frosted glass vs film plane difference.

[Grandpa Ron]

I am hoping this is the correct forum for this issue.

I restored a Seneca 4x5 view camera with a date stamp of 1909. Over the last year or so I have been using it mostly as a pin hole camera. However, when i use it with my 127 mm or 163 mm lens the images just did not seem quite as sharp as they should be.

Let's suffice to say it has been a steep learning curve. But among the many articles I have read was the suggestion to check the distance from the lens board to the film and glass planes.

A a quick check with ruler indicated the film was about 1/8" farther back than the frosted glass. Careful measurements with digital calipers shows the film plane of the film holder is .138" (3.5 mm) farther back than the distance to the frosted glass. The film thickness is .007" (.178 mm). I check a few of my film holders and the distance is consistent.

My solution is to slide a .130" (3.30 mm) thick square frame into the film holder slot to move the frosted glass back to the film plane. This seems like a crude but effective solution but I was wondering how other folks have solved this problem.

[maltfalc]

how thick is your glass and is the frosted side facing you or the lens?

[Oslolens]

Shim the glass in to correct position, but first make sure the frosted glass side is towards the lens.

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[LabRat]

And once you do that, do a film focus test by setting up 3 playing cards an inch closer and further from the center card and focus camera on the middle card... Shoot a piece of film focused on the middle card and see what looks sharpest on the developed film... Use a wider aperture when shooting...

Steve K

[Tin Can]

I have used a shim and attached it to the gg frame permanently

I had some tape that worked very well

[Grandpa Ron]

Yes I did check and the frosted glass is inside the camera. I will o the playing card test.

I guess I should not have been surprised that a 112 year old camera was not built to modern specs.

Thanks for the info.

[maltfalc]

Yes I did check and the frosted glass is inside the camera.

so frosted side inside facing the lens? is the glass 1/8" thick and can it be removed and flipped around?

[Ron (Netherlands)]

A a quick check with ruler indicated the film was about 1/8" farther back than the frosted glass. Careful measurements with digital calipers shows the film plane of the film holder is .138" (3.5 mm) farther back than the distance to the frosted glass. The film thickness is .007" (.178 mm). I check a few of my film holders and the distance is consistent.

How is your film attached to the plate holder? In the old days they used glass plates with a film layer: the glass plates were as thick as the ground glass screen (i.e. the frosted glass). If you use so-called flat-film aka sheet film, you have to compensate for the loss of the glass layer. Already in the old days this was done by inserting metal film sheats, some however made them from plywood, others use glass to attach the sheet film to.