Help --- focus problem

[northcarolinajack]

I just finished restoring an old 8x10 Empire State camera. I had an old 4x5 back so I decided to make a reducing back for the 8x10. After I finished, as always, I shot from my open garage door the house across the street to check for leaks or other problems. The shot is attached. The focus on the ground glass seems spot on, but the film focus is soft. I used ¼ inch plywood and added the back. What did I miss with the construction? I would love to have an answer to solve the problem.
Hope someone know the answer.

Jack

[mdarnton]

The problem wouldn't be with your part of it.

In this case, assuming you can focus, for whatever reason the ground glass not close enough to the lens relative to the film. That's not a problem with your construction, since the problem is behind the surface against which the film holder and ground glass frame rest. That is, it's either a holder error or ground glass placement.

The first place I would look is for something under the ground glass in its frame shimming the GG backwards from where it belongs: shims that shouldn't be there, or a fresnel. Either would force you to pull the lens back farther than it should be, making the focus shift from the house to the trees behind.

[IanG]

Assuming the back itself wasn't modified it's possible it should have a fresnel. Pacemaker Graphic backs came with or without a fresnel the casting number is the same but the pillars supporting the screen are different when a fresnel was added by Graflex (from new). If the fresnel has been removed then the glass isn't the correct position so it's not the same register as the film plane.

Ian

[mdarnton]

Assuming the back itself wasn't modified it's possible it should have a fresnel. Pacemaker Graphic backs came with or without a fresnel the casting number is the same but the pillars supporting the screen are different when a fresnel was added by Graflex (from new). If the fresnel has been removed then the glass isn't the correct position so it's not the same register as the film plane.

Ian


In this case, adding a fresnel would make the focus go in the other, wrong, direction, back-focusing even more. Perhaps, then, someone added one where it wasn't supposed to go.

[IanG]

In this case, adding a fresnel would make the focus go in the other, wrong, direction, back-focusing even more. Perhaps, then, someone added one where it wasn't supposed to go.

If you add a fresnel to a Pacemaker focus frame that's not designed to use one then it has to be added to the outside of the focus screen, and the hood won't attach properly unless you shim the two retaining fittings that hold the glass & fresnel in place. It#s more likely to be the other way around a missing fresnel.

Ian

[mdarnton]

If you add a fresnel to a Pacemaker focus frame that's not designed to use one then it has to be added to the outside of the focus screen, and the hood won't attach properly unless you shim the two retaining fittings that hold the glass & fresnel in place. It#s more likely to be the other way around a missing fresnel.

Ian

If it's missing one and should have one, you'd see the opposite phenomenon from that in the OP's photo--the foreground would be in focus, not the trees behind the house or the back of the roof; adding a fresnel where not needed would cause back-focusing, not cure it.

[IanG]

We can't read that much into the OP's image.

There's another issue as the right side is sharper than the left so maybe the back shifted when the darkslide (film holder) was inserted.

Ian

[djdister]

We can't read that much into the OP's image.

There's another issue as the right side is sharper than the left so maybe the back shifted when the darkslide (film holder) was inserted.

Ian

Right. It's not a focusing problem, it's more a problem of parallelism of the camera. The decrease in focus sharpness from right to left (of a relatively flat surface across the street) suggests that the front and rear planes are not parallel. Some attention needs to be paid to the structure and fit of the manufactured reducing back.

[mdarnton]

OP? What are you seeing? Specify the problem, please, since we're obviously having a disagreement about what the problem is, or even whether an image showing the problem is relevant!!???

[northcarolinajack]

Moved back film holder 1/4 inch all with scrap wood and gaf tape. Sure all items were level and parallel. Had light leaks so cropped.

Jack