AF working range/detection range?

Started Sep 4, 2004 | Discussions thread
gisle
Senior MemberPosts: 2,468
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Re: AF working range/detection range?
In reply to Carl Snyder, Sep 5, 2004

Carl Snyder wrote:

What determines a camera's ability to focus in low light? I
noticed that the 20D has a rating of -0.5 to 18, while the 1DII is
rated at 0 to 18. The detection range of the nikon cameras is -1
to 19. What do these numbers mean and what determines them?

These are EV numbers and they are a convienent way to indicate absolute light levels without going into ISO, apertures and shutter speeds.

EV 0 to -1 are "subjects lit by dim ambient artificial light", according to Fred Parker's EV chart: http://www.fredparker.com/ultexp1.htm .

There is a good explanation ov EV in the dpreview glossary, under "Exposure": http://www.dpreview.com/learn/?/Glossary/Exposure/Exposure_01.htm

There is a somewhat simpler intro to EV at my IR resource page: http://heim.ifi.uio.no/~gisle/photo/ir.html#ev
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  • gisle

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