Here's a schematic of the blending layer and the
base layer.
| Blending Layer
Pixels |
|
|
|
| |
|
|
|
| Base Layer Pixels |
|
|
|
| |
|
|
|
| Photograph Looks
Like This |
|
|
|
White (255,255,255) pixels in the blending layer create no change.
Black pixels (0,0,0) in the blending layer or in the base layer result
in black.
That's because when you multiply anything by zero (and black is 0,0,0,),
the result is zero (0,0,0).
Step Wedges
Step wedges can help you understand what a blending mode is doing.
The top step wedge is the original photograph, and the lower step
wedge is with the Multiply blending mode.
| Normal |
 |
| Multiply |
 |
| |
(0,0,0) |
(128,128,128) |
(255,255,255) |
Go to Step Wedge - The Understanding
Tool.
You can use the Multiply blending mode to darken an overexposed photograph.
For example, here's an overexposed photograph of a glass block.
The blending mode of the Background copy was changed to Multiply.
Below, the original is to the left, and the version with the Multiply
blending mode is to the right.
Original
With Multiply Blending Mode
What Happened Above?
Let's answer that with some analogies, and some math.
Analogy
Imagine putting two slides of the same scene in a slide projector
together.
The dark areas of the scene will become darker, while the lighter
areas remain the same.
Mathematics
You can skip the math if you wish.
Go to Opacity.
Let's look at the math for one pixel, say, one along the bottom edge
of the above photograph of a glass block.
Let's call this pixel Egor.
The RGB value for this pixel is
30,32,31.
The RGB values for Egor are the same on the blending layer and the
base layer.
| Blending Layer
Pixel |
30,32,31 |
| |
|
| Base Layer Pixel |
30,32,31 |
That's because the same photograph is on each of the layers.
The RGB values for the blending layer Egor are multiplied by RGB
values of the corresponding Egor in the base layer.
|
30 |
x |
30 |
÷ |
255 |
= |
4 |
|
32 |
x |
32 |
÷ |
255 |
= |
4 |
|
31 |
x |
31 |
÷ |
255 |
= |
4 |
The new RGB values for Egor are
4,4,4.
Egor is darker.
In RGB values, 4,4,4
is darker than 30,32,31,
the original value of Egor.
You can reduce the effect of a blending mode by reducing the opacity
of the blending layer.
With Multiply Blending Mode
With Multiply Blending Mode
And Opacity Reduced to 50%
Use More than One
You can add more than one Multiply layer to darken more.
There are brief descriptions of the other Top-Transforms-Lower blending
modes in the next section.
