- [Instructor] When you change the opacity of a pixel
to reveal the pixel behind it,
you're blending the combined color and luminance values
of those two pixels together.
In this default case,
an amount of the background pixel is revealed,
depending on the alpha channel level
for the foreground pixel.
Blend modes as used in Photoshop
and a great many other applications
use mathematics to combine the values
of the foreground pixel with the pixel behind it,
in a number of different ways.
There's a long list of types of blend modes
and they're usually grouped together
to make it easier to manage them.
Options to do with lightening pixels or darkening pixels
are grouped together for example.
When you choose no special blend mode,
the default option is normal.
Let's look at a couple of simple examples
to illustrate the more advanced modes.
Lighten mode simply means pixels in the foreground
that are lighter than pixels
in the background are displayed.
If the background pixel is lighter that pixel
is displayed instead.
As you might guess, darken does the opposite.
Only showing pixels in the foreground image
if they're darker than the pixels behind them.
There are much more complex blend modes than these.
And the results can vary enormously.
The best way to learn about them is to try them all out
with different layered images
while keeping the Adobe help onscreen to read up
about the effects of each mode.