Anyone ever had this problem with their TLR?

2F/2F · Aug 8, 2008

Hello,

I borrowed a classmate's new C33 and 80mm lens to test it out for him and make sure all was Kosher. He and I now have twin cameras (purchased from the same place as well).

Everything seems to work mechanically. However, there is one huge problem with the camera: It is focusing the taking lens *behind* what appears in focus on the ground glass. Obviously the closer and the more wide open it is the worse it is.

My first thought was that the focusing screen is tweaked or incorrectly shimmed. It is, indeed, shimmed, with small brass washers on the rear and thin strips of black paper in front (looks OEM or at least professionally done). Mine has the same shims, however, and focuses fine.

The proper back for the film used is in place. We both have 120/220 models with both back doors.

Any thoughts?

Thanks in advance.

mgb74 · Aug 8, 2008

Is the mirror for the viewing lens properly in place?

glbeas · Aug 8, 2008

I've seen this happen with cameras that were dropped and the front standard was bent a little. Yoiu might also have a lens set thats been taken apart and reassembled wrong. Easiest way to check is to swap lenses and see if anything changes.

2F/2F · Aug 8, 2008

Thank you.

I thought the same, and I did check the mirror when I had the screen off. It looked OK, although I suppose it could have shifted in some way. I will double check.

MattKing · Aug 9, 2008

You should PM grahamp about this problem. I'm sure he can refer you to the right repair/maintenance resource.

I expect it is the shims.

Matt

Steve Smith · Aug 9, 2008

Also check the ground glass (plastic actually) is assembled correctly. I'm not 100% sure about the C33 but the C330 has a ground glass and a fresnel. the fresnel is below the ground glass and they are mounted with their ground/machined surfaces together.

Also note that with the bellows racked in completely, with the 80mm lens, the focus is past infinity. Infinity focus is with the bellows about 1/8" (3mm) out.

Steve.

Woolliscroft · Aug 9, 2008

I don't know the C33, does it have interchangable viewfinder screens like the C330? If so, you need to check that the screen is seated properly and that the mount is clean. Even a bit of dirt, or a paint flake can throw it slightly out.

David.

dpurdy · Aug 9, 2008

I would see if the problem is with just the one lens pair or does the problem still exist with another set of lenses in. I don't know about the Mamiya TLRs but with Rolleis the lenses can be set wrong or out of adjustment in comparison to each other.

wclavey · Aug 9, 2008

The c33 does not have interchangeable view screens (...at least mine doesn't) - - it is assembled very much like the c220 is, with the fresnel and the ground glass as described by Steve Smith. The Fresnel is actually glued to the ground glass in the corners and the position against the ground glass is very particular... I inserted a thin glassine sheet with a grid printed on it as a test and it threw the focus of when the aperature was wide. So make sure that it is tightly in place and not come loose due to dried glue - - I have seen that on some.

Added: Sorry, mine's a c3, not a c33 so strike the first sentence... the rest is still true

ic-racer · Aug 9, 2008

In my opinion, the biggest drawback of MF rollfilm is film bulge in the center of the frame. It always shifts the focus behind the intended focal point. A vacuum back or glass plate can help, but each has its own problems.

Steve Smith · Aug 9, 2008

wclavey said:
The c33 does not have interchangeable view screens (...at least mine doesn't) - - it is assembled very much like the c220 is, with the fresnel and the ground glass as described by Steve Smith. The Fresnel is actually glued to the ground glass in the corners

That's as I remember it. It is however, easy to take apart by an amateur 'repairman' so it may have been assembled wrong in the past.

Steve.

grahamp · Aug 9, 2008

Leave the screen alone on a C33 unless it needs attention and you enjoy resetting the spacers.

If you have two bodies, two lens pairs, and one lens pair does not focus correctly on either body, then that lens pair is out. The viewing lens is sometimes shimmed between the barrel and the lensboard for this adjustment. You actually adjust the focal length doing this as you alter the front and rear element spacing, but it is normally good enough. If the unwary try to unscrew the lens front cell they sometimes loosen the barrel instead, and the shims fall out. It does vary with the lens, but most have a retaining ring on the back that loosens with a lens wrench which is easiest to work on.

There is just a chance that the lensboard is bent, but it would not seat well. If the body tests well with another lens, I'd assume the body is square.

Anyone ever had this problem with their TLR?

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