Seagull 2.3 viewfinder magnifier for nikon d3100

Hi all,
on my d3100 I use manual focus lens, and the way that I focus and it works for me, I find the object and then I defocus and then refocus and when it gets in focus I shoot the image. It seems to work for me most of the time. Now to get sharper I thought if my viewfinder was larger I could get the image sharper. If I could afford the nikon af-s lensl would not have to mess with manual focus, but for right now it will have to do.

Does anyone have any experiences with view finder magnifiers and what are your thoughts on this. Would appreciate any input on this
Kas

The SeaGull version you listed doesn't seem to get very good reviews.

I have a 7" LCD screen that fits in the shoe and plugs into the side of my D3100. That gets around the really annoying 30 second limit of liveview on the 3100. BUT it's really only of any use when using a tripod.

I only saw the seagull, does anybody else use something else, something that will enlarge the viewfinder size, hanging electronics really does not get it for me, as I do not use tripods, I am a walk and shoot kind of guy.
Kas

Post a link to the Seagull, will you, as I don't think I've ever seen such a device.