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09-02-2010, 12:18 AM   #1
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Pentax 50-135mm SDM DA* F2.8 w/ kenko x2 converter

Hi there

Just a question. I have added this lens to my K20D with a Kenko x2 converter.

The camera only pics up the focal length at 135mm and not 270mm as it should be with a x2 converter.

I have set the camera at Av priority, F8. Because the camera can only read focal length 135mm instead of 270mm, is my F-stop F8 or F16 now? Fotos taken shows quite a lot of depth of field...



09-02-2010, 12:30 PM   #2
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You lose two effective stops with a 2x TC, so when your lens is at F8, the effective aperture is indeed F16. The DOF will be greater, but the effect isn't that dramatic due to the increased focal length.

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09-02-2010, 09:47 PM   #3
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Thanks for the info, make sense!

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