> On Feb 22, 2017, at 12:36 PM, Mark Roberts <postmas...@robertstech.com> wrote:
> 
> John wrote:
> 
>> Or else Google translate just has a dirty mind.
>> 
>> What I need explained is why new lenses are so much longer than the old
>> ones of the same focal length?
> 
> Every lens design is the result of many compromises: Small vs. large,
> expensive vs. cheap, tack-sharp vs. just-sharp-enough. As sensor
> resolution (and pixel peeping) increase it pushes lens designers
> towards ever more demanding optical requirements and something has to
> give — in this case it's size/weight. So we gain optical resolution
> and lose light weight and compactness. Reducing light falloff in the
> corners generally requires larger diameter lenses and in the age of
> pixel-peeping people are more critical of that than ever (which is odd
> because it's easier than ever to correct in post).
> 
> -- 
> Mark Roberts - Photography & Multimedia
> www.robertstech.com
> 

I wonder about one other factor - with internal focus the external lens will be 
longer to accommodate the (internal) movement of the focusing elements. Yes?

stan
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