Muggins
Junk magnet
Assuming it really is a 32mm push-on filter, they're common as muck - it really was a common size in the 1950s, Kodak made them by the million and they weren't alone. Ebay should be heaving with them.
I've used Humbrol Matt 33 enamel paint (not sure if it would be available in California, though) for touching up scratches where I've *cough* made a mess removing the slotted ring. Applied thinly with a very small brush, I was surprised to find that 24hrs later I couldn't see where I'd applied it, it was so good a match. But don't get it in your shutter...
Adrian
I've used Humbrol Matt 33 enamel paint (not sure if it would be available in California, though) for touching up scratches where I've *cough* made a mess removing the slotted ring. Applied thinly with a very small brush, I was surprised to find that 24hrs later I couldn't see where I'd applied it, it was so good a match. But don't get it in your shutter...
Adrian
charjohncarter
Veteran
Thanks, I just looked in the film and bellows compartment. There are some areas of missing paint. I'll try to figure out the hood this week.
Windscale
Well-known
Any progress?
charjohncarter
Veteran
I don't think I know what I'm looking for. I still in the fishing stage.
Windscale
Well-known
Tell us the diameter of the front focusing ring.
Just paint to cover any reflections you can see inside the film compartment.
Just paint to cover any reflections you can see inside the film compartment.
charjohncarter
Veteran
Thanks, It looks like 32 mm, I hope it isn't 33mm. I have some flat black Ace Hardware paint that I very carefully used to cover the shiny chipped spots. I hope to find a rubber hood at a good photo store in Berkeley, CA (Looking Glass). Wish me luck.
FallisPhoto
Veteran
Where did you look to find the correct lens-to-film-plane distance so you could get it to focus right?
dazedgonebye
Veteran
See, this is why I stick to pinhole conversions.
I measure after the fact to guess at the focal length and nobody cares if something isn't straight.
Good on you guys for being so handy though.
I measure after the fact to guess at the focal length and nobody cares if something isn't straight.
Good on you guys for being so handy though.
Windscale
Well-known
The focal length of the lens would give you a rough idea of the distance, say 75mm, 80mm or 47mm as the case may be. The actual measuring can be done by mounting the camera on a firm tripod, opening the film compartment and taping a piece of ground glass on the film plane. Then you physically open the lens wide to B and hold it in front of the camera to get a focus of infinity by looking through the ground glass with the help of a lupe (8X or higher). You then measure the distance between lens and film plane and start making your adaptors based on that distance. The end products can be fine tuned by using spacers in case of lenses focusing on front lens element, or by adjusting the focusing mount in the case of lenses whose focusing is by moving te whole lens if it has one. This is not difficult but can take a long time to get it right.
Windscale
Well-known
This is simple. You either get someone to help you or you mount the lens on another tripod with a clip or something that holds and move that other tripod.
FallisPhoto
Veteran
Thanks! Your last post wasn't making any sense at all without this one. Unless you have a simple one-element lens, the focal length of the lens has nothing whatsoever to do with where the lens board goes. The focal length of a lens is the effective distance between the center of the front lens element and the film plane, but when you get into lenses with more than one lens element, this is almost never the actual distance, because the light path gets folded and/or bent several times between the front element and the film plane. I mean, look at the difference between where 50mm lenses are located on rangefinders and SLRs.
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Windscale
Well-known
Sorry about that. As I have done it so many times sometimes I do take things for granted without appreciating that others may not be so familiar with the procedure. You will also see the image better if you covered the whole setup with a piece of black cloth, like you shoot big LF sheet film in the old days. I hope you will succeed in making your 'moonshine' camera. Do let us know how you get on.
So, from now on, you will keep all the odds bits such as lens tubes, lens caps etc as you may use them for your own mods.
Read your edited post: It does not matter about actual or effective focal lengths. You will be measuring the distance of a specific point in the lens (be it the front element, rear element, rear side of shutter or wherever you like) to the formed image (as seen on the ground glass). That distance must be the right film to lens distance.
So, from now on, you will keep all the odds bits such as lens tubes, lens caps etc as you may use them for your own mods.
Read your edited post: It does not matter about actual or effective focal lengths. You will be measuring the distance of a specific point in the lens (be it the front element, rear element, rear side of shutter or wherever you like) to the formed image (as seen on the ground glass). That distance must be the right film to lens distance.
