Other side of the fence (MF Lens help)

I have been wanting to grab a prime since I sold my Sigma 30/1.4 when I got my 5D. When I have a prime in front of my camera that is when I am more creative because it forces me to move my feet and think more. Also the thin DOF are nice too.

I like that large aperture (/2.0 or larger) and was originally looking at the EF 85/1.8. Then I started looking at some of the pics in the lens sections and noticed a few MF alternative lenses (primarily M42 mount) with focal lengths between 24mm-100mm

1) What is the difference between Auto Rikenon 50mm f/2 and say Auto Mamiya Sekor 55mm f/1.8 in terms of mount.

2)They are both "M42" mount so does that mean the same adapter would work on them?

3) Are all M42 to EF Adapters created equally? I see some ranging from 6$ to 40$ and some with confirm chips.

Any other thoughts?

BTW: Also I know that I won't have AF in case anyone thinks that I don't know about that. Like I said, I am getting into a experimenting mood when it comes down to it.

Thanks!

http://forum.manualfoc​us.org/

http://forum.mflenses.​com/

A lot of very knowledgeable people there...

1: I see and know no difference. Probably one has the aperture auto pin, the other not?

2: Yes, or nearly yes: From my point of view best adapters are those with a flange that press aperture auto pin - if the lens has one. If the lens has not this pin, it doesn´t has any donwside, as far as I see.
With a flangeless M42-EF adapter you have a bit trouble with that pin, if the lens has one.
Most adapters have this flange, but not all.

3: Some adapters have a chip, some not. WIth chip you have a AF light in the camera viewfinder, that could help to focus. And you have a EXIF info. The cehap ones have for example 50mm f/2.0, but better ones could be programmed at the factory, or even from the customer. But this EXIF info is not coulpled to your lens iris - so if you programm your 50/1,4 lens adapter to 50mm and f/1.4 it even tell the camera f/1.4 when you use f/8.0.
One some of the better chiped adapters one could readjust the AF metering. Could help.

Some adapters may not be very accurate, this could end in not reaching infinity, or that infinity is not exactly on the infinity symbol on the lens. But I never noticed that up to now. I have some ~ 15 cheap adapters. And much more M42 lenses.
And I use manual focus through the viewfinder - only with my eyes and the EE-S screen on the EOS 5D classic (for the faster lenses very helpfull).

Please be carefull! Manual lenses sometimes start LBA!
But the lenses are mostly cheaper than Canon EF lenses.