Focus stacking: Changing focus vs. Macro Rail

Larry,

There is a special class of lenses that the apparent magnification doesn't change with lens to subject distance, they are "Telecentric". Many of the quality microscope objective infinite type lenses (requires a tube lens), such as the Mitutoyo are close to Telecentric. These become very valuable when you try to do Stack & Stitching, since the subject magnification must remain very similar between stitches.

This may be beyond the scope of your thread, but wanted to make you aware of these lenses.

Also as you go to higher magnifications, results tend to favor moving the camera lens to subject distance rather than using lens internal focus.

Best,

Larry Cunningham wrote:

Many thanks, R_U_Q_R_U, for the detailed response and the links to further information. I suspected that the answer to my question wouldn't be simple, and you've confirmed my suspicions.

I tried to visualize the scene from the camera focal plane as I changed the focus point (in the case of the camera simply mounted on a tripod) or changed the camera-to-subject distance (when using a macro rail). In both cases, the perspective changes, as well as what is and isn't visible in the image frame. I can understand how the two approaches each have their own advantages and disadvantages, depending on the target.

I'm looking forward to diving deeper into the subject and doing my own experimenting with the techniques. Looks like a fun way to keep photographically involved when the weather outside is frightful.

Larry