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Old Sep 22, 2002, 8:22 PM   #1
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Default How can you test FOOT CANDLES with a Olympus 3020

I need to know how to test for foot candles with a c3020. I know how to do it with a standard cameras. I know you need to set the film speed to 35 asa. What is that in digtal? Is there a formula like there is for film. I got rid of my "normals" for digtal. I have to over winter my passionflowers and need to know the FC of the area they will be in. I do not want to buy a meter, if I don"t have to. Anyone...
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Old Sep 22, 2002, 8:30 PM   #2
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asa and iso are now one. generally the minimum iso is 100 on a digicam.

i believe that there are charts in photo books in the library that can help you do the conversion.

[Edited on 9-23-2002 by sjms]
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Old Sep 22, 2002, 8:42 PM   #3
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Default Foot Candles

I found this on the web. I hope it is useful. Source: http://www.cybercollege.com/tvp017.htm

Minimum Light Levels for Cameras

Television cameras require a certain level of light (target exposure) to produce good-quality video. This light level is measured in foot-candles or lux.

A foot-candle, which is a measure of light intensity from a candle at a distance of one foot (under very specific conditions), is the unit of light intensity often used in the United States (although the term is now being replaced by lux.) The origination of the term "lux" is not known, although it's assumed to refer to lumens (a measure of light power) times ten.

Since we'll refer to both lux and foot-candles throughout these modules, you'll need to know that a foot-candle is equal to about 10 lux. (Actually it's closer to 10.76, but 10 is generally close enough, and it's much easier to use in conversions.)

Although they will produce acceptable pictures under much lower light levels, most professional video cameras require a light level of at least 75 foot-candles (750 lux) to produce the best quality video.

With consumer-type camcorders you will find advertising literature boasting that a particular camera is capable of shooting pictures under less than one lux of light. But, the question arises, "What kind of picture?"

The light falling on a subject from a 60-watt light bulb 3 meters (10 feet) away is about 10 lux. If you have ever taped anyone under this light level with a consumer-type camera, you know that you can't expect impressive video quality.

Although the EIA standard is in place in the United States to specify minimum quality standards for light levels, adherence to this standard is not mandatory. Since manufacturers know that consumers want cameras that shoot under low light levels, they are reluctant to use the EIA standard and look inferior to a competitor who is not adhering to the standard.

Suffice it to say, if you are in the market for a camera and you don't see the EIA standard specified, you need to check out any low-light level claims. By just zooming in on the darkest corner of the room and observing details in the black areas, you can make a rough comparison of the light sensitivity of different cameras.

At low light levels the iris of a camera must be wide open (at the lowest f-stop number) to allow in the maximum amount of light. As the light level increases in a scene, the iris of the lens must be stopped down (changed to a higher f-stop number) to maintain the same level of exposure on the camera target.

Under low light conditions video can quickly start to look dark, with a complete loss of detail in the shadow areas. To help compensate, professional cameras have built-in, multi-position, video gain switches that can amplify the video signal in steps from 3 up to about 28 units (generally the units are decibels or dB's).

But, the greater the video gain boost, the greater the loss in picture quality. Specifically, video noise increases and color clarity diminishes.
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