Ground glass glasses

Alan Edward Klein · Aug 7, 2020

I'm new to large format. I have a Chamonix 45H-1 4x5. The fresnel I believe is between the GG and my eye. How do you differentiate that you're focusing on the ground side of the GG and not the wrong side of the GG focusing on the fresnel?

Bob S · Aug 7, 2020

Alan Edward Klein said:
I'm new to large format. I have a Chamonix 45H-1 4x5. The fresnel I believe is between the GG and my eye. How do you differentiate that you're focusing on the ground side of the GG and not the wrong side of the GG focusing on the fresnel?

You point the camera at a light source, take off the lens, put the loupe on the fresnel and focus the loupe till the grain of the gg is sharp. Your loupe is then focused on the film plane.

Neil Poulsen · Aug 8, 2020

I purchased two pairs of drugstore reading glasses: one for the right eye and one for the left eye. Then, I swapped the two right lenses in the glasses purchased for the left eye. Works fine, and both eyes are corrected.

I like these for composing the image under the dark-cloth. I use a 7x loop to fine tune the focus.

138S · Aug 8, 2020

Alan Edward Klein said:
I'm new to large format. I have a Chamonix 45H-1 4x5. The fresnel I believe is between the GG and my eye. How do you differentiate that you're focusing on the ground side of the GG and not the wrong side of the GG focusing on the fresnel?

What Bob said, on any doubt about how the GG grain looks, just (at home) explore the inner side of the GG with the loupe.

Nokton48 · Aug 8, 2020

The glass has a grain pattern which should appear razor sharp and magnified for fine focusing. And on that exact plane you should focus the camera.

I use a number of hand held 7X-10X loupes, and I have a PEAK 30X pocket magnifier I bought from Edmund Scientific which I have always found useful.

The most hands-free one (other than magnifying eyeglasses) is the more modern Binocular Sinar Viewer. It has an elastic head strap to keep it where it needs to be attached to your face.

Doremus Scudder · Aug 8, 2020

An observation on focusing with a loupe:

Yes, it is really important to focus your loupe on the grain of the ground glass, where the image is projected and where the film plane is.

However, if you don't, the sharpest image you can get with your loupe, even if it's slightly out of focus, is still going to be the place where the image is focused most sharply on the film. So, even if you're holding the loupe free, like I do, or if you've not set the focus on your skirted loupe exactly correctly, you are not likely to make a focusing error if you find the sharpest image you can and set focus there.

Also, when holding the loupe/magnifier free, like I do, it's not at all difficult to adjust the distance between loupe and ground glass to find the ground surface to focus on once you know what it looks like. A bit of practicing with a free magnifier and the skill becomes second nature.

Best,

Doremus

grahamp · Aug 10, 2020

I also favor flip-up magnifying lenses over my regular prescription glasses for anything short of critical focus with a good magnifier. I have astigmatism, so I need either a custom prescription set (I already have readers, computer, and sunglasses - I don't need another set), or these to see. I don't like removing my regular prescription because I like to look around when I am out from under the dark cloth. I do need to switch to a loupe for final focus checks.

I used to use the flip-ups for doing network wiring at work, and they are handy for all sorts of jobs.

Darryl Roberts · Aug 11, 2020

Doremus Scudder said:
Magnifying glasses are great for general viewing of the ground glass, but I'd recommend a loupe for fine focusing as well.

Get the right diopter reading glasses that enable you to focus on the ground glass (or anything else, for that matter) at a comfortable distance. Too weak and you'll be too far away from the gg; too strong and you'll be too close. If you wear glasses that correct for astigmatism, reading glasses may not be ideal. I use clip on magnifying glasses over my regular glasses (I like 3+ diopters, BYMMV). Mine come from Cabelas and are intended for fly fisherman with bad eyes; just flip them down and you can see to tie that fly on to your leader; flip them up and you have your normal, corrected vision.

In addition to the magnifying glasses, you should use a loupe for the fine focus. I like 6-8X loupes, like Drew. However, contrary to many, I use a free-floating loupe, really just a small 6x magnifying glass, that doesn't touch the ground glass. Yes, I have to move around to make sure I'm focused on the ground side of the ground glass and not on the Fresnel lines, but I don't find that difficult. The upside is that I can change the angle of the loupe to the ground glass to be able to see into the corners and find the sweet spot when I'm using lots of movements; things a fixed-length skirted loupe can't do.

Note: you don't have to remove your glasses or your readers/magnifying glasses when using the loupe as long as you can adjust it to focus sharply with them on (a non-issue with a floating loupe; you just move it closer to/farther from your eye).

Hope this helps,

Doremus

Thank you

Andrew O'Neill · Aug 11, 2020

I found a pair of +4 specs at the dollar store. Work really well. I look like Bubbles from Trailer Park Boys!

Ai Print · Aug 12, 2020

I use a combo of a 4x and 10X loupe for focus and -3 reading glasses for final inspection of composition. I have been able to nail focus with just the glasses using the Maxwell screen in my 45N2.

Ground glass glasses

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