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Old February 12th, 2006, 08:18 AM   #1
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How many stops of latitude does the eye have at a time.

I am curious, what range of stops of latitude does the human eye have at any one time?

I know people say number between 15 and 20 stops, but is that including your eyes iris fully open and fully closed, and night vision, or is at some particular iris size?

A medium grade camera might get 8 stops, but stepping down it's iris or adjusting the gain allows that window of latitude to work over a much wider range.

Thanks

Wayne.
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Old February 18th, 2006, 11:11 AM   #2
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John Jackman has a well done book called Lighting for Digital Video and Television.

He does a good job of explaining why our TV lighting has to use lighting techniques to create 3d objects on a 2d screen.

In chapter 2 he credits the eye with ability to perceive shadow detail and highlight detail at a contrast ratio exceeding 1000 to 1.

He estimates the contrast ratio captured by motion picture film at about 250:1 or 500:1 for some of the newest film stocks and this is for the camera original. This may give a range of 8 to 9 F-stops. Subsequent film prints lose contrast range.

When I used to shoot clay animation and commercials on 16mm reversal stock (usually the old Kodak 7252 ECO, which was designed to be low contrast, or a stock called VNF in the 1980's) you could see good shadow detail on the camera stock but transfers to video at a lab like MPL would visibly lose shadow detail.

Jackman estimates pro TV cameras like the Sony DSR500 at 128:1 or 7 stops.
He estimates the Canon XL1 or Sony VX2000/PD150 at 64:1 or 6 stops.
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Old February 19th, 2006, 05:49 AM   #3
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Thanks for this Ed.

Is he saying that then human eye only does 10 stop (1000:1) at any one time? If this is the case it puts us in good stead, some sensors today can do 16 stops. I probably need to nail this more accurately.

It is confusing, with so many people say so many things around the net, but not how they are applied.

About the TV lighting, I agree, that is one of the ways our eyes tell 3D by where the light and shadow falls, so replicating it enhances the effect.
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