thinking of getting the nex reverse mount ring to use with a nikon 50 1.8 manual focus lens.
Question is, does this only work at a certain distance with a fixed maginification, or am I able to move back and forth and focus for different magnification. also do wide lenses generally give greater magnificaiton? thanks.

You will only have one focus point and one mag. ratio.

The shorter the focal length, the greater the mag. ratio you'll get.... up to roughly 20mm or so.

thanks sparky. that answers it.

Your next issue will be controlling the aperture.

Hopefully, your lens is not a G-style, and you have an aperture ring (such as a D lens would have). If so, order a Nikon BR-6 from a camera store.

Otherwise, you're going to have problems with the aperture being closed to f/22 all the time.

thanks. the lens has an aperture ring. Now I am wondering if its better to reverse the lens on a zoom lens. there at least you get a little more control over degree of magnification I think, or just use extension tubes.

You'll probably get more 'choices' in mag. ratios with extension tubes than you will with a reversed zoom. But with tubes, you'll need to get a set with both an aperture lever and electrical contacts if you want to maintain control of the aperture and exposure with the camera. Cheap tubes don't have these features, and it becomes discouraging very quickly when you try to skimp.

using a manual focus lens manual aperture lens, i dont think the electric one makes much of a difference. the metering actually continues to work in the nex system. It wont be my main macro rig, as I have the 5d3, mpe-65 and sigma 150 2.8 for that. just might be something fun to have.

Manual aperture simply means you have an aperture ring. Tubes without the aperture link will allow the lens to stop down at any time.. so you would need to focus and compose with the lens open, THEN close the aperture down........ THEN press the shutter release.

Yup. that is true, thought I can probably focus with the aperture at f8. Its a live view focus anyway, unless there is not enough light.