On Sun, 11 Mar 2001 09:29:05 -0500, "Doug Graham" wrote:

>There's been a lot of discussion on the TRV900 mailing list lately about
>lens sharpness at high f stops. It turns out that any lens becomes less
>sharp in this situation, and the smaller the lens and imaging area, the more
>severe the effect is. The 900, with its small lens and 1/4" CCDs, is
>particularly vulnerable. The cure is to use the internal and an external ND
>filter to get the iris setting to f/5.6 or less.

Hmmmmmm........;-)
There is always a lot of misconception about this, and
being a sharpness nut, I do pay attention to optimum stops
for particular lenses - but.....
The TRV-900 lens is a good, but not great lens (it is
noticeably softer (with color-fringing, also) at wide stops,
which shows even in this lens-forgiving, low-res. medium).
What follows is that there will likely be an optimum stop
between the improving image quality to be had from stopping
down a so-so lens, and the unimproving image quality to
be had from diffraction from stopping down too far
(decentered elements will also tend to spoil resolution
with excessive stopping down), but this optimum stop may
also change with FL selected and focus point, making the
selection of optimum stop complex (and different again
with a lens converter added). And, the TRV-900 lens is
limited to a smallest stop of f11 (well into diffraction
limiting with a great lens, but otherwise...), not a bad
stop at all to use - I have seen f32 selected on my PC-1
in auto mode, with images that were still sharp-looking
(though in 35mm photography, one would NEVER use f32
if the interest is in a sharp image...;-). This medium
is forgiving of optical flaws, so except for trying to
avoid using the widest stop(s), I wouldn't worry much
about one that is too small...