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  #11  
Old 20th April 2012, 09:50 AM
Alan Clark Alan Clark is offline
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I read somewhere that diffraction degrades the image if the hole is made in thick metal , and one way round this is to lay the metal (from a drinks can, eg.) on a flat wooden surface and press a dent into it using a ball-point pen. (Don't make a hole.) Then turn the metal over and carefully remove the top of the raised pimple with very fine wet and dry abrasive paper stuck to a flat board. The resultant hole will have a knife-edge. Hole diameter can be checked with an enlarger or flatbed scanner, and the result is supposed to be a "pinhole" of superior quality.
However, when I tried this and fixed it up to my 5 x 4 camera the results weren't very good at all! I got much better results with a pinhole from the now defunct Retrophotographic. This was not lazer cut, just made with a drill bit, though the foil is very thin.

Alan
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Old 20th April 2012, 12:40 PM
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On checking this morning I have found that Acupuncture needles are available in quite small sizes and reasonably cheaply. They seem to range from about 0.16 mm to 0.3 mm and are around £3.50 per 100. That gives plenty of spares for when they bend or break!

Bill
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  #13  
Old 20th April 2012, 11:51 PM
BobRob BobRob is offline
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Just to add this comment from an article I saw somewhere regarding
the quality of the pin-hole.

the roundness of the hole is thought not as critical as the smoothness of the edge or the thickness of the shim used

A rough hole or an over thick shim are stated to be factors that will advesely affect image sharpness and of course angle of view.

an oval hole will produce a different image but not be obvoisly less detailed.

Personaly I am working towards finding the ultimate sharpness but fully expect to draw back from that possition to produce the softer effects that I seek.

bobrob.
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Old 22nd April 2012, 04:25 PM
Dave miller Dave miller is offline
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As you require "ultimate sharpness" Bob I wonder if you have considered using a lens?
I thought pinholes were meant to be a bit fuzzy.
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  #15  
Old 23rd April 2012, 07:45 AM
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Quote:
Originally Posted by Dave View Post
I thought pinholes were meant to be a bit fuzzy.
What I am trying to find out is how big is the bit?

I think a good pinhole example is Wiesmier's recent posting of the beach scene. It's a pinhole image that still looks sharp. My current attempts are not as sharp as that so I have work to do, probably on the size of the pinhole.

Bill
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