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 Originally Posted by Reinhold
The RB-67 has a bayonet mount and a bellows bellows focus system, but lacks a focal plane shutter.
That didn't stop me from machining an acetal bayonet ring to which I mounted an PVC tubular barrel into which I installed a Meniscus lens.
Of course, timing is "iffy", since I use the Top Hat Shutter system.
It works.
Very nicely.
Take a look...
Reinhold
www.classicBWphoto.com
That has some nice results it seems. So two questions for you: When I tried making a single meniscus for my 4x5, I didn't have enough bellows draw to focus it at infinity. I'm assuming that the rb67 has less bellow draw than my cambo, so how did you make it work? And number 2: how do you figure out what your f-stop is? trial and error? comparison with other lenses with known f-stops? is there a measurment you can take? I really want to figure this out...
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Austin,
For my RB, I used a 125 mm meniscus lens.
If you didn't have enough bellows draw with your close-up lens, it was probably a + 2 lens.
A +2 lens has a 500 mm focal length. (You'd need 20" of bellows just to focus at infinity)
A +4 lens has a 250mm focal length, and would probably work on your Cambo.
(Depending on how close you want to focus)
f-stop is simply the focal length of the lens divided by the diameter of the lens opening.
I now enclose a simple "Tips on using soft focus meniscus lens" page with my lenses.
If you'd like, I'll PM a copy to you...
Reinhold
www.classicBWphoto.com
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Originally Posted by Reinhold
Austin,
For my RB, I used a 125 mm meniscus lens.
If you didn't have enough bellows draw with your close-up lens, it was probably a + 2 lens.
A +2 lens has a 500 mm focal length. (You'd need 20" of bellows just to focus at infinity)
A +4 lens has a 250mm focal length, and would probably work on your Cambo.
(Depending on how close you want to focus)
f-stop is simply the focal length of the lens divided by the diameter of the lens opening.
I now enclose a simple "Tips on using soft focus meniscus lens" page with my lenses.
If you'd like, I'll PM a copy to you...
Reinhold
www.classicBWphoto.com
yes it was a +2. Well i will try and pick up a +4 soon, hopefully that will work. And thank you for the information! 500 is definitley too long for my cambo haha. But I will keep the +2, so i can use it one day when i get an 8x10. For now though, i am sticking with the 4x5. I would very much like a copy of that, if it's not too much trouble! Thanks!
oh and how do i figure out the focal length with a random element?
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I have a big box of assorted lenses just for optical experiments and building "funky lenses"... most are from old 35mm-SLR lenses, that were broken beyond repair. They mostly get used with 35mm film, but a few are good for larger formats. One cheap 200mm/4 lens gave me the front lens with about f=400mm and and an achromat (two elements glued together) with f=200mm. Both are either very soft LF-lenses (covering 8x10 is no problem, though the camera for that is just a cardboard box) or close-up lenses for Kowa Six lenses. I never got the hang of the "hat-shutter", though... Having the small apertures necessary for slow shutter speeds gives too much DoF and sharpness for my taste.
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Originally Posted by Rick A
My faves are 6x9 or 6x6 lenses(80-100mm). For some reason, I'm fascinated with the port-hole look of the image(vignetting).
I was recently given a Kodak Senior Six-16 camera with a 123mm lens (I think). I am converting the camera to 120 film and whilst I had the lens removed, I tried it on my Speed graphic and was surprised to see full coverage. I have also had full coverage of 5x4 with a Kodak 105mm lens from a 6x9 camera.
It's also fun to play around mixing up front and rear cells which weren't meant to go with each other.
Steve.
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You can get a reasonably accurate measure of the focal length of a lens by temporarily taping it to a blank lensboard on your 4x5 camera.
If you don't have a lensboard, hack one out of a piece of stiff paperboard.
Focus on an object far away (close to infinity), and measure the distance from the lens to the ground glass.
That's the focal length.
Reinhold
www.classicBWphoto.com
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I use an old magnifying glass as a lens on my venerable 4x5 Graphic View, with a focal length of about 95mm/3.75-inches. It has a maximum aperture of about f/2.8, and I have a set of home made diaphragms which go down to f/48.
It flares like crazy, and I have found that when working outdoors, the best course is to use a lens shade, as well as a #16 or #25 filter to "tame" the sky a bit.
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