Kent Shafer
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Kent Shafer last won the day on August 17 2016
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Cursed Panatomic X
Kent Shafer replied to royall_berndt's topic in The Wet Darkroom: Film, Paper & Chemistry
I have nothing profound to add but am using this as an excuse to post a picture of an old friend from back in 1965. Yashica Penta J, 50mm Auto Yashinon, Panatomic-X developed in Diafine. -
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I've had my Marchioni Tiltall for (gulp) about 50 years. Maybe 20 years ago, I replaced the top covering with automotive cork gasket material; don't remember what type of cement I used. It has worked fine ever since. I've used the tripod mostly with a Calumet monorail (rotating back) or Hasselblad so haven't needed to tip the head on its side.
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Here's a link to an online calculator you may find helpful: https://www.scantips.com/lights/subjectdistance.html It shows that with a standard 24 x 36 mm sensor and a 500 mm lens, the subject distance will be about 21 times the size of a subject that just fills the short dimension of the frame.
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Orion Werk Tropical 9x12 restoration
Kent Shafer replied to andrew_spence1's topic in Classic Manual Film Cameras
Beautiful! -
Film Camera Week for November 16
Kent Shafer replied to Mike Gammill's topic in Classic Manual Film Cameras
One from the archives for me too. Calumet CC-401, 215mm Ilex Caltar, 1/125 @ f/8, Kodak Super-XX developed in D-23. Snow Fence -
Linhof Technika Serial Number Questions
Kent Shafer replied to Glenn McCreery's topic in Large Format
Got it—thanks! -
Linhof Technika Serial Number Questions
Kent Shafer replied to Glenn McCreery's topic in Large Format
Thanks. Maybe this one's about the right vintage to go with my 1960 Technika IV, which is what I was hoping for. Thanks again for all your help! -
Linhof Technika Serial Number Questions
Kent Shafer replied to Glenn McCreery's topic in Large Format
Is it possible to know the date of manufacture of this Linhof Optical Multifocus Viewfinder? I can't find a serial number on the finder itself, though there are numbers of some kind on its box. -
Bob, yes, exactly right. Depth of focus, rather than depth of field, would seem to the relevant consideration in determining the precision required in camera construction.
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Your question relates to depth of focus, that is, the distance between the farthest plane in front (toward the lens) of the perfect plane and the farthest plane rearward from perfection within which the image will be in acceptably sharp focus. The answer depends on the focal length of the lens, the f/stop used, the subject distance, and one's definition of "acceptably sharp." I'm no expert on this stuff, but I found your question interesting so took a look at the Wikipedia article on depth of focus. The article has various formulas for calculating depth of focus, including this simplified, rough-justice one that eliminates the focal length and subject distance variables: t ≈ 2Nc, where t is the total depth of focus, N is the f-number, and c is the circle of confusion (the "acceptably sharp" variable). A commonly used value for c for 4x5 film is 0.1 mm. Using that value, the simplified formula would yield the following depth of focus ranges: f/4.5: 0.9 mm f/8: 1.6 mm f/22: 4.4 mm Since those are total ranges, front to back, the margin for error in camera construction would be half the calculated amount. Say about plus or minus 0.5 mm for wide-open shooting. Using the good advice from earlier posters, it seems you could achieve much better precision than that. Of course, hardwood will expand and contract a bit with changes in humidity, which could eat up some of the margin for error.
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