Lens question

[pbourke]

I have a large number of small objects to be reconstructed.
I've done a few using the Canon 100mm but that is a 1:1 lens and only works well for objects down to 2cm long, on a full frame sensor.
I would like to know whether 1:2 or 1:5 lenses can be used. For example the Laowa 60mm or Canon EP-E 65mm, see
     https://www.venuslens.net/product/laowa-60mm-f2/
and
     https://www.canon.com.au/camera-lenses/mp-e65mm-f-2-8-1-5x-macro
This is where my knowledge of optics and relation to MetaShape are deficient. They are both a single focal length, but can zoom from infinity to close range, and I believe the image size changes significantly during focus.
Anyone understand this stuff?

[Arie]

Hi pbourke,
the focal length of a lens can change when adjusting the focus. This is a well-known effect named "focus breathing".

In general, I usually use only manual focus, i.e. I stay at a constant distance to the object-of-interest. If I need some additional close-up shots, where I am required to refocus, I create a second calibration group for the images with the adjusted focus in Agisoft to compensate for the change in focal length.

Hope that helps.
All the best,
Arie.