Sir Isaac Newton co-invented calculus. He was a very clever man. The Camera Obscura has been known since ancient times and the lens has been known at least from the 1300. They had the camera (obscura) in Tudor times in England and made wonderfully accurate paintings using them. The pinhole camera obscura was known in Roman times. Wavelength is important when considering diffraction and a formula 2d/lambda where lambda is the wavelength and d the diameter of the aperture is important. I think it defines the minimum angular separation (in radians) that may be distinguished by a particular optical system. This limits all optical systems. However a pinhole causes a tube of light from a distant object to be cast upon a screen the diameter of this tube is the same as the pinhole and makes a circle of light on the screen. This is the circle of confusion. It would seem that the further away the screen is for a particular pinhole the smaller effectively will be the circle relative to the total size of the image, however the light gets dimmer and diffraction will limit the resolution. So there will be an optimum size of hole for any particular pin-hole screen distance. As a guess I would say it would be where the diffraction effect limited the resolution. But I cant work out a reasonable answer from this supposition. Chris http://www.chrissdomain.com -----Original Message----- From: owner-photoforum@listserver.isc.rit.edu [mailto:owner-photoforum@listserver.isc.rit.edu]On Behalf Of Qkano Sent: 19 September 2002 08:17 To: List for Photo/Imaging Educators - Professionals - Students Subject: Re: Focal Length Redux > > Consider it an exercise for supercilious twits. > > Hmmm. No Steve remember, in the days of "dumbing down" accuracy, detail and correctness are scorned upon. The "sound bite" generation is driven by the belief that if you can't understand something without thinking about it then it is BS. All your attempts to bring in wavelength, are just adding to the circles of confusion that surround most people's understandings of optics. Issac Newton - WTF did he know about modern cameras anyway? Lot of mental mast. that bloke - hypercilious twit by today's standards! > Cropping causes issues though... Cropping changes the focal length of the lens ... we all know that. Q
