Archived posting to the Leica Users Group, 2004/03/02

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Subject: Re: [Leica] Leica M and Cosina Digitals
From: "Jacques Bilinski" <jbilin@axionet.com>
Date: Tue, 2 Mar 2004 10:59:34 -0800
References: <00f801c4006d$02f80360$6401a8c0@CCA4A5EF37E11E> <2147483647.1078214225@hindolveston.reid.org>

> This is just a mind trick. Don't think of it as magnification, think of it
as cropping. A lens is a lens, and it behaves the same whether it is imaging
onto film or a digital sensor. Its depth of field is whatever it is.
>
> But if you are imaging onto a digital sensor, that sensor is smaller than
film, which gives you a mandatory crop of your image: the outer parts simply
aren't there.
>
> Given that your image has been cropped for you by the camera, you now must
magnify it in order to produce one that is the same size that you would have
gotten if you had been using film. It is this enlargement, and not some
magic trick inside the camera, that modifies the image. And it works in
EXACTLY the same way that the same lens would work on film if you did that
amount of enlargement to the film.
>

Everything you said is true, but what you did not say is that when you
magnify an image you reduce the aparent depth of field, and when you are
shooting on a small sensor there will be more of a need to magnify the
negative to produce the same size print.

The magnification factor used to convert focal lengths (eg 1.5) can also
used to convert the f stop. So a 35mm lens F2 lens on a small sensor digital
will produce the same image on a 4 by 6 print or a computer terminal as a
52.5mm F3.0 lens. The net effect is that if you really like out of focus
backgrounds they are not as easy to obtain with the small sensor digitals.


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In reply to: Message from "B. D. Colen" <bdcolen@earthlink.net> (RE: [Leica] Leica M and Cosina Digitals)
Message from Brian Reid <reid@mejac.palo-alto.ca.us> (RE: [Leica] Leica M and Cosina Digitals)