I have tried all of the above software and, while they all seem to
work, each has its quirks. CombineZM is free (GPL) so you might
want to download a copy, but it lacks the polish and ease of use
(IMO) that I look for in a program. The most well-known application
that can process photo stacks is Adobe Photoshop CS4 (and
higher), which is easy to use, but it is not free and also runs very
slowly when building stacks. Photoshop’s results are not up to
some of the other software. There is a general review of focus-
stacking software later in this article, including how to stack in
Photoshop, but all of the above-listed software do more or less the
same thing, which is to align your stack of photos and merge them.
The program I use almost all the time is Zerene Stacker but all of
the above can do the job.
Software to Align and Merge
Using the software, the stack of photos taken of a subject, each at
a different focus point, need to be lined up. Every time we turn the
focus ring the whole image is enlarged (or shrunk) depending on
which way we turn it. While each layer is a photo of the same
object, these photos are enough different that they don’t just
automatically line up. They have to be aligned, one with the other.
Once the stack of photos are in the stacking software (each one in
a different layer), the program has to do two things and in this
order. First the program will align all of the different photos so they
line up with one another internally. This can take a long while in
Photoshop but Helicon Focus and Zerene Stacker are very fast.
Once the layers are aligned, then the aligned layers are blended to
merge the separate layers into a single photo which is then
flattened and saved to a hard drive. It is as simple as that although
these operations can take a long time depending on the number of
layers and the subject matter. Something with a lot of contrast and
detail is easier for the software to align than say a pile of sand
where there are not many reference objects. It all depends. Some
take seconds while others can take 30 minutes or more. Photo
stacking, like macro photography itself, is a lesson in patience, so if
you are in a hurry, I don’t suggest it. For me it has been good,
because I need to learn to have more patience and this is a fun way
to do that.