[Leica] Leica 21-35mm

[leicaluvr at comcast.net (leicaluvr@comcast.net)]

The retrofocus design with longer back focus length also has the advantage 
of less vignetting, i.e. more even light distribution into the edges and 
corners, at the expense of size and weight. 
Tom 

-------------- Original message -------------- 

> I'm not an expert on it; but I know that film grain has much more 
> tolerance 
> concerning the angle of the incoming light, than sensors usually have. In 
> the centre of the sensor, the light is captured in the ideal 90 degrees 
> angle, but the more you go to the corners, the more this angle is 
> increasing, and the quality too (like a kind of softness-vignetting). 
> 
> 
> The problem occurs with non-retrofocal wide angle lenses more than with 
> retrofocal lenses. The 4/3 system* for instance, and many other digital 
> lens manufacturers, are trying to evitate this problem with new retrofocal 
> lenses. AFAIK, the new Zeiss ZM lenses are built this way, too 
> 
> The disadvantage about this lenses is that they're less compact than the 
> non-retrofocal ones - and the small lenses (compared to SLR) have always 
> been an advantage of rf cameras. 
> 
> Didier 
> 
> * See 
> http://www.four-thirds.org/en/about.html 
> and click Flash or PDF Version. It is explained how the light angle is 
> affecting the sensor. 
> 
> 
> 
> 
> >How does this affect the plane of focus, where the sensor presumably 
> >sits, 
> >especially compared to film? 
> >Frank Filippone 
> >red735i@earthlink.net 
> > 
> >I dont have this lens, but assuming that you did not have this problem on 
> >a 
> >Leica film camera, I think the phenomenon is known. With wide ange 
> >lenses, 
> >the angle of the incoming light to the edges of the sensor is much less 
> >than the ideal 90° degrees. So it might be a sensor problem not a lens 
> >problem. 
> >Didier 
> 
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