Tilt of the front standard under the weight of the lens

[Tintinla]

Hi:

I own both a Cambo 45SF and a Cambo 45NX. I also own and use a Zig Align for parallelism of the standards.

I recently made the following experiment: I align either of these cameras properly with the Zig Align, meaning one can see through the hole in the front standard mirror an infinity of circles perfectly aligned on the mirror sitting in the rear standard. The controls are tightened properly so that they keep this corrected position.

I now attach a metal wire around the lens to be used and fix the wire at two places on the front standard still set with the Zig Align. Since I use a Linhof to Cambo adapter as the front standard, these 2 places are the 2 metal "pieces" on which the lens rests. I let the lens hang freely from the wire and look again in the hole of the Zig Align. The weight of the lens invariably tilts the front standard forward, enough to throw off the alignment in that direction alone. Removing the lens reverses the process and the camera is realigned. This happens on both Cambos.

As said, the controls are pretty well tightened and tightening them more could endanger them. The NX is more sturdty than the SF and exhibits the exact same fluctuations of forward tilt. The NX has axial tilts and the SF base tilts.

As anyone gone through the same procedure on their cameras and Zig Align. We are talking here of a substantial tilt (substantial in the sense that if it were there to start with, you would definitely correct for it, at least for the ones who have come to trust their Zig Align).

Second, if you do have checked your alignment with the lens weighting on the standard, and have found the camera to remained aligned, could you mention the brand and model. I am considering the purchase of a Technika 2000 and of course would love to know if such a test had been run on that camera.

I live in the Los Angeles area and am available for carrying such a test if your camera mounts the Technika lensboard. The mirror that sits in the front standard for my Zig Align is installed in a Technika lensboard and is not removeable from there.

Thanks for your collaboration.

[Alan Davenport]

[just made a sidetrip to the website of the product in question. interesting, but not applicable.]

I use a small torpedo level to set the camera to level (enough) and to make the rear standard vertical (enough.) I've always found the normal detents and markings on the cameras close enough to set the front standard, since it's seldom that I don't use any tilts or swings.

I'm wondering what kind of photography you do, that requires the standards to be this closely parallel? Parallelism is a nice, theoretical starting point for the two standards on a large format camera, but unless you're shooting a flat piece of paper that is also parallel to the standards, it is only a starting point and not where you'll be when you release the shutter. If you're not using movements, maybe you should try a different type of camera that won't flex.

I'm sure there are applications that require this kind of hair-splitting precision. LF photography in the real world isn't usually one of them. This alignment thing sounds like another solution in search of a problem. Put it in the drawer and go take some pictures.

Whoa, hey, I just noticed that you only joined today. You're not here trying to plug your company's product, are you?

[Brian Ellis]

Thanks for posting this information. I'm always happy to learn from people who seem to enjoy testing because I hate testing myself. But I have to say that keeping the standards perfectly positioned to the degree you're talking about here seems a little overboard, at least for the kind of photography I do. I suspect that all the various things in LF equipment that can be off by a few micromilimeters either all balance each other out or, if they don't, it doesn't matter.

[Tintinla]

Hi:

No I am not trying to plug any product here. I don't sell any product either. I am just a photographer.

It is interesting to note that the kind of parallelism I am talking about is an absolute given in a Hasselblad, Mamiya and the like (and there must be some reason to that). Contax went as far as creating a vacuum back so that the film would be perfectly flat both on 35mm and 645. It is also known that some BetterLight scan back users are using a Zig Align and I am quite sure would not tolerate the kind of error I am seeing. I believe that this is a matter of how big you enlarge.

In any event, I plan to enlarge very big and I believe that at the degree of magnification I envisage, this kind of error will be visible, in particular on prints derived from wide angle shots. The problem I have mentioned is apparent with a Nikon 90mm F5,6 SW among other lenses.

[Tintinla]

Hi:

Sorry, I forgot to thank you both for your input. So, thank you. I much appreciate.

[Ed Richards]

Since front tilt only moves the plane of focus, I am not sure why it matters if the front standard sags a little - you are going to use swings and tilts to move the plane of focus anyway, and you can see what you are doing with a magnifier. Makes a big difference in an enlarger because everything is flat, but not in a view camera. Even in the flat paper example, you would just correct for sag as part of focusing.

[Tintinla]

Yes, I know what you are saying and probably have corrected for this in the past not knowing about it. It just would seem more natural to start with a definite zero position and then make adjustments.

Also, let's say the adjustment you require is now a front swing instead of a tilt. Can one still Scheimpflug if the plane of focus is tilted and swung at the same time?

It occurs to me that I have never enlarged bigger than 16 x 20 and my plan is to go quite a bit above that.

In any event, I was trying to see if some users had found either the same issue or found that their camera maintained good parallelism irrespective of the weight of the lens.

Thanks.

[Oren Grad]

The Zig-Align promotional material focuses its discussion on specific situations where lack of parallelism is most likely to cause problems: in enlarging and in copy photography.

Have you actually encountered any situation in which there was a sharpness problem that you attributed to a lack of parallelism in the camera? If so, under what conditions (subject, focus distance, focal length, aperture, etc.)?

[Ed Richards]

> Yes, I know what you are saying and probably have corrected for this in the past not knowing about it. It just would seem more natural to start with a definite zero position and then make adjustments.

Sure, if there were no costs involved. But to get a perfectly parallel system when loaded with a big lens one would have to use a heavy studio camera which would be very difficult to use in the field. I suspect a Sinar P2 does not sag much, but I would hate to tote one around. You have to look at the degree of sag you are dealing with - Zig-align is designed to detect problems that are well below the threshold of visbility in real photography - it does not affect sharpness because you are shooting three-D subjects. It only slightly shifts what is sharp, which is going to be impossible to see. In contrast, an enlarger is mapping one flat sheet to another, and even the slightest tilt puts most of the image out of focus.

[Leonard Evens]

In the real world, exact parallelism of the lens plane and film plane are impossible. If nothing else, the film won't lie perfectly flat no matter what you do. So it is always a matter of keeping the lack of parallelism within acceptable bounds. But what is acceptable will depend on the situation.

Shorter focal length lenses will yield more of a shift in the plane of exact focus. To some extent, when focused at the same distance, such lenses will compensate with greater depth of field at the same f-stop. On the other hand, it is harder to check focus at the edges of the field with such lenses. I've found at times that I ended up slightly out of focus at the edges when photographing a building facade with a wide angle lens, so in such situations, I try to be careful to maintain parallelism of the standards.

In many siatuions, just using the detent or zeroed positions is adequate for all practical purposes. In cases where parallelism may be critical, I think it is best to check it with the lens in place. Use of a levels should be adequate for the degree of accuracy required in large format photography, so I don't think more elaborate methods are called for. Check of tilt is best done with the camera level because that is when the lens weight will be relevant. Check of swing can be done with the tripod pointing down and the gg level. A torpedo level placed across the lens barrel can then be used to check allignment. Horizontal adjustment shouldn't be affected if the camera is returned to level.

Finally, checking on the gg glass will confirm that all is well. For example, when photographing a building facade which is plumb, you want the back vertical and parallel to the facade. The former is checked with a level and the latter can be checked by making measurments of the image on the gg. Distances which are equal in the subject plane should yield equal gg images. Then a check of focus across the field will confirm that all is well. If not, one can make small adjustments of tilt or swing as necessary. Some people prefer to do it entirely that way without worrying to start whether or not the standards are parallel. But I find that once I identify when the standards are parallel, I can leave them set that way for most of my pictures and then I don't have to make any adjustments afterwards. Overall, that saves me time.