I use a Peak 10x focussing loupe. With any loupe, it's important to be certain it's focussed on the texture of the groundglass. Do this by removing the lens and pointing the canera so the GG is illuminated, focus the loupe so the texture is clearly seen and either lock or tape the loupe at that setting.
Originally Posted by Doc W
The trouble with reading glasses is that you cannot do this - do you really want to go to the trouble and expense of 8x10 (or any other format) and do half a job of focussing?
I stated what I use, this works very well for me, my eyes, and my way of working. It may not work well at all for you. It's probably best to try as many different types and powers as you can.