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02-01-2013, 02:15 PM   #1
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Infrared Focusing

I used to have a Sony DCS F707 that used infrared illumination to focus in total darkness. It was quite accurate if I recall correctly. My question is: Why canít DSLRs use this technology to do the same? This would solve the low light focusing issues. Iím not up on the technology side of DSLRs, so my question comes purely out of ignorance.

02-01-2013, 02:34 PM   #2
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A P&S has a deep depth of field, so focus errors aren't that pronounced.
The camera would have to be able to correct for every infrared focusing variation, since the focus distance isn't the same in infrared and visible light, due to wavelength differences.
My F 50mm 1.7, for example, has a red mark slightly to the left of the center of the focusing distance window, that is the infrared focusing point.
02-01-2013, 04:57 PM   #3
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Also infrared focusing devices are confused by glass. They focus on the window, not the scene behind it.

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