately, we could not change that in V-Ray 2.0 and I believe it is set to 80%. Better use other format like exr or tiff. Png work fine if you do simple color correction.

[fooprobe]

ok, at least it's a known issue. thanks!