Shadows displaying "mesh" in .crw file.

[asoulym]

Hi, was editing a Canon G12 raw file today in ACR, sent it to CS5 as a smart object and it turns up with what looks like over-lapping mesh, horizontal and verticle lines of varying thickness, and dark grey in color, in the shadows. Never seen it before, but it disappeared when I flattened the file. If I overly darken it to the point of complete black, the lines become very regular, thin ones inside a pattern of thicker ones covering the whole file.

  Any ideas what it is or what caused it

[NikoJorj]

Banding, aka pattern noise?
A common problem with canon sensors I'm afraid...

[asoulym]

Thanks NikoJorj

Why would it show in this particular file, having done nothing out of the ordinary to it, processing wise.

[NikoJorj]

Higher ISO, under-exposure leading to the same effect (particularly if you use AutoTone), higher temperature maybe... hard to tell without knowing more.

[Keith Reeder]

Banding, aka pattern noise?
A common problem with canon sensors I'm afraid...

Just for the sake of balance, I've only ever had banding from Nikon bodies...