diffraction curiosity questions

Hello:

I am curious about diffraction's role in photographic imaging, if any.
That's my background, with some physics from an engineering
curriculum. SO I hope to understand replies, just lack enough
education to my question myself. I'm not in the sci.optics filed, so I
realize there is some inherent ignorance in my questions.

I noticed in a few classic optics texts that a chapter on diffraction
appears to be the starting point for imaging. The simplest example of
interest to photographic imaging is the circular aperture. It and the
slit are apparently the only things simple enough to attempt a
rigorous text derivation of with minimal assumptions and
approximations.

Rayleigh may have used the phrase 'Imaging without refraction or
reflection' in his paper on resolution limits.

This leaves only diffraction. To me, it's intuitive that diffraction
is the only reason a pinhole image is produced that is much wider than
the pinhole aperture. The index of refraction is the same on either
side of a pinhole aperture. A pictorial image is just a more complex
situation than a laser demonstrating diffraction with an aperture.

It occurred to me that many photographers are obsessed with and
misunderstand diffraction. They lust for 'diffraction-limited' optics,
and thus assume by judicious use of their equipment they can avoid
diffraction 'effects'. I also hear pinhole photographers talk of
avoiding diffraction or "too much" diffraction. I believe this should
only be relevant to a loss of resolution from too small an aperture

I am getting to my question...it occurred to me that I remembered a
lens or an aperture both act as (or at least can be modeled/explained
as) a Fourier transformer. The aperture function is present in both a
lens (whether is has an iris or it's own clear diameter inherently
limiting it as an aperture) and in a circular pinhole aperture.

Is it not the case, then, that diffraction is the method by which
imaging occurs in a 'lens-based' optical system as well? ...and
refraction provides the bending, focusing and improved resolution as
an 'improvement' on the fundamental effect of the aperture and
diffraction?

Or is diffraction really a minor effect in an optical system using a
large enough aperture to avoid resolution loss from diffraction?

Lastly, regarding the fact that a simple lens and a pinhole aperture
both invert an image, is either diffraction or the Fourier transform
the common factor causing the inversion. (I'm notentirely comfortable
with this question, as the phenomenon existed before the 'name'
Fourier transform became available...and thus may only be a model or
explanation for the phenomenon.

Thanks

Murray Leshner
Holland MI
.

Relevant Pages

  • Re: Diffrection limit for APS-C DSLRs
    ... Diffraction spreads as a linear function of distance ... from aperture to recording media. ... Now project that 1-degree spread onto a surface ...
    (rec.photo.digital)
  • Re: Smaller hole in telescopes cover
    ... As I don't have a telescope, ... The filter doesn't have any edge diffraction effects. ... diffraction limited to the size of the hole, but if multiple holes are used ... I believe that the radio telescopes and Keck use aperture synthesis ...
    (sci.astro.amateur)
  • Re: 20 Years and Still Going
    ... we'd have a very high res, low noise sensor. ... and that is diffraction limiting. ... The higher the pixel resolution, ... has to do with the physical size of the aperture. ...
    (rec.photo.digital)
  • Re: F/0.5 possible?
    ... ASIDE - to perk interest - potential resolution goes DOWN as the aperture decreases. ... So an f/0.5 has more potential resolution than the same stopped to, say, F5.6, but in Real Life lenses are a compromise and usually perform better stopped to the mid-aperture range. ... Below that aperture geometric aberrations are less than diffraction, ... At the optimum f/# the geometric blur circle and diffraction blur circle are equal. ...
    (rec.photo.digital)
  • Re: diffraction curiosity questions
    ... thinking diffraction is responsible for imaging. ... Geometry, ray ... Yet diffraction seems to be responsible for more than just limiting ... propagation is noticeably different from the predictions of the ray model. ...
    (sci.optics)