Where to focus with the loupe on Chamonix F2 ground glass?

[Times2]

Hi,

I bought a second loupe with the adjustable focus and now I'm wondering how to "calibrate" it. What on the ground glass should be in focus, thin diagonal lines or black guidelines/numbers or something else? Camera in question is Chamonix F2.

Thanks!:)

[BrianShaw]

The image, on the ground side of the ground glass.

[Kevin Crisp]

You want the grit of the gg to look sharp. Assuming you have a reasonably powerful loupe. If the grid is on the camera side of the gg that will probably work fine. Then when you get the eyepiece in the right position, tape it there.

[Doremus Scudder]

Note that if you have a Fresnel screen sandwiched together with your ground glass that there will be a lot of concentric circles on the viewing screen except for a center spot. You do NOT want to focus on the lines of the concentric circles; they are part of the Fresnel lens, which directs light better toward your eye, but not where the image you want to focus on is formed.

You DO want to focus on the frosted side of the ground glass. Often, you can take the lens off your camera and simply focus on the grain of the ground glass itself to find the proper focus for your loupe. If that doesn't work, find a detailed subject and focus on the image in the center spot (without the Fresnel lines), adjusting your loupe until the subject is as sharp as it will get.

Best,

Doremus