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11-16-2009, 02:35 AM   #1
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Location: Netherlands
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The benefits of ED glas.

Two very similar pentax lenses, the K 200/2.5, and the A 200/2.8 ED.
Some prefer the K version, but ED pays off :

K 200/2.5 at 2.5


A 200/2.8 at 2.8


These are near center crops of a Paterson optical test target 2, at 25 * f.
Stopping down the K version helps, but at F4 it is still no match for the A at 2.8.
Focussing the K is a nightmare, I can have a sharper red area, but this will end in a blurred green pattern etc.
Off center, the A version shows also a very light purple fringing though.

George

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