Bellows Length - ??

[Bruce McCrory]

Help! I jumped into the quicksand of LF. "Too short, too long?"

First: How do you determine needed (desired) bellows length for a field/rail, or lens? Maybe, the question is what is the relationship of lens-to-bellows-to-image circle.

Now, to make it simple. Should I get the longest extension I can afford, or is something else more critical to choice?

Thanks, Thoroughly confuse...hbm

[Nick_3536]

What matters are the lenses you want to use and how you want to use them. You need at least enough bellows to focus the lens at infinity. This is usually a distance equal to the focal length of the lens. If you want to focus closer you need more. Obviously you usually want to focus a little closer then infinity so tack on say 20-30%. If you want to do 1:1 closeups you need 2x the focal lenght in bellows. Now before you go out and get the longest bellows you can find the flip side needs to be looked at. Short lenses might not work great on a camera with a lot of bellows. So are you a long lens person? A short one? Or a bit of both? What do you intend to photograph?

[Michael S. Briggs]

The main factors in determining what bellows length you need are the focal lengths of the lenses that you will use with the camera, and how close you want to focus with each lens. For most photographers, the bellows length will be determined by the longest focal length lens that they will use. In some cases it might be determined by a shorter focal length if you want to do macro work with that shorter lens.





There are simple equations which relate the lens focal length and distance to the subject to the required bellows extension. The longer the focal length and the closer the subject, the more bellows extension is needed. The equations are given and explained in David Jacobson's Lens Tutorial (http://www.photo.net/learn/optics/lensTutorial). For example, if you want to focus a f=250 mm lens on a subject So=1000 mm away, the extension needed is Si=316 mm. (Be sure to use the same units for all quantitites.) The magnification will be 0.32, i.e., the image on the film will be one third life size. Some of the small field cameras only have 300 mm of extension and so wouldn't be able to focus a 240 mm lens this close.





So think about what lenses you might use, and how close you might focus, and you can calculate what bellows extension your camera should have.





There is an exra step in the calculations if you plan to use a true telephoto lens.
Unlike 35 mm photography, most long LF lenses are not telephotos -- a true telephoto lens needs less bellows extension than would normally be needed for its focal length. You can search the archives about this, or others may chime in....

[Leonard Evens]

Clearly the bellows has to open up enough so that you can move the lens and film as far apart as the rail or bed will allow.

But you probably mean that distance, the maximum bellows extension possible on the bed or rail. Clearly one would like that as large as possible to allow the use of very long lenses. But that puts physical demands on camera design, and it is seldom possible to do that except in a large monorail camera designed to be used in a studio. Cameras, of any design, meant to be used in the field, will typically have a somewhat limited possible total extension, usually less than 400 mm. For example, my Toho FC-45X has a maximal total extension of 360 mm. My longest lens is a 300 mm lens. If I want a longer focal length lens and I hope to be able to focus closer than infinity, I will have to get one of telephoto design, which allows the lens to be closer to the film plane than its focal length, often significantly closer. The Toho has a monorail design where the rail closes down for compactness. There is a limit to how far they can let it open up and still maintain rigidity. Field cameras, where the camera folds up into a box, are necessarily also going to be somewhat limited in total extension.

So, as in most things, it is a matter of balancing several different factors against one another. Maximal bellows extension is just one factor. By itself, it shouldn't determine what you get.

[Alan Davenport]

As a real-world example, I present my situation: a Calumet Wood Field 4x5 (relabled Tachihara) and a 254mm lens. The closest I can focus that lens is about 5 feet. Not a problem for me as I shoot mainly landscapes, and if I need to shoot closer I have a 150mm that can get to lifesize. If you need longer lenses, there are telephotos available which need less bellows extension than the focal length would indicate.

[Ken Lee]

Some cameras (Arca-Swiss, Sinar, etc) allow you to add extension rails ad infinitum. Many cameras allow you to replace the standard bellows with longer or shorter versions, appropriate for very long or very short lenses. With these more modular designs, you are less restricted by lens length, as long as you are willing to purchase the additional components.

[Brian Ellis]

The rule of thumb I've seen is that your bellows should be about 25% longer than your longest normal (i.e. non-telephoto) lens. That should be sufficient for most general purpose photographic situations. If you want to do macro photography (i.e. make photographs where the object being photographed is the same size on the film as it is in real life) you need a bellows twice as long as the lens with which you'll be doing that kind of photography (e.g. a 150mm lens needs to extend to 300mm to make a 1-1 image). There is a mathematical formula I've seen posted here for determining how close you can focus with a particular film size and lenses of any given focal length, perhaps you could find it in the archives.

[Bruce McCrory]

I really appreciate everyone's help. Sorry I made the question so generic - I'm at the first rung of the LF ladder, trying to select a field camera that won't limit from the get-go. Aiming toward 5x7/4x5 reduction, which probably will cause exponential confusion.

Am sure that the first subjects will be "pretty outdoor views". However, I would like to do close subjects... bushes, flowers, leaves (my profession). This forum has so much that one can easily get lost, and I may have cruised through Jacobson's formula -- I do know there is a lens/extension relationship. However, the "adaptation" of lenses to various uses (?) such as tele, normal, even enlarging, can turn mystifying quickly. Some of the responses allude to this variability. I'm also guessing that due to bellows extension the same lens can perform differently?

Again, thanks for helping.

Bruce, with many more questions...

[steve simmons]

Before buying a camera, if you have not done so, I suggest reading

Getting Started in Large Format. It is a free article on our web site

www.viewcamera.com

hit the Free Articles button on the black menu bar

steve simmons

It will give you some guidelines for determining how long a bellows you need.

[Bruce McCrory]

Steve, ..35x3=(4x5) lens relation; focal distance x 1.2-2.0 = bellows extension. I did read the referenced article in View Camera. It was the reference I couldn't recall for bellows approximation together with 35mm/YxZ format relationship. I have seen several references to your book, "Using the View Camera". Are you also connected to the View Camera Store in Phoenix?

Will a Deardorff 5x7/4x5 (22-23"/550-585mm bellows) work? [As he ignores the point of the article, and Steve's suggestion.] I'm working on lenses. And, tripods. Meters, filters, film, film holders,.... hernia support.

Thanks, Bruce McCrory

[Don Wallace]

Nick hit the nail on the head. It sounds like the answer should be "as much bellows as you can get" but you need to determine what lenses you want to use. I have a Wisner Technical Field with a very long bellows but I did not take into account the fact that my most used lenses are 90, 150, and 210. The 150 and 210 are fine but I have to switch to a bag bellows to use the 90, which is a huge pain in the arse. I am going to get another bellows made that will accomodate these lenses without the necessity of changing to use the 90mm.