Sony Cameras - a very brief history

Sony did make a series of "A" mount DSLR cameras (such as the A77 ii) As they transitioned to "E" mount lenses, they introduced (in 2020) an A mount to E mount adapter. Curiously, Sony does not call their DLSR cameras "DSLR", but rather "TSLR" where "T" stands for "translucent". They got into the DSLR business when they acquired Konica/Minolta in 2007. The A77 is an APS-C camera and the A99 is a full frame 42 megapixel camera.

Sometime around 2021, Sony bailed out of the DSLR game entirely.

The Sony A mount has a 44.5 mm flange distance
The Sony E mount has an 18 mm flange distance

Compare this to Canon where:

The Canon EF mount has a 44 mm flange distance
The Canon RF mount has a 20mm flange distance.

A statement by Canon:

"So then the question is, why a flange distance of 20mm? Slightly smaller would have given better possibilities optically, but that means the whole front panel becomes thinner. You have to make the camera thinner and smaller, therefore the front body has less strength, and because you have to use thinner metals, the screws that hold it in have to be thinner. All these things then affect durability and endurance. And if you want to hang a big lens off the front of it, you've got to have a solid front panel, with big screws that keep everything in place. So it's that balance of endurance and durability versus optical performance."