I wish to take close-ups of small flowers, say 3 inches in diameter, with a 20x24 camera with a Goerz 762mm lens and have this image cover the film. I built the halfsize of a refrigerator camera and figure I could build another much longer camera. What would my depth of field be with 20 feet of bellows at f64. Is this just to rediculous to consider. I love this camera and the results. I also love my Rollei 35, Contax with Zeiss 1.4, Rollieflex, Zeiss Ikonta, and homemade 4x5 with 100mm Wide Field Ektar, but nothing compares to the 20x24. Any suggestions?

-- Mark Stevenson (marks@cwo.com), November 28, 2000

Answers

At 8x life size, approximately 54mm at f64. Not much at that magnification and f-stop. You could close down to f128 and stretch it to a little more than 1cm. Good luck! ;^D)

-- Doremus Scudder (ScudderLandreth@compuserve.com), November 28, 2000.

Please post a picture of your 20x24 camera!

-- fw (finneganswake@altavista.net), November 28, 2000.

How many days long will your exposure be?

-- Steve Clark (Poophappens@aol.com), November 28, 2000.

Based on the equations in the back of one of A.Adams books, a 762mm f11 lens with 6.2 meters of extension; magnification would be about 7.1X, f11 becomes f90, f64 becomes f540, depth of field would be about 2 inches at f540.

Instead of a bellows, why not use a an old Extended body van or bread truck, and put your negative on a moving track (Sort of the same idea as Adams' horizontal enlarger). Just back it up to your subject, set the parking brake, focus, and snap away.

I do have a 14'steptruck. Just looking for a 1400-1800mm lens. Closest I've found is a single element Nikon close up (0.7)lens. Same idea as the guys that used a VW van as a large mobil pinhole camera.

-- Beau Schwarz (ejschwarzjr@hotmail.com), November 28, 2000.

Why not use a much shorter lens, say 90mm? If its coverage is 230mm at infinity focus (i.e., bellows extension = 90mm), then its coverage will be 2.3 meters when bellows extension is 0.9 meters, for example. The point is that you don't need lenses with huge coverage for close-up wor

-- Stewart Ethier (s_ethier@parkcity.net), November 28, 2000.

Wow, Beau, that must have been some pinhole camera! I remember an article in Shutterbug about building a pinhole "zoom" which consisted of a long tube between the pinhole and the film. I see it now: "Uh, no, officer, that's not a rocket launcher on my roof rack. It's a set of 8x10 pinhole cameras with zoom attachments..."

-- Brian C. Miller (brian.c.miller@gte.net), November 28, 2000.

I'm not sure about the depth of field, but a year or three ago there was a short article in National Geographic regarding a photographer who used an 8x10 with about 20 feet of extension to photograph insects with some pretty awesome results. I'm not sure if it would help you much, but it at least it illustrates that things of this sort have been done successfully in the past and could probably be done with equal success today. Good luck with your project and keep us posted on any progress.

-- Dave Munson (orthoptera@juno.com), November 28, 2000.

The camera is just a box with a lens. Here it is. It's at the end of the bench with the two brass handles. Refrigerater is behind with part of a contact print from the camera visible.

-- Mark Stevenson (marks@cwo.com), November 28, 2000.

Why not use a much shorter focal length lens? At lifesize a 360mm lens will cover, and only needs 720mm of bellows, at 1:2 you could use a 210mm lens, and so on.
If you're considering filling the frame with a 3" flower then this is 6 or 7 to 1, and a reversed lens of about 100mm focal length would be ideal.
Remember also that your effective f number is multiplied by (1 plus magnification), and that a marked aperture of f/64 at the end of 20ft of bellows will be f/400, or thereabouts, with a diffraction limit of about 3 line-pairs per millimetre. A 20x24 enlargement from 5x4 or medium format would easily be sharper than this.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 29, 2000.