Hi,
> Shel, Bob...the depth of field scale does not indicate the lens'
> sharpest aperture; it merely tells you hyperfocal info. The MTF program
> does NOT use hyperfocus, it uses the lens' sharpest apertures whenever
> possible. For instance, if a given lens was okay at f2, good at f4,
> amazing at 5.6, good at f8, and okay at f11, the camera would try to use
> f5.6 if the lighting conditions allowed, and otherwise move to f4 or f8,
> and only use f2 and f11 if there were no other choice. I don't see a
> method of achieving this anywhere on the hyperfocal scales of any of my
> lenses.
every f-stop has a hyperfocal distance. The reason why one of them,
generally f/8, is marked differently from say f/11 or f/16, both of
which will of course give you greater depth-of-field and are therefore
better from the hyperfocal point-of-view, is that f/8 is the optimal
aperture from the optical quality pov. So it was quick and easy to get
the optimal combination of aperture and depth-of-field for hyperfocal
distance. It is also why the phrase 'f/8 and be there' specifies f/8
rather than f/64 or whatever. If it was just about getting as much in
focus as possible they'd all do it with the smallest aperture.
According to my information ("Pentax users guide Z1 etc." by John
Clements, Hove Books), which may be wrong, the MTF programme "selects,
when it can, the optimum aperture for the lens in use and adjusts the
shutter speed to match. [...] If the need arises in order to capture the
shot, the aperture will be adjusted away from the optimum aperture.".
It says nothing about chossing apertures in descending order of MTF optimality.
As I said originally, this method is achievable on older lenses which have the
optimum aperture marked; if you're not happy with the shutter speed that follows
from the optimum aperture then you can just change the aperture +/- one click.
Even though the marked aperture also lines up with its marked hyperfocal distance,
you are not obliged to set the focus to the hyperfocal distance.
---
Bob
mailto:[EMAIL PROTECTED]
Monday, March 04, 2002, 6:35:21 PM, you wrote:
> Bob wrote:
>> I've always thought of this as a classic example of pointless
>> automation. On the older series of prime lenses the optimal aperture
>> was marked in a different colour from the others. In conjunction with
>> the depth-of-field scale on the lens this did everything that the MTF
>> programme does, and all it requires is paint and a fine brush. A nice
>> simple
>> solution.
> Shel replied
>> I agree with Bob .... a waste of electrons!
> Shel, Bob...the depth of field scale does not indicate the lens'
> sharpest aperture; it merely tells you hyperfocal info. The MTF program
> does NOT use hyperfocus, it uses the lens' sharpest apertures whenever
> possible. For instance, if a given lens was okay at f2, good at f4,
> amazing at 5.6, good at f8, and okay at f11, the camera would try to use
> f5.6 if the lighting conditions allowed, and otherwise move to f4 or f8,
> and only use f2 and f11 if there were no other choice. I don't see a
> method of achieving this anywhere on the hyperfocal scales of any of my
> lenses.
> -Aaron
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