Archived posting to the Leica Users Group, 2001/08/02
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I agree; my mistake. I should have researched it a bit more before making any statements about it. Unfortunately, I don't recall the context in which I made the statement, so I'm unable to assess the impact of my error on whatever my original argument was. - ----- Original Message ----- From: "Johnny Deadman" <john@pinkheadedbug.com> To: "LUG" <leica-users@mejac.palo-alto.ca.us> Sent: Thursday, August 02, 2001 14:21 Subject: Re: [Leica] mxsmanic and pinholes > on 8/2/01 12:32 AM, Mxsmanic at mxsmanic@hotmail.com wrote: > > > Jimmy writes: > > > >> That is utter rubbish. > > > > In what way? Pinholes have no aberrations or distortions at all; they are > > diffraction-limited. No glass lens can match that, no matter what its design. > > The only real reason to use a glass lens at all is that pinholes require very > > long exposure times. Glass provides some other conveniences, also, but better > > image quality is not one of them. > > Sorry, you are really up the creek on this one. The image quality of a > pinhole camera increases with diminishing size of the pinhole up to the > point at which diffraction effects start to become more significant. > > This puts a clear limit on resolution. > > Contrary to what many people think the diffraction effects are significant > even when the diameter of the pinhole is *much greater* than the wavelength > of the light involved. The maths are not very difficult and agree well with > experimental results. The maths also tell you that a pinhole of a certain > diamter has an optimum focal length associated with it. > > So, what is the resolution of a pinhole lens in the best-case scenario of > optimum diameter and optimum focal length? Some experimental results can be > seen here: > > http://www.pinhole.com/resources/articles/Young/ > > They seem to me to show that the maximum possible resolution of a pinhole > camera, is about 5 lp/mm. That is an order of magnitude less than not just > Leica lenses but most commercially available 35mm lenses. > > -- > John Brownlow > > http://www.pinkheadedbug.com > > ICQ: 109343205 >