Loupe for calibrating critical infinity focus on ground glass..10x or 20x?

brainmonster · Jul 13, 2020

I plan on buying a belomo triplet/quadruplet loupe as I've heard they are a good price for performance.

Most people seem to recommend 10x for general use, but I had someone tell me 20x is needed for judging critical focus. Do I need to get 20x for calibrating infinity focus on ground glass on film plane? I've heard that 20x vibrates a lot with hand shake and you need to be careful, will this be a big issue.

Dennis-B · Jul 14, 2020

Absent other information, I'm assuming you need this for ground glass focusing on a view camera. If so, the Belomo loupes appear to be useful for jewelry applications. 10x is a lot of magnification, even for critical focusing. I've always used 4x-8x for this task. I've also wound a couple of turns of black tape around the bottom, to darken the loupe from extraneous light.

Mileage and preferences vary.

Dan Fromm · Jul 14, 2020

OP, I can't quite understand what you want to accomplish. Please explain.

ColdEye · Jul 14, 2020

I like 4x loupes for this. But thats just me.

randyB · Jul 14, 2020

For decades I used the lowly Agfa 8x loupe, it was adequate, but as time has screwed with my vision I have switched to a 10x lithographers loupe which was very good but the field of view is very small and I have to have my face very close to the GG which to me is a pain. I am looking at the Toyo/Omega/I can't think of the name GG loupes that have extended eye relief that are about 4-7x.

brainmonster · Jul 14, 2020

I think I'm going to get the belomo 15x loupe.

I am trying to callibrate infinity focus on a vitomatic II. I took off the lens to clean it but I couldn't figure out how to mark the infinity focus. The rangefinder is also decoupled so I need to use the film plane to mount the lens ring correctly for infinity focus.

I'm not sure if the belomo loupe needs to be held some small distance away from the film plane or not. Perhaps it's better to use a 10x or so loupe with a bracket that can be taped to the ground glass. Maybe I'll just order both and see which one works.

shutterfinger · Jul 14, 2020

When using high magnification on a ground glass or view screen the grain of the ground glass or view screen can interfere with seeing the image on it. I use a Horizon 8x focusable loupe and can get critically sharp with it.

Deleted member 88956 · Jul 14, 2020

brainmonster said:
I think I'm going to get the belomo 15x loupe.

I am trying to callibrate infinity focus on a vitomatic II. I took off the lens to clean it but I couldn't figure out how to mark the infinity focus. The rangefinder is also decoupled so I need to use the film plane to mount the lens ring correctly for infinity focus.

I'm not sure if the belomo loupe needs to be held some small distance away from the film plane or not. Perhaps it's better to use a 10x or so loupe with a bracket that can be taped to the ground glass. Maybe I'll just order both and see which one works.

Isn't it going to cost at least same or more than another Vitomatic II? You could use second as example for how to fix first, then sell one back. Just saying.

BrianShaw · Jul 15, 2020

IMO, a wee bit of DoF beats the hassle of using a magnifier greater than 4 or 6X.

Loupe for calibrating critical infinity focus on ground glass..10x or 20x?

Deleted member 88956

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