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Yer welcome. Go to B&H and check out pinholes to see the range and size/focal relationships. Go to the Bender website (still up after all these years) to see a really cool pinhole system, one that allows ground glass viewing of the image. Bender is out of business of course so I can't order the system but I'm going to attempt making something similar.Quote:
Originally Posted by StoneNYC
Pinhole cameras are wonderful devices with infinite DOF (with some reservations). There is generally an optimum pinhole diameter size d for a particular focal length F and wavelength of light lambda, a relationship first postulated by Petzval (yes that famous that old timer), such that D = (2 X FX lambda)^1/2.
So for the image above when we apply the Petzval relation we have D = (2 X 75 X .0005)^1/2, which is the sq. root of 0.075 which is .274 mm. That is 274 µm or about 11 mil diameter hole.
The f/no would be FL/d which is 75/.274 which is f/274. He obviously used a slightly different aperture diameter or a different value for lambda. :)
Nate Potter, Austin TX.
I have a Zero Image 4x5 pinhole camera with two extension frames. This means I can shoot 25mm, 50mm and 75mm focal lengths all using the same 0.18mm pinhole. Ideally I would use the "optimal" pinhole diameter for each separate focal length, but I haven't found it to be a problem other than the fact that the f/138 aperture at 25mm becomes a whopping f/417 at 75mm.
Jonathan
I wish I understood that math... My head hurts... I used to be good at this stuff but it's been 10 years since I did any math at all.Quote:
Originally Posted by Nathan Potter
Qué maravilla, Jose. No sabía que tenías una de éstas. Abrazos.Quote:
Originally Posted by Jose Rodriguez
Great photo, Jose. I didn't know that you had that camera. Nice surprise. ;-)
Best regards.
Beautifull...Quote:
Originally Posted by Ken Lee
I like this, very much...Quote:
Originally Posted by Nguss
Well done, Preston.Quote:
Originally Posted by Preston
I try to do the same but, I use split-contrast, too, wich gives me a lot more possibilities, but, sometimes it's hard to get what I want. What's really missing in the darkroom is the "undo" button! ;-)Quote:
Originally Posted by ScottPhotoCo
Stone, I hear ya. Math is a bit like language - if you don't use it regularly it slips into the dark recesses of the mind where it can't be easily extracted. I have that trouble with higher math and I work high tech solid state physics all the time. Notice that Einstein and Stephen Hawking had fellow mathematicians helping them. I believe Einstein used David Hilbert and Hawking uses Roger Penrose.
My note above only uses simple algebra and my example should suffice for the novice. But the notation may be unfamiliar, particularly the form of ( X )^1/2. That is just another way of saying the square root of X. Or √X. Use of the ^ indicates something like X raised to a power or an exponent - rather awkward notation due to the standard keyboard being unfriendly to math symbols.
Nate Potter, Austin TX.