Answers/comments interspersed:
Thanks,
Ed
----- Original Message -----
From: "Shel Belinkoff" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, February 17, 2001 12:07 PM
Subject: Re: Autofocus Question
> Ed Mathews wrote:
>
> Hi Ed ...
>
> > AF is not for everything, especially
> > for us people shooters. I prefer to
> > use it as a feature I resort to when
> > manual focus is difficult
>
> What MF bodies are you using?
Well, I've owned a LOT of cameras. Right now, my manual focus cameras are a
Pentax Super Program and a Nikon F3HP.
The LX (and, I suppose, the MX to
> a degree) with its interchangeable screens seems to work well
> for me, as the lens can be matched with the screen. I've pretty
> much stopped using the ME S because there's but one screen, and
> it doesn't work well for all lenses.
The SP and the F3 both provide an unobstructed view of the screen which is
why I own them. I prefer the higher eyepoint of the F3 most of the time,
and I have replaced the standard screen with the focusing aids with one
which has no aids at all, and just ground glass. So with the higher
eyepoint and just ground glass, it's perfect for composition with all
lenses - never darkens appreciably or blacks out under any circumstances.
But the magnification is not high, so sometimes critical focus is not easy.
The SP has higher magnification, and lower eyepoint - but I can still use it
well, even with glasses. If I could, I would probably still prefer no
focusing aids though. Sadly, not possible with that camera.
>
> > many of the smaller center zone
> > AF brackets in cameras are very
> > adequate at being able to focus
> > on an eyeball, another problem
> > lies in that you seldom place
> > the eyeball in the middle of the
> > frame, so you need to recompose after
> > focusing.
>
> Depending on various factors, one can get acceptable results (at
> lest with MF gear - not tried this with AF equipment) by
> focusing on something other than the eye. Mafud noted that it's
> best to focus slightly behind the eye in order to be sure the
> eyes are sharp.
I'm not sure I get this. DOF is 2/3 BEHIND the plane of focus, only 1/3 in
front. Why focus behind something?
That seems so obvious now that he's mentioned
> it, but I've never thought about that before. Definitely
> something to try.
>
> > 1) You might find it ounter-intuitive
> > to focus and then compose, as opposed
> > to focusing WHILE you compose;
> > 2) Your focus then is locked after you
> > recompose, and so if your subject or
> > camera moves just a little, then you
> > have to go through the whole process again;
>
> Yes, sometimes that's a PITA, although, as you know, being aware
> of DOF and your shooting aperture can be helpful in those
> situations. But it is sometimes frustrating, especially if
> you're trying for a very specific final result, and precusion is
> important.
>
>
> 3) Even if your subject and camera
> > remain in perfect position, the
> > differences in the lens field of
> > flatness can often make the focus
> > point you achieved in the center of
> > the viewfinder wrong to begin with,
> > especially when close to the subject
> > an/or using very limited DOF.
>
> That's something I've not considered before. Thanks for giving
> me something more to think about while focusing <g>.
Glad I could complicate your life, and take even some more fun out of the
process for you. :)
>
> > It's amazing how different the
> > true plane of focus can be at
> > close distances on axis vs.
> > slightly off axis for all but
> > macro lenses.
>
> You've answered what would have been my next question. What
> you're suggesting then is that using a macro lens for some
> portarit and people shots, like one of the Pentax 100mm lenses,
> might allow for better focus accuracy in certain situations.
> Very interesting, and it makes absolute sense.
Yeah, for focus accuracy, a macro lens should provide better flatness of
field and be better. But then you get all those nasty macro problems, like:
too sharp; not such great bokeh; slower lens, etc....
>
> > And in the ZX5N (besides not being
> > able to choose the AF sensor), the
> > outer AF brackets are only sensitive
> > to horizontal lines so in the portrait
> > position, they don't see the eyeball well.
>
> That's good to know. Since the MZ-3 is essentially a 5n, I
> suppose the AF is the same for both cameras. I'd been thinking
> about a '3, but will now wait to see what the MZ-S is like.
That's a good idea. The 5N and 3 are getting old in their class, and I've
never been much impressed with my 5N's AF. The latest issue of Practical
Photography compares the 3 and three other cameras in that class from the
other guys, and the Pentax finishes last, with the usual complaints of
outdated technology. They even mention the darker, dimmer viewfinder.
>
> > Thanks,
> > Ed
>
One other note, Shel (and others). I have a Popular Photography article
that I scanned from a while back that compares manual focus and autofocus
accuracy. Bottom line is that AF works about as well as most people can do
manually under normal shooting conditions. But in critical conditions, in
every case with every lens and camera used, AF failed to provide enough
accuracy to match a carefully manually focused lens when comparing them with
lines/mm tests. Sometimes the results were staggering. I'll e-mail you (or
anyone) that if you wish, but it's 9 big jpgs, and I'm only sending it once,
so let me know.
> Thank ~you~!
>
> --
> Shel Belinkoff
> mailto:[EMAIL PROTECTED]
> -
> This message is from the Pentax-Discuss Mail List. To unsubscribe,
> go to http://www.pdml.net and follow the directions. Don't forget to
> visit the Pentax Users' Gallery at http://pug.komkon.org .
>
>
-
This message is from the Pentax-Discuss Mail List. To unsubscribe,
go to http://www.pdml.net and follow the directions. Don't forget to
visit the Pentax Users' Gallery at http://pug.komkon.org .
