I'm just starting to experiment with focus stacking using a rail to adjust the camera to subject distance but in my very first test setup I encountered something that made me go D'oh and now I'm not sure if it is an issue or not.
With a fixed magnification, moving the camera closer to the subject makes the subject appear larger! (who would have thought that?!?!). Here is an example where I have moved the camera about 40 mm from the nose of the car to the tail of the car.
These images are straight from the camera and scaled identically, and the image where the camera was closer to the subject is obviously larger.
My big question is will this change in subject size confuse typical focus stacking algorithms? And/Or should I change my set up (move further away) so that the change in subject size is minimized? Or would adjusting the zoom to keep the subject the same size be better? (I'm not sure how coupled the zoom and the focus are - but doing so would change the geometry of the setup)