Questions about Ansco 5x7 ground glass

[brian steinberger]

I just purchased an ansco 5x7, I cannot seem to get a sharp image on the GG. I even tried focussing my loupe at different distances and nothing worked. I had a Wista 4x5 in the past and the GG and fresnel was crisp and sharp. If the GG on my ansco is original could it just be not up to par with modern GG with a fresnel?

If I should replace the GG what are your recommendations?

Btw.. I'm using a Rodenstock 180/5.6 and a Rodenstock 4x loupe.

 

[pdeeh]

is it round the right way?

 

[shutterfinger]

1. Remove the ground glass from the camera.
2. wash both sides in warm water and dish detergent using only your finger tips and a gentle tough to rub the surfaces thoroughly.
3. rinse thoroughly.
4. rinse in a weak photoflow solution.
5. stand on end or corner in a safe place and allow to air dry or dry with a clean lint free towel.
6. reinstall in the camera ground side toward the front standard/lens and check image quality.
If the image quality is acceptable
1. remove the back from the camera.
2. using a straight edge rigid enough not to bow lay it across the back making sure it is not on a raised portion higher on one side.
3. measure from the straight edge to the ground glass surface at several points on the film, top to bottom/left to right. I usually use a 3/3 grid and measure at the center of each box. All measurements should be the same.
4. insert a film holder with piece of scrap film you normally use toward the camera side, remove the darkslide from the camera side.
5. repeat the measurements, they should match the measurement to the film surface.
6. add or remove shims to/from the ground glass mounting to the frame as needed to get the measurements to match.

 

[Jim Jones]

It sounds like a lens problem to me; perhaps a misplaced or missing element.

 

[brian steinberger]

It sounds like a lens problem to me; perhaps a misplaced or missing element.

Jim, this is what I fear. How do I know if I can fix this problem or I should just return the lens?

 

[brian steinberger]

Here's a shot of the lens:

 

[John Koehrer]

Try this:
Mount the lens and measure from the GG to the front standard. Close is good enough.
Adjust focus until it seems sharp, then loosen the front element and while looking at the
GG see if there's any change in the focus. Improvement or no? Improvement suggests a missing shim.

Getting worse? Ahhh nuts! Back it goes.

 

[Ian Grant]

If your Agfa Ansco still has it's original screen then it'll be quite coarse and harder to use than a modern plain screen, or screen & fresnel. I have 2 10x8 Agfa Ansco's which came with their original screens and with a new screen can now focus a 151mm f16 Ross WA (Protar).

Have you used the lens before, if not you need to try the lens on a different camera to try and eliminate if it's the lens itself. While it looks ok it's not (as it should) unknown for sellers to put the wrong rear elements on a lens.

Ian

 

[brian steinberger]

Ian, that's kind of what I was thinking about the GG. however, how do you explain the lens not producing an infinity image at 180mm?? That's what leads me to believe the lens is faulty.