On Mon, 23 Nov 1998 12:28:34 -0800, no.spam.badamson@ix.netcom.com (B. Adamson) wrote:
>In article <365a77bf.5455140@newsstand.cit.cornell.edu>,
>ruether@fcinet.com wrote:
>>On Sat, 21 Nov 1998 10:29:35 -0800, "vonohlen"
>> wrote:

>>>Some lens are "sharper" at or close to their maximum aperture. You actually
>>>can get a degradation of quality shooting at f11. The most difficult thing
>>>that I am relearning is to shoot more with the lens at or near wide open. (I
>>>was trained on TLRs and Speed Graphics ;-)

>>Hmmm, I have checked a LOT of lenses (including many of Nikon's
>>best...), and the above has not been my experience... Virtually
>>all good lenses for the 35mm format peak at f5.6-f8 in the
>>center (but the corners may peak anywhere from around f5.6 to
>>minimum aperture, depending on lens type).

>My understanding is that lenses are generally sharpest at about 2 stops
>from wide open. Thus it is not a specific aperture, but depends on the
>lens' maximum aperture. I suspect you see reference to f/8 or f/11
>because so many modern (or less expensive) lenses have maximum apertures
>of f/4.5 or f5.6 (especially zooms). f/11 would be two stops down from
>f/5.6.

UMMMM!!! (Sorry for my annoyance, but it is exactly this worthless
rule-of-thumb that is incorrect!) It doesn't work, since, as I
and many others find, REGARDLESS OF LENS SPEED, optimum
sharpness in the center for virtually all good lenses for the 35mm
format peaks around f5.6 to f8. Period! It is also a very simple rule of
thumb to remember. Go away, "2-stops down" ROT! ;-) "F8 is best"
rules! ;-) But, seriously, as I pointed out in my original post,
I have checked one LOT of lenses (see my Nikkor evaluation list,
on my web page under "I babble" for an idea how many [though this
list doesn't include a large number of other-brand lenses that
I have also checked...]), and the "2-stop" ROT simply doesn't hold
water...;-). If you don't believe it, take any of your better
lenses, and check it out: shoot a careful set-up (preferably
with subject matter with some depth to it, and which is not
near minimum focus. Use MF and ME, with no changes between
frames except a change of f-stop (with the shutter speed changed
to keep the exposure constant). Run through the aperture range.
Use slow slide film, in good (and constant) light. Check the
results with a good 8-10X magnifier. Let us know what you
find...