col
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Posts: 329
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Post by col on Nov 3, 2012 5:44:05 GMT -5
Work in Progress This is the plan.. make three of four lens less cameras. Take a bundle of pictures..and if all goes well. Use many of the the images in an exhibition, sometime late next year. The provisional title ... 'Lensless-in-Albany' The first camera will be a large format pinhole made from timber. But will start by testing using one of my foam board cameras And the first series will have the theme ' Woodlands' so I have purchased a box of Efke IR film and run the first test (without filter) so I can work out the base exposure. Image 001 my back garden (test only) f217 6 seconds. Did have one slight problem flapping light seal, caused a shadow on the right hand side.  |
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Stephen
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Still collecting.......
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Post by Stephen on Nov 3, 2012 7:32:52 GMT -5
Will foam board work with IR? It must pass more IR than wood, but it a very good heat insulator, so may well block all IR.
If it does pass any, then an aluminium foil inner liner would stop it. I presume it has to be painted black to light proof it anyway? I use foam board for model making a lot, but had not thought of it for pinhole cameras. mine are not for film, I use paper negs for scanning to positive.
I use a sheet of 1 thou stainless steel foil for the aperture, and make the hole with a needle, pressing against hard wood, this leaves to dimpled out hole at the back, then turn over and and sand with 5000 grit emery to end up with a hole with the rim only a few microns thick. it can be chemically blacked or smoke blacked.
Stephen.
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col
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Post by col on Nov 5, 2012 19:29:13 GMT -5
Hi Stephen "I use a sheet of 1 thou stainless steel foil for the aperture"
how do you work out the size?
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Berndt
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Post by Berndt on Nov 5, 2012 20:56:21 GMT -5
Interesting project. Looking forward to following its progress.
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Stephen
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Post by Stephen on Nov 6, 2012 17:07:53 GMT -5
Hi Stephen "I use a sheet of 1 thou stainless steel foil for the aperture" how do you work out the size? The diameter of the pinhole "hole" varies a bit, but from 2 to 4 thou across, measured with a loupe lens that has a graticule scale, in other words a simple measuring microscope. It needs as small as practical, at 2 thou the exposure can be very long, hours, the largest I have used is about 25 thou, faster but less detail. An f stop is difficult to estimate as the pinhole to film distance varies across the frame, but in relation to the centre is calculatable. The best pinhole cameras has a curved film plane as a radius from the pinhole on the horizontal plane, the vertical plane is flat of course, unless you coated the inside of a ball shaped "film" with emulsion! I use postcard size paper or film, at 4 inches from the pinhole, with a "Hood", a shade on the outside to minimise stray light falling on the pinhole The stainless steel is foil from scientific instrument recorders, stronger than aluminium foil, which can be used with direct pinholes as well. The foil is postage stamp size, glued to a card as the front lens board of the camera. It is smoked black with candle flame smoke before use, this prevents flare and increases detail. Stephen. |
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Stephen
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Still collecting.......
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Post by Stephen on Nov 6, 2012 17:17:53 GMT -5
F stop is diameter of the hole divided into the pinhole to centre of the film distance , so 4 inches equals 4000 thou, divided by say 5 thou, equals an F stop of 800. (25 thou would give F160).
However although this gives a ball park figure emulsion of any type suffers reciprocity failure at long exposure times and the actual exposure could be up to 5 to 10 times the expected figure.
Stephen.
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Stephen
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Still collecting.......
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Post by Stephen on Nov 6, 2012 17:40:25 GMT -5
There are several sites on the net giving exposure times in terms of F stops, most seem based on bigger stops of up to 1mm diameter, this gives poor definition, the tiny ones I use suffer from diffraction a bit at 10 thou, more at 5 thou. Mine would be too small for 5x7 negs, but perfect for 35mm( you can add pinhole to any reflex camera or rangefinder), and 5 thou works.
Stephen.
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col
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Post by col on Nov 6, 2012 22:18:51 GMT -5
Stephen I go the easy way. I buy EMS pinholes from a guy in the USA for just $1 each + $5 postage
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mickeyobe
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Post by mickeyobe on Nov 6, 2012 22:31:42 GMT -5
Stephen I go the easy way. I buy EMS pinholes from a guy in the USA for just $1 each + $5 postage This just proves how crazy we camera collectors are. $6.00 for a tiny hole!!!! Mickey  |
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col
Lifetime Member
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Post by col on Nov 6, 2012 23:00:07 GMT -5
Mickey how true...I guess hole could be free.. it's the metal around it that one pays for.
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hansz
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Hans
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Post by hansz on Nov 7, 2012 4:00:28 GMT -5
Reminds me of one of my customers, an aerospace parts producer.
They made beautiful milled metal parts, worth $ thousands, 2kg out of 200kg metal.
I asked the manager what more high tech parts his plant produced.
He just looked around, saying: "chips".
Hans.
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