/ic/ - Artwork/Critique

>>3028909
There are a couple of reasons why you'd use multiply.
The biggest is, if they use or have any white or grey on the layer, setting it to multiply will make the white transparent - the calculations of Multiply will not show any white at all. I made a quick graphic to show how this works - the black lines and greyscale bar on the right is the exact same layer as the ones on the left - the left is set to Multiply, so no white shows. The one on the right is Opacity, and the white shows.
So, for instance, if you scanned some line art in, and set the layer as multiply, ONLY the black in that image will show. Or, if you corrected a line art layer with white, instead of erasing, or the layer is filled with white, with black lines.
Capiche?