Glad I found this post! I own several SMC Takumar lenses and I am considering buying a Sony A6400 or A6500 and want to adapt them to the new camera. Searching the internet, I found a lot of semi-helpful information. Mounted on the ES, the SMC lens allowed full aperture metering with set aperture sensing, and then automatic stopping to the set aperture when the shutter was released, a leading-edge development at the time. As part of this feature, the SMC had extra "tabs" on the lens mount that can interfere with the adapter (see photo, tab circled in red). Many people don't recognize this and those that do, recommend "flangeless" adapters but I could not find anyone to recommend a specific one. So, I have bought 2 different ones, since they are not that expensive, to compare:
1. M42 to e mount, K&F Concept Lens Mount Adapter
amazon.com : M42 to e mount, K&F Concept Lens Mount Adapter M42 Lens to Sony NEX E-Mount Camera for Sony Alpha NEX-7 NEX-6 NEX-5N NEX-5 NEX-C3 NEX-3 : Camera & Photo?tag=pentaxforums-20&
2. Fotasy Copper Adjustable M42 Lens to Sony E-Mount Adapter
amazon.com : Fotasy Copper Adjustable M42 Lens to Sony E-Mount Adapter, Compatible with M42 42mm Screw Mount Lens & Sony E-Mount Camera NEX-5T NEX-6 NEX-7 a3000 a3500 a5000 a5100 a6000 a6300 a6400 a6400 a6500 etc : Camera & Photo?tag=pentaxforums-20&
The K&F costs twice as much but appears much better made. The flange inside the screw mount does not interfere with the tab on the lens so it screws on fully. While mounted, the Auto/Man switch on the lens does not seem to have any function and moving the aperture control moves the aperture all the time so it works just like an old manual lens.
The Fotasy did
not allow the lens to screw on completely before the tab hit the flange. I had to machine out some of the flange and then it fit OK. One benefit of not having the flange: now the aperture is wide open, regardless of the aperture setting, with the switch in Auto. Switching it to Manual stops the aperture down to the setting.
So, I could see operating a new camera thusly: set the aperture, with switch in Auto and aperture wide-open, focus and frame. Switch to Manual and take the picture.
Anyone had experience with these and able to comment? Especially regarding removing the flange to gain the ability to switch between wide-open and set-aperture using the Auto/Manual switch.