Archived posting to the Leica Users Group, 2003/03/15

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Subject: RE: [Leica] Latest shot from a digital with a Leica lens
From: "Austin Franklin" <darkroom@ix.netcom.com>
Date: Sun, 16 Mar 2003 02:36:47 -0500

Hi Robert,

> From my experience, the digital seems to be even more critical of lens
> performance.  My guess would be better lenses create smaller circles of
> confusion and hit the pixels in the sensors more directly, rather than a
> wider circle and hit more pixels, that then have to be interpolated.

Not really.  The MTF of any of any decent lense is well above that of the
digital sensors used in the high end 35mm-esque digital cameras.  Take the
Kodak 14N.  It has a full frame sensor of 4560 x 3048, which is 4560 over a
36mm span, or a sensor element size of 7.9u (microns) square (36/4560).

That would be an MTF of around 63 lp/mm (1000 times 1/7.9 divided by 2, the
2 is for line pair), well below what most lenses are capable of, though
typically better than you can do handheld.  You'll get between that and half
that in reality because of how sampling works, so max is 63, and worst is 32
lp/mm, and that doesn't take into account any effects of the Bayer pattern
sensor and it's processing that is required.

Now, decent films have an MTF up around 120 lp/mm, so film still have the
resolution edge on the highest end 35mm-esque digital SLR at this point in
time, and realistically, I'm not sure the resolution of these digicams is
going to get much higher very soon, nor does it really need to for most
applications.

Point is, digital isn't really any more sensitive to good lenses than film
is, in fact, it really is less sensitive.  But, you will notice the
difference, certainly, between mediocre lenses and good lenses with any D-60
or above resolution digicam.

Regards,

Austin

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