[Leica] new Puts article

[henningw at archiphoto.com (Henning Wulff)]

At 6:53 PM -0700 6/27/05, Tom Schofield wrote:
>So, Henning, according to you I will get the same dof shooting the same
>subject at the same distance and aperture with a 50mm on 35mm film as with
>an 80mm on 6x6?

Nope. It's more complicated than that. I'm just saying that if you 
use a 50mm lens, your final print size is the same and your CoC 
criteria are the same for both prints, then the print made from a 
sensor/film that is smaller will require more stringent DoF decisions 
when taking the picture.

>All of the confusion that creeps up when people talk about dof varying with
>distance, focal length or format loses sight of the basic rule:  At the same
>aperture and subject distance, dof remains the same as long as the
>magnification ratio remains the same, i.e. dof remains the same so long as
>image size at the focal plane remains the same.

... and the circle of confusion criteria remain the same.

>Since image size at the film plane is smaller with smaller formats, i.e.
>magnification ratio is smaller, dof is deeper.  (That's why a fixed focus
>Minox 15mm 5.6 goes from 1m to infinity).  With larger formats, image size
>at the focal plane is larger, i.e. magnification ratio is greater, so dof is
>shallower.  (Again, assuming the same aperture and distance.)
>
>Erwin is saying a smaller sensor is like a smaller format -- lower
>magnification ratio, hence deeper dof at the same aperture and distance.  I
>agree with him.

Certainly. It's just that 'a 50 is a 50' doesn't play for different 
formats, as CoC criteria differ.

I guess you were responding to my other post.

>Tom Schofield
>
>-----Original Message-----
>From: lug-bounces+leicaluvr=comcast.net@leica-users.org
>[mailto:lug-bounces+leicaluvr=comcast.net@leica-users.org] On Behalf Of
>Henning Wulff
>Sent: Monday, June 27, 2005 10:45 AM
>To: Leica Users Group
>Subject: Re: [Leica] new Puts article
>
>At 3:34 AM +0200 6/25/05, animal wrote:
>>http://www.imx.nl/photosite/comments/c014.html
>
>An awful lot of sloppy/illogical thinking. Hardly any of his
>conclusions or statements bear careful analysis.
>
>The thing I agree with, though, is that the M lenses and mount are
>unsuitable for full frame digital use as I have contended for years,
>for all the reasons expressed previously. Erwin seems to try to work
>backwards from this position, and force various other concepts which
>are not necessarily relevant to support the result.
>
>Hard to tell what the point of the article is.
>
>--
>     *            Henning J. Wulff
>    /|\      Wulff Photography & Design
>   /###\   mailto:henningw@archiphoto.com
>   |[ ]|     http://www.archiphoto.com
>
>_______________________________________________
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>
>
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-- 
    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  /###\   mailto:henningw@archiphoto.com
  |[ ]|     http://www.archiphoto.com