Why is the body open?

Started Feb 9, 2013 | Questions thread
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Regular MemberPosts: 441
glass/air surfaces are bad for your image health...
In reply to Rexel99, Feb 11, 2013

Rexel99 wrote:

Surely a piece of glass could be in that hole, in front of the mirror (behind the lens) to prevent dust getting in.

Because two more glass/air surfaces would further reduce the optical quality of any lens used with the camera. Lens designers are doing their utmost to keep the number of air-glass surfaces to the minimum possible: sometimes two glass elements of a lens are glued together just that exact reason. Old Tessar lens design was an early example: it was better than any similar 4-element lens mostly because the two rear elements were glued together (at that time, using something called "Canadian Balsam". Today they use Canadian Club).


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