What magnifier to check focus on ground glass?

[Rogier]

Hi,

I have hacked 2 Holga Camera's and need to calibrate the focus. For the Angulon lenses I have put on them.
I have used ground glass and a loupe normally used to view slides and negatives. Is this the correct magnifier to use?
Or do I need to get a loupe that is used by larger format photographers?

 

[jmcd]

Magnifiers for large format are typically around 4x. Better magnifiers are sharp across the view.

 

[Messsucherkamera]

I would think that any slide viewing loupe that has quality glass and has enough magnifying power - 6x or higher, perhaps - would work well.

 

[citizen99]

I use a loupe bought from a local optician which I see is marked 7x, which is about the maximum strength allowing me to get my face/nose close enough to the camera 😉.

 

[Rogier]

Thanks for the quick advice. I have to recalibrate the helicoid. Since my last roll was almost all out of focus. Wanted to make sure that I was not missing something.

 

[mervynyan]

4x is good enough for groundglass, anything more just views the spots on the ground glass.

 

[citizen99]

4x is good enough for groundglass, anything more just views the spots on the ground glass.

I actually use 3M 'Magic Tape' stretched tautly across the film plane, I find that that presents the image clearly enough to benefit from the magnification that I use. (I use up to 6x9, I suppose it would be less critical at larger formats at 'standard' focal lengths.)

 

[Rogier]

I just went outside with my Franken Holga.
8X Agfa slide viewing loupe covered with black gaffers tape (love that stuff!) and covered the entire ground glass in order to fix the loupe to the ground glass and the glass to the Holga. On the front side is a 12-17mm Helicoid with a 1/4" extension ring and a Linhof Angulon 65mm lens.
The rangefinder is a "JB" recently bought inexpensive via eb.
Ended up putting 6 marks on the barrel of the Helicoid that correspond to the marks I made on the Rangefinder dial. Closest focussing distance 4+ feet...


IMG_4460 by Rogier Diver, on Flickr


IMG_4459 by Rogier Diver, on Flickr


IMG_4456 by Rogier Diver, on Flickr