> PHOTOSHOP USER>^ APRIL 2020[ 92 ]
This effect uses the Maximum stack mode, one of Photoshop’s statistical tools for
image analysis. Like all stack modes, Maximum considers the value of each pixel on
each channel in the context of an entire stack of layers. While our example here will
only use a handful of layers, stack modes can operate on hundreds of layers with
reasonable efficiency. Maximum compares the pixels on every layer, and chooses the
maximum from each, which is perfect for this look.
Just for a quick example of how this works, check out these overlapping circles.
Each circle is on its own layer, and is a “pure” RGB color. Using Maximum, the overlap
behaves like the Linear Dodge (Add) blend mode. The difference is that blend modes
consider the blended layer with whatever is below, calculate a result, and then send
the output to the next layer up. Stack modes consider all the layers together at once,
and they ignore transparent pixels.Step One: Now that we know what to expect, let’s generate some star trails behind
this giraffe grabbing a late-night snack. The sky has some beautiful cluster features,
but if we blur them, they’ll become a blobby mess. (If you’d like to download the low-
res watermarked version of this image to follow along, click this link, log in with your
Adobe ID, and click the Save to Library button. Double-click the image in the Libraries
panel [Window>Libraries] to open it in Photoshop.)SCOT TVALENTINE
Photoshop Proving Ground
Creating star trails in nighttime photos doesn’t have to commit you to an evening of caffeine and
chills, where your series could be ruined by a stray set of headlights or a dead camera battery. While
dedication certainly pays off, for some of us a more tactical (or lazy) approach is just fine. Let’s use a
single image and synthesize the effect, all inside Photoshop.CREATING STAR TRAILS
Circles beforeCircles blended with Maximum©Adobe Stock/Katrina Brown