Weekly Assignment #132: Measuring Candlepower
Nikolai
Registered Users Posts: 19,035 Major grins
Kids are back to school, so why don't we follow them, at least temporarily. time for some fun physics experiment, involving, of course, photography:-)
Let's find out how much candlepower some of the familiar light sources carry.
The idea is simple: first take a picture of a candle, close and personal. expose to the right, but not overexpose. You would probably have to use some high ISO value or longer exposure times, but that's OK. At this point we don't even care if the picture is sharp of totally OOF. All we need is the luminance read.
Next get a an exposed (no shade) light bulb (clear, not white/matte) - no need for super bright, 40W is OK - turn it on and expose for the filament, trying to get the same reading histogram wise as you did with the candle.
Now you have both reading and can tell for yourself how many candles does your light bulb replace.
NOTE: to be more accurate, you should use identical diffuser in both cases rather than bare flame/filament.
Your entry should include both images with the pertinent exif data, preferably the screen shots of the histograms and your final calculations and results.
Let's measure some candlepower!
Let's find out how much candlepower some of the familiar light sources carry.
The idea is simple: first take a picture of a candle, close and personal. expose to the right, but not overexpose. You would probably have to use some high ISO value or longer exposure times, but that's OK. At this point we don't even care if the picture is sharp of totally OOF. All we need is the luminance read.
Next get a an exposed (no shade) light bulb (clear, not white/matte) - no need for super bright, 40W is OK - turn it on and expose for the filament, trying to get the same reading histogram wise as you did with the candle.
Now you have both reading and can tell for yourself how many candles does your light bulb replace.
NOTE: to be more accurate, you should use identical diffuser in both cases rather than bare flame/filament.
Your entry should include both images with the pertinent exif data, preferably the screen shots of the histograms and your final calculations and results.
Let's measure some candlepower!
"May the f/stop be with you!"
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