Problem with camera positions

[pbourke]

I'm a fairly regular used of MetashapePro.
Today I used a 100mm Canon Macro lens on Canon5D MKIII to capture a small nut.
On a tripod, in good light and high aperture, 75% of surfaces closest to the camera is in good focus.
I used a motorised platter, 20 degree steps around 360 degrees and 4 heights.
I created masks, but actually it didn't make any difference to the problem.
What I get can be seen in the attachment showing the sparse point loud and camera positions, part of the capture wedge camera positions are rotated around to overlap with another section of the 360 camera array.
Ideas?
Is a perfect 20 degree capture some sort of pathological case?

[Alexey Pasumansky]

Hello pbourke,

Can you please send the project file in PSZ format (Metashape Archive) with the alignment results to support@agisoft.com?

[pbourke]

Thanks for the reply.
Actually, I did a quick lens calibration and it seemed to fix things.
Will do a better calibration tomorrow and see what happens.

[pbourke]

I can confirm, after doing a careful, 15 shot camera calibration the issues seemed to have disappeared. As an example see
    https://skfb.ly/6IwyC
This "nut" is less than 1cm across. While the mesh detail isn't obvious from this, it is extremely good.
So I'm keen to understand why, using the 100mm Canon Macro .... does it mean the internal model for narrow macros isn't a match to reality?
Will repeat the calibration next with the same lens but another 100mm of extension tubes.