First-time visitor here, so I thought I would put out a problem that has been bugging me for a long time now. Sorry it is so lengthy, but a full picture of what I have gone through seems necessary . . .

I shoot architecture and interiors in Sweden, and shortly after I purchased a new 4x5 Cambo 45 SF about 7 years ago I ran some tests to get a handle on what my actual depth of fields would be when focused at different distances and with various apertures. To do this I set up a series of objects at 1 meter intervals, and took a series of photographs with the focus on different objects at several of the different distances. Each object I focused on was shot at several apertures, ranging from f/5.6 to f/45. I performed this test with 2 lenses, a Schneider 58mm XL and Schneider 72mm XL. Since I work a lot with a 6x9 back, the 58mm and 72mm are essential wide angle lenses for me, so I wanted to be confident about what to expect as different conditions and needs arise.

When I looked at the results of the tests, however, I was shocked to see that in all cases the object I focused on was not in focus at all on the film. And I mean it was often way off, not just a little bit. So for example when an object 12 meters in front of the lens was sharp on the ground glass, what showed sharp on the film with the aperture at f/5.6 was an object located 4 meters in front of the lens. 8 meters off! When focused on an object 6 meters in front of the lens, the only thing sharp on film when shot at f/5.6 was an object 4 meters in front – 2 meters off. Thinking I must have made some careless errors, I ran the test again. Same exact results. All tests were made with a good 4x loupe, using well-lit objects having good details (like texts, plants, etc.), with both the front and rear standards carefully levelled (no tilts, no swings) and all knobs securely tightened.

I went to the dealer who sold me the camera. He checked to see if the plane of the ground glass coincided exactly with the plane of the film in the holder when inserted in the camera. It did. We did the same test together in his store, where we both were in agreement about what was in focus on the ground glass. We tested a Cambo 6x9 back, a Linhof 6x9 back and some 4x5 sheets in Fidelity holders. Same results in all cases, though the 4x5 sheets were off to a slightly lesser degree. The dealer contacted Cambo in Holland, who requested that we send the camera and a sheet of test negs to their factory. A week after they received it they wrote back saying that they saw nothing wrong (!), but sent a new camera to me anyway (I guess to make me feel better). I tested it too. Same results.

Well, since I am nearly always shooting at f/22, I get by anyway with good sharp images, where I focus a little beyond the point where I otherwise would have if this problem didn’t exist. But it is really unmanageable when I need to open the aperture to reduce depth of field, or when for example there are people in a space who need to be sharp, which under lower lighting conditions requires faster shutter speeds.

I was prepared to agree with those who told me that Cambo is just an inferior product, until another dealer about a year later informed me he got in a used Arca-Swiss F-Line in good condition, which I could get for an affordable price. I told him about my focusing problems with my Cambo, so together we performed the same test in his store with my lenses mounted on the Arca. And guess what? Same results again!

Needless to say, I never did discover anything about depth of field. . . .

Can anyone enlighten me about what might be happening? I know wide angle lenses are supposed to be “difficult to focus,” but this is a bit extreme, isn’t it?

Thanks,

Michael Perlmutter



PS: I know all the literature says one should shoot 4x5 at f/22, that smaller apertures cause problems that degrade the image, but I must say that in my tests I saw no apparent degradation in the shots taken at f/32 and f/45. Just a much wider depth of field! Comments?