It depends on your standard of sharpness. Within the markings, it will be
sharpest at the exact point of focus, deteriorating as you move away.
Lenses can be designed to have more depth of field by sacrificing sharpness at
the exact point of focus, sort of spreading out the focus area. I imagine that
the next-to-cheapest "focus-free" cameras have lenses designed this way. (The
cheapest use even more basic designs...)
> Date: Tue, 04 May 1999 16:50:26 -0700
> From: "George M. Anderson" <george@xxxxxxxxxxxxxxxxxx>
> Subject: Re: Infinity and F-stop RE: [OM] Monopod & ball head
>
> They're just approximations. How accurate can you really read the thing
> anyway? Course, you can always see the effect by slowly stopping down the
> depth of field button. When in doubt, I always focus on the nearest
> object I want in focus, note the distance on the scale, then focus on the
> farthest, note that distance and see what f stop is needed to include
> both. Sometimes, you'll find you're asking too much of the lens and will
> have to settle for less (or switch to a wider lens). Lastly, note that I
> said 'acceptable' focus. As objects approach the near and far limits,
> they will go slightly soft. The acceptableness is determined by circles of
> confusion, print size and viewing distance, etc etc. Too much for here.
>
> George
>
> "Barry B. Bean" wrote:
> >
> > On Tue, 04 May 1999 11:09:15 -0700, George M. Anderson wrote:
> >
> > >Look at the focus ring and the lens flange. The flange has F/#s on it,
> > >focus ring distances. If you focus on infinity, there will be some
> > >distance in the foregroud after which objects out to infinity will be
> > >in focus. Eg: Zuiko 50/1.8: when focussed to infinity with lens
> > >aperture set at F/8, acceptable focus is from 10m to infinity. But if
> > >aperture is set to F/16, the close limit moves to 5m. But, look what
> > >happens if you set the focus to 10m and aper to F/8. Now the flange
> > >marks indicate acceptable focus from 5m to infinity, same as F/16
> > >above! Very useful to use this method for max depthe of field. Method
> > >is called 'hyperfocal.'
> >
> > Just how accurate are lens markings? I notice that on my 200/5 that the
> > hyperfocal distance at f16 looks to be 150yds judging by the lens
> > markings. But according to the hyperfocal calculator at
> > http://www.frii.com/~mbaltuch/HyperFocal.html, the hyperfocal distance
> > for f16 should be 83.33 yards. Which should I trust?
> >
> > BB
> > -
> > B.B. Bean - Have horn, will travel
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