Archived posting to the Leica Users Group, 2004/03/07

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Subject: Re: [Leica] Re: Crude Film/Digital test, Leica/Canon
From: Jim Laurel <jplaurel@nwlink.com>
Date: Sun, 7 Mar 2004 21:07:52 -0800
References: <5.1.1.6.2.20040307135439.04852278@mail.brick.org>

This may be true if resolution is the only aspect of lens performance 
that you are considering.  But it is only one factor among many in a 
given lens design.  I am by no means an expert on optics, but a key 
differentiator in lenses for me is the control of aberrations and 
distortions.  When I am using my Canon zoom lenses (particularly the 
16-35L and 28-70L), flare from background light is always a big 
problem.  Against the light photography with these lenses is a complete 
waste of time.  Sure, they are very sharp, but they are very prone to 
flare, distortions, chromatic fringing, etc.  The additional resolution 
provided by the Leica lenses may not provide any tangible benefit in 
the digital world, but their superior control of aberrations and 
distortions make a real-world difference.

- --Jim Laurel

On Mar 7, 2004, at 2:24 PM, JCB wrote:

> Many folks still believe that different (good) lenses will exhibit 
> different properties on digital cameras. They won't. Good lenses 
> (Leica, canon, Nikon, Minolta, Zeiss, etc...) will all look alike if 
> used on the same camera. The pixel spacing and interpolation firmware 
> (in the camera) determine the resolution properties of the resulting 
> photograph. Up sizing software (Genuine Fractals, etc.) can make even 
> larger sharp "looking" images. Your good lenses are much much sharper 
> than 6 to 9 micron pixel spacing on a sensor therefore, it's all in 
> the firmware/software which is fooling you into thinking that 
> different lenses on the same digital camera make a difference. They 
> cannot. And the same lenses on different cameras simply point out how 
> good the firmware programmer, for that camera, is.
>
> Digital is not film. Digital cameras have finite spacing on each 
> recorded pixel. Film does not. Silver halide molecules are not only 
> random, but there are billions of them within a 1 cubic micron grain. 
> Lots of opportunities to record light rays. Lots of levels of density 
> available within each one micron, overlapped, silver halide grains. 
> Film is the only medium that can differentiate between film camera 
> lenses. True digital lenses are dumbed down so that their resolution 
> (MTF) is several times less than the 6-9 micron pixel spacing. Digital 
> cameras (SLR's) that take camera lenses have a lens resolution (MTF) 
> spoiling low pass filter mounted over the sensor. Digital sensors are 
> the great lens equalizer.
>
> When testing lenses on digital cameras for sharpness, you are testing 
> the programmer, not the lens.
>
> All of the large prints that you see from ordinary (35mm style) 
> digital cameras is testimony to the software wizards that can write 
> interpolation software to up-size a minimal amount of information and 
> make it look really good. A silk purse out of a sow's ear! Like making 
> a 20x30 print from a 2.7 MP camera. Basically, it's like 
> slight-of-hand. There simply isn't enough information to make a 20x30 
> from 2.7, 3, 5, 6,... MP sensors. Interpolation programmers are 
> magicians. Look up "interpolation" in the dictionary.
>
> You don't have to believe the above. Your prerogative. But it is true, 
> regardless.
>
> JB
>
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In reply to: Message from JCB <jcb@visualimpressions.com> ([Leica] Re: Crude Film/Digital test, Leica/Canon)