Hi, I have a Tamron Adaptall 85-210mm F4.5 lens and have no idea which mount to use to that I can start using on my NEX 3. Please help.
I believe the difference between the two Adaptall mounts had to do with how much info was passed from the lens to the camera. When used on the NEX it wouldn't matter which Adaptall mount you used, the adapter isn't going to pass any info to the camera anyway so go for the cheaper Adaptall option. So it's going to go like this- Lens>Adaptall mount>NEX adapter>camera body. Really doesn't matter what Adaptall camera mount you use, just get the corresponding NEX adapter. E.g.- if you have an Adaptall mount for Pentax, get a Pentax-NEX adapter and you're golden.
The adaptall2 could pass max aperture info to the camera. For the NEX system, not going to help, so either mount would work. If all you have is the adaptall lens, and no intermediate adapter, you can go straight from Adaptall->NEX
In the 70's an aftermarket lens manufacturer (Tamron) had a ground breaking idea to get a bigger slice of this market. Instead of making a lens for each brand (Canon, Nikon, Minolta (now Sony), Olympus, etc. all with different mounts), they decided to make various replaceable "rear ends" for all their lenses that correspond to these various interfaces. This was no small feat because all these different brands had different mechanisms that actuate internal apertures for Auto-Aperture modes. They called the system Adaptall, later to be followed by Adaptall2. The system worked really well, but what made it a success was that Tamron actually made really good lenses - especially the primes. They had some excellent zooms as well, but some not so good ones too. Tamron now makes aftermarket AF lenses for DSLRs but they've had to ditch the Adaptall system because (I'm speculating) that today's electronically actuated AF lenses cannot be bridged as easily or cost-effectively.
