Archived posting to the Leica Users Group, 2001/08/02
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
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