Archived posting to the Leica Users Group, 2006/11/01

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Subject: [Leica] M8 & Depth of Field
From: walt at waltjohnson.com (Walt Johnson)
Date: Wed Nov 1 05:59:56 2006
References: <20061101060806.40806.qmail@web37711.mail.mud.yahoo.com>

Lee

I am glad someone finally got to those pesky old circles of confusion. 
They were invented to confuse a whole circle of photographers at one 
time and they do. :-)

Walt

Lee Wai Leong wrote:

>Just to add. I mentioned that the industry had generally used a CoC of 0.03 
>mm for 35 mm lenses.
>   
>  How is this 0.03 mm derived?
>   
>  As mentioned in Wikipedia, using the so-called ?Zeiss formula? the circle 
> of confusion is sometimes calculated as d/1730 where d is the diagonal 
> measure of the original image (the camera format). For full-frame 35 mm 
> format (24 mm ? 36 mm, 43 mm diagonal) this comes out to be 0.024 mm. 
>   
>  A more widely used CoC is d/1500, or 0.029 mm for full-frame 35 mm 
> format, which corresponds to resolving 5 lines per millimeter on a print 
> of 30 cm diagonal. Values of 0.030 mm and 0.033 mm are also common for 
> full-frame 35 mm format. 
>   
>  Since d is smaller for a digital sensor that is less than 24x36 mm, it is 
> clear that a 35 mm lens used with a digital sensor must have a smaller DOF 
> at all distances.
>   
>  Hence, the DOF markings now on our Leica lenses are no longer correct 
> when you put them to use on the M8.
>
> Send instant messages to your online friends http://uk.messenger.yahoo.com 
>
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>  
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In reply to: Message from leewaileong19 at yahoo.com (Lee Wai Leong) ([Leica] M8 & Depth of Field)