Re: Konica IR ...!st time, hyperfocal focusing, and Stigmata

["Christina Z. Anderson" <tracez@xxxxxxx>]

OK OK, I'm too lazy to go lug out my textbook so I'll just ask this
question:  I have heard the sharpest aperture on a lens is 2 stops down from
smallest, i.e. an F32 lens is sharpest at F16.  You are saying that
diffraction is worse at smaller apertures/higher F numbers?  And with
infrared film this problem is accentuated?  Thus, what aperture would be
best for shooting infrared?  I always assumed that the smaller the aperture
the greater the depth of field (which, as you say, is exactly what I was
doing with the hyperfocal focussing) which would in turn give me a greater
chance of having a sharper image throughout.  At some point there must be a
tradeoff/crossover between the two--depth of field vs diffraction, no?
Chris Anderson>
> The other problem may be aperture.  Using f/32 (from memory) on 35mm
> renders the entire image so soft that it is _just_ acceptably sharp
> ("acceptably" means approx 0.25mm of fuzz on sharp edges in an 8x10
> print).
> > But with IR, the problem of diffraction is far worse so f/22 could
> easily cause the same problem with IR.
> Thus the overall lack of sharpness could simply reflect a too small
> aperture used.  This is especially true if the smallest aperture was
> used to gain the closest hyperfocal distance.
> Steve


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