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Sigma highlights another problem with plastics, thermal change



 
 
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  #1  
Old June 19th 12, 12:22 AM posted to rec.photo.digital.slr-systems
Me
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Posts: 241
Default Sigma highlights another problem with plastics, thermal change

On 17/06/2012 3:44 a.m., RichA wrote:
Heat expansion and contraction, which effects optical performance. So
they've introduced something else to compensate for it. Because
aluminum and magnesium don't suffer nearly as much thermally-related
shape changes as plastic, older lenses and new high-end principally
metal lenses do not have the problem.

http://www.dpreview.com/news/2012/06...superzoom-lens


Thom Hogan sums it up nicely in his website:

"Of course, if they didn't use black they might not absorb so much heat
in the first place"

  #2  
Old June 19th 12, 08:24 PM posted to rec.photo.digital.slr-systems
Alan Browne
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Posts: 12,640
Default Sigma highlights another problem with plastics, thermal change

On 2012-06-18 19:22 , Me wrote:

http://www.dpreview.com/news/2012/06...superzoom-lens



Thom Hogan sums it up nicely in his website:

"Of course, if they didn't use black they might not absorb so much heat
in the first place"


This goes back to a discussion (in rpe35mm) from long ago.

Large lenses should be white.

OTOH, Nikon don't seem to agree and we don't hear much of the issue with
their lenses.

--
"Civilization is the limitless multiplication of unnecessary necessities."
-Samuel Clemens.
 




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