S-Mount với kích thước nhỏ và giá thành thấp.
There is no regulation of flange back.
S-mount are used for compact cameras and board cameras. Currently, there are many lenses with small size and low price.
S → C mount conversion ring is also on sale.
C mount has provisions of flange back, whereas S mount does not have flange back specification.
Therefore, even if the aperture is changed, It doesn’t mean that C mount lenses can be used.
When using the C mount lens, I think that it is necessary to try it.