Yes, as I said on the web page, it is not surprising that
diffraction is a "non-issue" with video due to the
medium's low-resolution, but it is useful to show that
it isn't an issue, since people sometimes believe it is...
As for 35mm macro work, I still don't know why, but with
some combinations of lenses, achromats, and particularly
rear lens converters, it does appear possible to "cheat"
the diffraction limits and use about f45 effective aperture
and still get "wirey" results... These are small jpgs, so
not necessarily convincing (the originals are QUITE sharp,
and these insects are QUITE small, though, and the DOF is
greater than one might expect for the sharpness and
magnification...). The general insect series is at:
www.David-Ruether-Photography.com/phun.html
but for high-magnification, look especially at the first two, at:
www.David-Ruether-Photography.com/web_photos/phun_fotoz/bugs/b55.jpg
www.David-Ruether-Photography.com/web_photos/phun_fotoz/bugs/b57.jpg
www.David-Ruether-Photography.com/web_photos/phun_fotoz/bugs/b61.jpg
BTW, these were all shot "in place", unstaged, and "hand-held", with flash...

On Mon, 01 Apr 2002 00:45:28 GMT, "Gary Reif" wrote:

>Hey this is one topic I love to chime in on! I did a lot of work with
>lenses, resolution test charts, in the past and a few comments come to mind:
>-Only real expensive lenses get close to being diffraction limited at any
>aperture bigger than f5.6 or f8.

This is true, for 35mm. For smaller formats, the f-stop
moves wider (and you can see in the VX2000 examples
a slight peaking in performance around f4 - but not enough
to worry about...;-); for larger formats, the optimum stop for
resolution generally moves smaller...

>-Film grain for hi res films is down around 2 microns and smaller, so until
>the photosensor elements get that small, there won't be much problem or
>effect. (ex; a 5 micron pixel will be a 10 micron pitch (which is how
>resolution is measured, in cycles per mm), so that is 100 c/mm)).
>- Resolution of a lens gets down to 80-100 c/mm in the range of f16 , f22,
>or f32 (ok I pulled my ref book off the shelf, the actual numbers are 93
>c/mm at f16, 68 c/mm at f22, and 47 c/mm at f32; these are at 546nm
>(green) and represent a threshold contrast of approx 15% (to "just discern
>the bar and the space)).
>-This can be a big problem for macro work or enlargements, because the
>effective f number is very high due to the magnification and can ruin the
>sharpness.
>Any more questions I have lots more info!!!
>Gary

Thanks for the info.

>"Neuman - Ruether" wrote in message
>news:3ca7958d.27276118@newsstand.cit.cornell.edu...
>>
>> The question comes up every once in a while
>> about optimum apertures for video, and the
>> effects on diffraction on image sharpness
>> when small stops are used. I decided to
>> check this out, and put the results on
>> my web page, at:
>> www.David-Ruether-Photography.com/diffraction.htm
>> Bottom line: for Mini-DV, don't worry
>> about the resolution-limiting effects
>> of diffraction...
>> David Ruether