cheap lens for DIY ULF

[Janko Belaj]

O.K... that is kind a "stupid" idea, but I hope it will be fun. ;-))
Idea is to take graphic art film, place it in a box of TV, refrigerator or whatever. In few boxes - as many as I can put in a car. And than - on the front "panel" some lens... anything better (i.e. faster) than pinhole. Any ideas what to look for?
tnx :-)

[Mark Fisher]

Might do a search for a zone plate. It is a set of concentric rings alternating clear and opaque

[Janko Belaj]

he! this IS fun: Whiz Kid Technomagic Zone Plate Designer (http://www.whizkidtech.redprince.net/zoneplate/)... now just to find out what the ISO might be for my film... and, to use it as IR film or as a normal film?



However, I would still like to place a peace of glass... but what kind of glass that should be? any thoughts? Any knowledge if I can use some magnifying glass?



Tnx again! ;-)

[Bruce Schultz]

Ideas for the ultimate extra large format camera:

Use an old van. Board up the windows and cut a 1-inch hole in a back door. Seal the space behind the seats for the film holder. Voila.
Better yet, use a moving van. Use one of those RV backing-up cameras to frame the image.
But a refrigerator box in the back sitting in the bed of a pickup might work as well and would be a lot cheaper.

You wouldn't need a tripod, and it would follow Weston's philosophy that pictures aren't worth taking if they require walking from the road.

[Joe VanCleave]

I've built several LF cameras using improvised lenses. One used a small credit-card sized plastic fresnel magnifier, focal length around 3.25 inches. I stopped it down to 1/4" aperture, to give f/13, and attached it to my Speed Graphic. I had to run the bellows back, and even with dropping the front of the bed, still had a bit of the bed in the picture. I used the focal plane curtain shutter to time the 1/10 second exposure on paper negatives.

For your project, first look at what focal length you're using. Then you'll have to find a lens that accomadates that focal length.

I've used an objective lens from a 50mm binocular. It just unscrews from its housing, and the focal length was around 150mm. Built into a foamcore box, it covered 5x7 with no movements, and was really sharp, as its a coated doublet.

For longer focal lengths, you'll just have to look at magnifiers at stores and see what distance they focus to. I'd advise, especially with single lens setups, to stop down considerably to improve image quality and widen depth of focus.

[Craig Wactor]

The front element of a process lens could work. They are pretty long, with big coverage. Also, I have wanted to try a condenser lens from an enlarger. Peeking through one it looks like it could work.

[Dan Fromm]

Hmm. Any lens long enough that will form an image will do. But what's the point of taking large crappy paper negatives when you can get better large prints starting from 35 mm? IIRC, Janko, you have more than one 35 mm camera already.

Cheers,

Dan

[Christopher Keth]

Because getting large negatives, crappy or not, is much more interesting when approached this way than doing things with a 35mm camera. :)

[Janko Belaj]

Joe, focal length isn't defined yet, and will be approximately the length of the box I will use. I see now that I didn't mentioned film dimensions - I did mention that I might use a refrigerator box, and that is huge... well, I'm thinking about 50x50cm (that will be 20x20 inches) or larger up to 70x100 or so cm... So, I'm trying to find "lens better than pinhole" to cover such sizes. and it really doesn't meter what size it will end - I'm not interested (now) in building such camera - I would just like to have some fun with such sizes.
Dan, I'm not talking about crappy paper negatives, but about (maybe unproper) graphic art film - the one which goes in imagesetters. 76cm wide, way longer. And I have access to lot of that film, processing engine and can play with developers, temperature and time to take out something. what will that be? Have no idea at this very moment, but I hope that it will be *fun*. and that is all. fun! joy. pleasure... ;-))
And yes Dan, I have more that one 35mm, MF, LF cameras, but now (for next few months) I have that imagesetter's developing processor left for good in unused room next to my studio...

[Dan Fromm]

Janko, thanks for the additional information. What an interesting opportunity you have!

A narrow angle process lens typically covers ~90% of its focal length. So for 50 x 50 you'll need at least an 800 mm lens. 70 x 100 wants at least a 1400. They exist...