Yes, this works fine, assuming that the lens uses internal focus so that the objective does not move as focus changes.plantfan123 wrote: ↑Tue Nov 30, 2021 11:11 pmWith the lens focus method can you do movements of a few microns that you can do with the Stackshot that are so useful in microscopy? How precise is it?
A good way of thinking about the situation is that the objective makes an object that is actually small and close, look like an object that is large and distant. Then the rear lens just focuses on the large distant object, and steps focus through that. So, if the rear lens has enough precision to focus-step its way through a real large object without focus banding (and they all do), then it also has enough precision to focus-step its way through the virtual large object that is created by the objective.
From the standpoint of precision, things actually get better at high magnification, because the magnification process stretches the large-and-distant virtual object along the depth axis. Unfortunately, there is a limit in how far the rear lens can shift focus away from infinity, before it starts seeing parts of the enlarged object where the image is degraded by pulling the objective away from its design point. As you saw, focusing the rear lens at 1:1 messed up your 10X objective pretty badly. With an objective of higher magnification and higher NA, that problem would be even worse.
See my thread on "AF motor focusing with a microscope objective" for some illustration. Note particularly the behavior with 50X NA 0.55, described near the end of the first page of the thread.
--Rik