It depends on cameras what you use.
There are 3 image circle sizes for Entaniya Fisheye 250 MFT.
If you use the lens as a circumference fish eye lens, the ways to make image circle fit perfectly are as below.
Micro Four Thirds：Entaniya Fisheye 250 MFT 3.0
APS-C：Entaniya Fisheye 250 MFT 3.6
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