clipping corners on a ground glass

[shutterfinger]

What angle and distance from the corner should a ground glass be be cut for clipped corners?
I prefer the industry standard if one exists.

Thanks in advance.

 

[AgX]

The angle should be 90° to the radius to to the opticakl axis, thus tangential.
The distance from the corner should be so long that the gained opening yields easy viewing at the lens.
(Not very helpful? Well, you always can make the opening larger...)

 

[ic-racer]

Mine are all cut by the respective camera manufacturers so the remnant formed an isosceles triangle.

What AGX wrote is functionally correct for the cutout's use of viewing the aperture.

 

[tedr1]

I don't know of standards, possibly Kodak had a standard and I'm sure the Swiss also did but how to find out the details? With most formats and do-it-yourself it is probably easier to achieve a 45 degree angle and simply make all four opening the same size, perhaps 0.5in?

 

[mdarnton]

I suspect it matters what you're trying to accomplish. To let out air? The minimum. To see the aperture to determine cut-off? Slightly more. On my Ansco views the rebate is cut with a table saw, so it ramps up at the corners; on those, you need to cut off enough so the glass rests on the flats rather than the ramps, and that's quite a bit more than the first two cases require.

 

[shutterfinger]

I have in for repair a Gandolfi full plate with a 4x5 reducing back whose ground glass needs clipping. There is no lens at present.

 

[ced]

Just measured an old Linhof 4x5 and the length of the cut is 25mm giving an opening of 8 - 10mm depending on where the glass fits into the rebate...

 

[AgX]

lWell, you always can make the opening larger...)

Just make a cardboard substitute for the ground glass and test different opening sizes for those situations you would want to look directly to the lens.
Then use the size of best suited opening for the clipping of the ground glass.

 

[DREW WILEY]

There is no industry standard, just examples. It depends on how wide your angle of view is. Cut too much and it interferes with composition, too little
and you won't be able to see the iris.

 

[summicron1]

There is no industry standard, just examples. It depends on how wide your angle of view is. Cut too much and it interferes with composition, too little
and you won't be able to see the iris.

Maybe I'm just dim, but why do you need to see the iris? Why clip the corners at all?

My Speed Graphic's glass is not clipped, my B&J's is. I see no advantage, but i am happy to admit to gaps in my education.

ct

 

[shutterfinger]

Clipped corners serve two purposes 1. on cameras larger than 4x5 closing the camera the bellows from focused distance compresses air in the bellows. Clipped corners allow the air to escape. On a tight fitting camera the bellows may even collapse when extending the bellows during focusing without clipped corners. 2. factory clipped corners allows one to look through the clipped open at the rear of the lens. if you can see the aperture then the lens will not vignette, if you cannot see the full aperture at exposure setting then the lens will vignette. This is most useful if using movements.