Entrance Pupil Problems with Stacking
Since I started using the Nikon D800E, I have had some minor but
annoying problems with stacking the resulting images. It has
nothing to do with the D800E, because the problem happens in the
stacking program, not in the camera. And the problem is....
The two main modes of stacking, PMax and DMap, no longer line
up perfectly exactly. There are some very slight differences
between the two modes to the effect that when I try to retouch
using one on the other, there are slight differences that make the
retouching not worth it in some cases.
The good news is that DMap by itself (with the D800E) is almost
perfect in this higher resolution. I have asked around and no one
can explain why it should suddenly be so much better.
Meanwhile, the problem of the two modes not working so well
together I took up with Rik Littlefield, the author of Zerene Stacker.
Littlefield is incredible in that he is unerringly interested in every
facet of not just his program, butall stacking and related topics. He
studied the problem and suggested the problem is the following.
In the stacks I have been doing, I place the camera and lens on a
focus rail and move the whole ensemble incrementally forward for
stacking, as opposed to fixing the camera/lens on a tripod and
turning the lens helicoid. This Littlefield pointed out can make a
difference.
He said that the entrance pupil for the lens determines how
stacking programs can handle the images. The idea situation is if
the entrance pupil in the lens stays fixed, and the camera
incrementally moves on its own. He pointed out that there is no
chance of this when we move both camera and lens together as a
unit on a focus rail, but that instead by turning the helicoid to stack,
with some lenses the results will be better. In particular lenses such
as the Nikon 35mm f/1.4G, which has back-focus this will work. “IF”
lenses, since they are internal focus lenses will cause problems
when I stacking by moving the camera and lens as a unit.
Best of all would be to use a bellows, fixing the front standard (with
the lens) and moving the camera on the back standard while the