Looking down through the stack of layers, a calculation of the cumulative effect of all the layers is done on a pixel-by-pixel basis, which yields the final view.
So is there anyway to know what effect a blending mode will have when you have lots of layers, or is it just trial and error?
It need not be trial and error, for sure.
Each layer affects what is underneath it. So, if you start off with a "normal" image on th ebottom layer, the first layer on top of that will have a specific, predictable effect, giving a "resulting image". The next layer has an effect on that resulting image, and so forth.
You rarely achieve useful results by simply stacking copies of an image with different blending modes. There are many techniques that require a copy of an image, with a particular filter applied, with a specific belnding mode and opacity.
Often a degree of trial and error is involved, but this is generally backed by experience and "feel" for the tools, rather than a magic formula.
For example [just thought I’d better give one]:
If you want to increase the colour density of a picture, you might do the following: Select all [ctrl-A].
Copy [or Copy Merged if you have lots of layers].
New layer [on top].
Paste.
Set blend to Multiply.
Set opacity to 50% [controls density adjustment].
Of course, there are at least 3 other ways to do this in PS, but this serves as an example.
The part I’m confused by is, if it is simply 2 layers and you apply the blending mode to the top layer, it shouldn’t be too hard to predict how the blending mode will effect the bottom layer.
But if I have more layers, say 15, and apply a blending mode to the top layer, now this blending mode will affect the pixels on the layers beneath it. Is this how it works, or am I still not getting it? If this is how it works, how can you tell how a blending mode to the top layer will affect many layers beneath it?
Thanks for your help!
Each layer affacts just what it "sees" below itself. It doesn’t know if there is 1 or 101 layers there. It just "sees" the result of their cumulative action.
