In fact, many high performance designs start to degrade even at f/8, which
is usually the sweet spot for most lenses. I speak particularly of Leica
lenses, which are usually best between f/4 and f/8.
Also, in general the longer the focal length, the smaller the minimum
aperture can be. Is that because of the more telecentric light rays?
Anyone? This is evidenced by Large Format lenses for 4x5, which routinely
go to f/45, and 8x10 or 11x14 lenses, which can go to f/128.
Skip
Original Message:
-----------------
From: Winsor Crosby wincros@xxxxxxxxxxx
Date: Tue, 07 Jun 2005 13:16:03 -0700
To: olympus@xxxxxxxxxx
Subject: [OM] Re: Apertures, where is f22 ?
In lenses for the 35mm film format you start running into significant
softening of the image by F16 due to diffraction effects of the
physical size of the aperture. It just gets worse at F22. In smaller
format digital cameras the cutoff is frequently before F8, for the
same reason. The newer Sony digital cameras have been roundly
criticized because their exposure program goes immediately to a small
F stop and has soft images as a result. I think leaving it off is
just a recognition that knowledgeable photographers, who seem to be
the only people still using lenses with F markings, just don't use
F22 because of image quality issues.
Just for your own information you could check out the lens tests at
Gary Reese's web site and see the resolution start to drop at F16 in
lens after lens.
Winsor
Long Beach, California, USA
On Jun 7, 2005, at 12:53 PM, Der Eiserne Reiter wrote:
> List,
>
> let me offer a new technical subject:
>
> I have often wondered why some lenses in the 28-50mm focal range do
> not offer an additional f stop. I understand that is is technically
> difficult to provide both wide and small apertures, and good bokeh,
> but for landscape photography, f22 is very helpful sometimes.
>
> Why do some lenses stop at f16 and others continue to f22 ? Do other
> people care about f22 ? For instance, the 50/3.5 features f22, while
> the 1.2, 1.4, 1.8 do not. Technically it is feasible to get f22 with
> a wider lens, as was demonstrated by C*non in the 50s with their
> 50/1.2 lens. Why do the 35/2.8, 28/3.5 and 28/2 not have f22 ?
>
> Just wondering,
>
> Roland.
>
> PS: forgive my English, it's my third language. As our Kahlifonian
> governor says:
> Q: isn't my English very good - A: yes it isn't ...
>
>
>
>
> FeRider (R.)
>
>
>
> __________________________________
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