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bobrobert wrote:You seem to be making a mountain out of a molehill...if that is what you want and the camera will select the shutter speed
BrigitDoon wrote:Zoom in and watch what happens to the shutter speed. It will compensate. The inverse square law does apply. Twice the distance away means a quarter of the light is reaching your lens.
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a "point source" (subject to 1% error) is obtained from a "psuedo[sic]-point-source"...at a distance 10 times the source radius (5 times the diameter). A four-foot fluorescent lamp is (almost) a point source (subject to 1% error) at a distance of 20 feet. Similarly, as one gets closer to a fluorescent lamp the apparent brightness will increase up to a certain distance (because the viewing angle (sampled area) remains constant and closeup (1 foot away) the entire fluorescent tube can not be viewed), after which the intensity will not continue to increase (as it would with a (pseudo) point source).
hungryjoe wrote:...there are simpler ways to calculate exposure, either with a meter (flash meter for flash), using guide numbers (a separate problem) or using (usually) on camera flash which automatically calculates how much light should be generated.
scottwramsay wrote:Joe, you're re-phrasing with what I just posted.hungryjoe wrote:...there are simpler ways to calculate exposure, either with a meter (flash meter for flash), using guide numbers (a separate problem) or using (usually) on camera flash which automatically calculates how much light should be generated.
I agree with you there too - my point wasn't that I want to be able to calculate exposure with the inverse square law, just that no-one else seemed to understand that moving away should reduce the light reaching you.
hungryjoe wrote:You are not measuring the light reaching you...The only two ways I know (apart from the guide No. scenario) of determining the correct exposure are ... or (b) measuring the amount of light being reflected from your subject.
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