Archived posting to the Leica Users Group, 2003/01/14

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Subject: RE: [Leica] I eat crow
From: "Austin Franklin" <darkroom@ix.netcom.com>
Date: Tue, 14 Jan 2003 14:50:50 -0500

> I retract my questioning of Martin Tai's calculation.  I was thinking
> in terms of the image space instead of the object space.  While
> mulling over this while eating breakfast, I realized my error.  I
> calculated the correction assuming that the 50mm lens is a thin lens
> since I don't know the distance between the image and object
> principal planes of a Leica 50mm Summitar, e.g.  I came up with a
> setting of 94.61 cm, which is pretty close to Martin Tai's 94.7.

Herb,

The amount of deflection is SOLELY based on where the pivot point is, and
obviously different pivot points will vary the distance.

If the pivot point is the middle of your body (such that you take the
camera, in your hands, and turn your entire upper body), then yes, you can
get a substantial deflection...but it's up to YOU to control that.  If you
simply "adjust" the camera by turning it in your hands, you will get a very
small deflection, well under 1/2".

This "issue" is obviously technique dependant, but I must admit, I have
never had this be an issue, and I shoot wide open all the time, and do
"re-focus" for quite a few shots...focus is spot on for me.  No "calculated
adjustments" required.

I'd suggest anyone who is questioning whether this "methodology" is of any
use for them, to simply do the experiment them selves.  Shoot some with, and
some without.

Regards,

Austin

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