focus throw is on many fine lenses. If you have a lens you really
love for focus stacking and it has a short focus throw, you may
have to use a rail. The wonderful Coastal Optics 60mm f/4 APO
lens has too short a focus throw for a 60mm macro IMO.
Watch the Light
This is more of a general photographic concern rather than limited
to focus stacking. Pay attention to the light in your frame. If you
have variable light, like a shaft of sunlight in a shady place, you
may want to modify that shaft of light with a diffuser. I have thrown
out more stacked photos because I could not nicely tone down hot
spots where clipping occurred than for any other reason. Carry
some small translucent diffusers with you and figure out some way
(and it is difficult) to position them to filter the hot spots while you
step through the focus stacking. The same goes for specular
highlights (bright reflections). Tone them down in the field and don’t
count on post-processing to be successful in removing or modifying
them well.
Front to Back
Another very common mistake is to not catch the very tip of the
front of your subject. You get back home and find a perfectly-
stacked photo except that the front- most part is out of focus. It
happens a lot. As a rule I back off until the whole thing is out-of-
focus and creep up until just before the tip of the top of the front of
the subject appears. I stack from there inward.
Extraneous Stuff
Another way to ruin a shot is to have too much room between the
very front of your subject and the subject itself, like a blade of grass
in the foreground or a stick, etc. If you can include the grass or stick
in the composition (and resolve it), fine, but this is perhaps the most
common way to produce large and un- fixable artifacts – a bridge
too far. I remove or tie back whatever is intruding in my shot. Yes,
Photoshop CS5 can remove extraneous objects pretty well, but so
can you and perfectly.
Sensor Cleaning
Cleaning your sensor takes on another whole meaning when you
focus stack. That spec of dust on a single- shot photo becomes a
long line when 15-20 layers are stacked, a line not always easy to