Archived posting to the Leica Users Group, 2001/08/10

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Subject: RE: [Leica] Getting film into the film gate in M6
From: "Nguyen, Olivier T [AMSTA-AR-CCF]" <onguyen@pica.army.mil>
Date: Fri, 10 Aug 2001 21:15:43 -0400

thank you for answer my question 
I need a lot of these helpful advice.
thank you again
olivier

- -----Original Message-----
From: Mxsmanic [mailto:mxsmanic@hotmail.com]
Sent: Friday, August 10, 2001 5:20 PM
To: leica-users@mejac.palo-alto.ca.us
Subject: Re: [Leica] Getting film into the film gate in M6


Olivier writes:

> but for this kind of focus, the result is only
> an acceptional of sharpness not perfectly sharp
> please correct me.

You are quite correct, and your concern is very reasonable.

Using zone focusing works _IF_ the final image will be viewed at a "normal"
viewing distance and _IF_ the full frame will be used (no cropping).

However, if you crop the image and enlarge it, or if you view the image from
a
distance closer than the "normal" distance, the depth of field figures used
on
the lens are no longer valid.  DOF drops as you get closer to an image, and
something that looks in focus for a full frame from a normal distance may
look
very blurry when viewed closely or when cropped and enlarged.

This is why it is always best to focus precisely on the subject you actually
want to have in focus, if possible, and if you have time.  The only
exception is
when you have different elements in the image at different distances and you
want them all to be at least moderately well focused--then you have to
compromise.

Nevertheless, for photography that is not critical for sharpness, such as
street
photography and photojournalism, the speed advantage of zone focusing can be
considerable.  I still try to avoid it, myself, as long as I have time to
focus
for real.