I have a Sony A6500 APS-C camera using a Sony 55-210mm lens.
I wanted more scope and so I rented a Sigma 18-300mm lens to use with a Sigma MC11 adapter.
By testing this configuration, I get an identical picture with the Sony lens at 200mm and the Sigma at 300mm.
The Sigma lens setting on 200mm gives a wider-angle picture compared to the Sony 200mm lens. It seems that the cropping factor of 1.5 is revised when using an adapter.
Why does the Sigma lens seem to have different focal lengths for the Sony lens? Is this caused by the adapter?