Archived posting to the Leica Users Group, 2010/11/25

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Subject: [Leica] 6bit coding
From: red735i at earthlink.net (Frank Filippone)
Date: Thu, 25 Nov 2010 21:33:55 -0800
References: <mailman.414.1287534906.1032.lug@leica-users.org> <4CBE4957.1090303@verizon.net> <4CEE8BFA.8000808@mcclary.net> <04e701cb8ccf$938be950$baa3bbf0$@earthlink.net> <EBF386F3-8BEF-4A30-BC3F-3DAC2625247B@btinternet.com>

I agree, however DOF of a 21mm covers up inaccuracy in focusing.....which is
essentially what a too thick or too thin mount would do to/for you.....

I do not understand why " mount precision gets greater with wide angle
lenses, not less, since a given axial error is a bigger proportion of the
focus travel."

Can you explain to me ?  

Frank Filippone
Red735i at earthlink.net


-----Original Message-----
From: lug-bounces+red735i=earthlink.net at leica-users.org
[mailto:lug-bounces+red735i=earthlink.net at leica-users.org] On Behalf Of
Frank Dernie
Sent: Thursday, November 25, 2010 12:18 PM
To: Leica Users Group
Subject: Re: [Leica] 6bit coding

Hi Frank,
it is not the depth of field which is important for the focussing register,
but the focussing travel. The importance of mount precision gets greater
with wide angle lenses, not less, since a given axial error is a bigger
proportion of the focus travel.
I am sure someone on the list has the data but IIRC the axial focus travel
for a given change in distance is proportional to the focal length, so a
21mm is about 2.5 times -more- sensitive to an axial error than a 50mm lens.
cheers,
FD

On 25 Nov, 2010, at 18:35, Frank Filippone wrote:

> It made no difference to my 21.... but then again, my DOF is a "bit" 
> more relaxed.....


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Replies: Reply from Frank.Dernie at btinternet.com (Frank Dernie) ([Leica] 6bit coding)
In reply to: Message from lists at mcclary.net (Harrison McClary) ([Leica] 6bit coding)
Message from red735i at earthlink.net (Frank Filippone) ([Leica] 6bit coding)
Message from Frank.Dernie at btinternet.com (Frank Dernie) ([Leica] 6bit coding)