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Old 11-08-2012, 05:53 PM
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theodog (Jeff)
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Join Date: Oct 2007
Location: Coonabarabran
Posts: 1,037
F-Ratio's and APS-C Imagers

Hi All,

My question concerns the effective f.number for the APS-C chips. I know that the effective focal length of a lens will change (usually by 1.5 or 6). So a 10mm on full (35mm) frame is effectively 15mm on a APS-C, but how does this effect the f ratio? And is there a simple way of calculating this?
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