System: Windows 10 Pro (v. 1803)
Graphic card: GeForce GTX 1080 Ti
I have problems using RGBA channels of TGAs in Cycles. I want to use every single color channel of an TGA to work with it individually.
In my case I am writing greyscale informations into the channels, like bumpmap, anisotrophy or roughness. All in one file.
Following a shot with a simple setup show the problem. I've attached the blend file for testing too.
Cycles seem to multiply the Alpha channel informations into all other channels while rendering. But Blenders image editor shows the channels right.
EDIT: In the meantime I switched to TIFF files. TIFFs color channels can be read by single and my node tree works fine in Cycles.
But it would be good if you check it with TGAs and fix the problem for the future. There are a lot of people who are working with TGA.