Hey all, I shot with my new used field camera this weekend and as an experienced photographer friend of mine said, some funky things are going on with the focus. What should I do to verify that this is due to operator error (very likely) and not misalignment of the lens (also likely as it is about 30 years old)? In other words, are there test subjects to use? Is polaroid film okay for such tests? Jim Worthington

-- Jim Worthington (jcw@phr.ccmail.compuserve.com), August 12, 1998

Answers

I use 4x5 Polaroid film for a lot of things, but judging critical focus and sharpness is not one of them. At least not Polaroid prints. You might use type 55 for this application, I've never used it, but hear that the negatives are quite sharp.

A brick wall is a favorite test target, but you've got to be certain the the camera is very precisely aligned to that wall. Align the back parallel with the wall, and sharpness should be equal in all corners of the neg.

-- mike rosenlof (mike_rosenlof@yahoo.com), August 12, 1998.

Please define "funky".

-- Marv Thompson (mthompson@clinton.net), August 12, 1998.

Please explain "funky".

-- Marv Thompson (mthompson@clinton.net), August 12, 1998.

Here are a couple of things to check.

1. Are you sure that both the front and rear standards were locked before you put the film holder into the camera? The rear will likely move when you put in a film holder if it isn't locked.

2. Your concern about the age of the camera suggests that some components are loose. Is that true? Can you move either of the standards when they are locked?

3. Assuming that they lock tightly, you can verify that they are parallel when you want them to be so by using a good quality level. Use the level to position the camera base so that it is horizontal. Check that both standards are now vertical. Use the level to aim the camera vertically downward. Now verify that both standards are horizontal both left to right and top to bottom along the standards. If there is play in the system, it should show in this test. Doing these two tests will at least confirm that the standards are positioned where you would place them for a conventional image.

4. Does the camera have a fresnel lens or bright screen? If it isn't correctly installed, your plane of focus won't be coincident with the film plane. I believe that there's an article at the View Camera web site that explains this in detail.

5. I'd be inclined to use T-max for these tests. It's relatively inexpensive.

Good luck, Bruce

-- Bruce M. Herman (bherman@arctic.net), August 13, 1998.

Thanks for the good focusing advice. For your information, the old saying about looking for operator error rather than equipment error is true. I tested the lens by making sure that the back, the lens, and a brick wall were parallel. Then I carefully focused, processed, and had one really boring but well-focused picture. FYI also-- By "funky," I meant the presence of a strange diagonal plane of good focus in the midground with poor focus in the fore- and background. I think I made the beginner's mistake of using too many movements at once. Thanks again for all the help Jim Worthington

-- Jim Worthington (jcw@phr.ccmail.compuserve.com), August 13, 1998.