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FallisPhoto
Veteran
Not so. Yes, it has to be the right distance, but only god and the lens manufacturer know what that distance is. As stated in my post, the actual lens to film plane distance is not the same thing as the actual physical lens to film plane distance because it depends on the design of the lens. For example, this 500mm lens http://www.mflenses.com/gallery/v/lensgallery/russian+lens/rubinar500.jpg.html acts like it is several times longer than its physical length, because the thing uses mirrors to fold the light path. If you located this lens with the center of the front lens element 500mm from the film plane, it would be from 3 to 6 times too far away, depending on how many times the light path is folded inside the lens.
While a simple one-element lens with a focal length of 50mm is exactly 50mm from the center of the front element to the film plane, more complex lenses bend the light path and alter the cone dramatically (sometimes the light path converges and sometimes it diverges, only to be brought back to convergence again, and this can happen several times). This takes up space.
To show a really obvious example, retrofocus lenses (what you find on SLRs) focus the light so the light cones converge further back than they do with rangefinder lenses. They do this because they have to compensate for having to focus past the mirror boxes on SLRs. This means they have to be physically more distant from the film plane than would be the case if you were using a non-retrofocus lens of the same focal length, such as is found on a rangefinder.
Even a non-retrofocus 7-element lens of 50mm would have to be located with the center of the front element more physically distant from the film plane than would be the front element of a simpler 3-element lens, because the light path in the 7-element lens converges as a cone and then diverges as an inverted cone several more times on it's way to the rear element than would be the case with a 3-element lens -- and that also requires more space.
In simple terms, a three element 50mm lens on an Agfa Isolette, like an Apotar, is a lot shorter than a 7-element 50mm lens on a Pentax K1000 and needs to be located closer to the film plane too. If you take two dissimilar 50mm lenses, like a 50mm Apotar and a 50mm Pentax SMC, and locate them so the centers of their front elements are the same distance from the film plane, then if the Apotar is about right, the Pentax lens will be way too close.
It was that second post of yours that explained it. Trial and error. You focus the lens for infinity and just move the camera or the lens closer or farther away until it looks like it is in focus, THEN measure the distance and build your lens board that thick.
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Windscale
Well-known
I am sure you are right. But I have only done mods with lenses with which I can measure the lens to film plane distance with reference to the image formed on the ground glass. The stated focal length of the lens (say 75, 80, 85 etc.) will only be a rough guide to start with. They are never exact. And that's why fine tuning was necessary.
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Windscale
Well-known
It is not a matter of "looks like". It is sharply in focus. In the case of lenses which focus on the front lens element, it is best not to move the original front lens element before doing the measurement. Although it may have been displaced from a perfect focus position, it should not have been displaced too much. After measurement, fine tuning would be easier. And it is important to check infinity and one more distance (say 10 feet or 15feet) before putting the lens in position for the very fine tuning.
Agfa Solinar 75/3.5 on Zeiss Nettar as in my Avatar
Agfa Apotar 85/4.5 on Agfa Click
Rolleiflex Planar 75/3.5 on Agfa Isolette
Schneider Kreuznach 47/5.6 on Agfa Isolette and Perkeo I
Schneider Kreuznach 65/8 on Bessa I
Voigtlander Color Skopar 75/3.5 on Agfa Click
All their focusing distances were obtained in the way I mentioned.
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FallisPhoto
Veteran
I do a lot of writing and I pick my words carefully. If it has been displaced from a sharply focused position, and I don't see how to get it exact while you are shifting large tripods with a camera on one and a lens on another, and then measuring it, it isn't sharply focused. Otherwise, fine tuning you keep mentioning wouldn't be necessary. You get it to where it looks focused and then fine tune it so it is sharply focused.
Windscale
Well-known
When the lens and the body are both on tripods you do get a sharply focused image. The ground glass never lies. But this is only to give a guide distance because that distance is very likely to be a bit out once all the parts (board, adaptor tube etc.) are put together, maybe just by a fraction of an mm. That's why fine tuning will be necessary. Anyway I am sure you will appreciate the facts once you started doing it. It is very different from just writing about it. I am not much of a scientist, I just get things done by measurement and checking with ground glass. Obviously you are the technical expert. But if you do get too technical, things will be beyond me.
Thank you for your views and I think we have spent enough time on exchanging views on some rather simple matter. If you are really going to do some mods I would be glad to help you out.