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Forum: Pentax SLR Lens Discussion
06-10-2011, 08:47 AM
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 Quote: Originally posted by newarts
With the advent of faster sensors the need for faster glass is moderated quite a bit.
...... I certainly agree, but the K-x's ISO improvement over my K100D made my DA 55-300mm lens practical for indoor sports, nighttime sports, theater, birds in the forest, etc. This was a huge practical gain for me and might be for many people.
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Forum: Pentax SLR Lens Discussion
06-08-2011, 08:13 AM
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With the advent of faster sensors the need for faster glass is moderated quite a bit.
Cutting F-number by half is equivalent to quadrupling ISO; I think there is at least another factor of two available for ISO improvement.
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Forum: Pentax SLR Lens Discussion
06-06-2011, 08:19 AM
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Doesn't the short registry distance give rise to image circle problems? I guess the answer is likely no for long focal lengths but why then does the shorter registry distance matter?
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Forum: Pentax SLR Lens Discussion
06-04-2011, 09:00 AM
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As a first approximation long fast lenses should be really really cheap because as the focal length gets longer and longer the lens curvature gets flatter and flatter.
In the limit of infinite focal length the lens is a simple flat plate which can be very thin so contains no glass at all.
The cost devil is in the details :)
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