Do Micro 4/3 lenses take in less light than APS-C lenses? (and other lens questions)

xxbluejay21 · Nov 16, 2011

I am planning on getting the NEX-5N, and I was looking for some lenses to get. I'm planning on getting the kit lens and the telephoto lens both from sony, but I was looking into some other lenses using adapters, and I came across some questions:
1. Are all non-sony lenses manual focus? Is there any sort of electronic adapter for the nex yet (besides alpha lenses)?
2. If I get a nex to micro 4/3 adapter, will a 4/3 lens cause vignetting? What are other cons to a lens like that?
3. for nikon f mount and canon fd, what kind of mount is that?? If I get a nex adapter for that, will it work like if I were to get a nex-EF adapter and use an EF lens on it?
4. Most important question!!: Is a 50mm f/1.2 FD LENS and a 50mm f/1.2 4/3 MOUNT LENS and a 50mm f/1.2 EF MOUNT LENS all the same? Do they all collect the same amount of light? Thinking logically I would conclude that because the 4/3 lens is smaller that it would collect less light, but I don't know anything about the inner workings of a lens. If I put a 4/3 mount lens on the NEX and then I put on an EF mount lens and set them both to f/1.2 at night, would it be the same brightness?

Thanks for answering. You guys rock!

enzodm · Nov 16, 2011

F-number is the focal length divided by the diameter of the hole where the light enters, so in principle they are all the same. However, consider that a lens for a smaller sensor needs to collect light for a smaller surface, so you may incur in some vignetting when using a lens made for a smaller sensor on a larger one.
On the other side, a lens made for a much larger sensor (e.g. medium format) might have less resolution when used on a smaller sensor.

Apart from this, the amount of light, which in principle is the same, in reality depends also on transmission factor of glass used in lenses, so may be slightly different for different lenses, but not depending on sensor size -just a property of the lens itself. I never crossed specific data on this (I collect and use old lenses).

Regarding adapters, consider that no one (as far as I know) transmits data for autofocus, aperture, etc. So you will use other lenses manually, and this also means that lenses should provide an aperture ring.