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> Standard Candle. |
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#1
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Standard Candle.
When I was a schoolboy our science teacher told us about standard candles for physics. He even had the composition and wick specifications to make your own.
I am wondering if there is a standard do it yourself light source to check my light meter against. All the articles that I have ever read on checking light meter accuracy have told me to check it against a known good meter. How do you know it's a good meter? I am looking for something that would tell me to use a certain wattage tungsten light bulb, opal or clear, in a dark room at so many feet or inches. I figured tungsten to be a bit more standard that the various energy saver bulbs. Anyone any experience in simple, diy standard light sources. With easily available components. Cheers . |
#2
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When I bought my Elinchom flash heads in the early 1980's they came with a comprehensive instruction sheet and it suggested metering using the modelling lights, These bulbs were non standard so you had to use the correct ones supplied by Elinchrom.
So Elinchrom had standardised on these bulbs knowing their output was consistent, obviously the flash output was much higher so there was an adjustment to make, but in the absence of a flash meter it worked out perfectly. Light output drops slightly as a bulb ages so you do really need to check against a good reliable meter for reference and accuracy. Ian |
#3
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A good meter is one you trust. My suggestion would be to use a photograph grey card place it in good light and take a meter reading with two meters and compare the results.
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Mitch http://photomi7ch.blogspot.com/ If you eliminate the impossible whatever remains no matter how improbable must be the truth. |
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Is this of any interest?
https://www.ebay.co.uk/itm/VINTAGE-G...wAAOSwKtVeYTHD I see that there's some instructions included, and they may advise how to use it. I reckon you'll need dark cloth or similar, so that you aren't affected by stray light. Check using the inverse square rule. HTH
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Malcolm Stewart Milton Keynes |
#5
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Compare meters, the more you compare the better of course but even 2 out of 3 aint bad (as meatloaf or steinman would say)
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Is there a level below "in the poop" ? |
#6
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Malcomb, you may want to check your email as it is not accepting emails as it is full.
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Cheers, Barry |
#7
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If you do not have a standard 37% grey card, the inside of a normal Kellogs Cornflakes box gives the same reading! Bet you didn't know that!
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#8
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Quote:
Either way, that's a useful tip there John! Terry S |
#9
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Wait for a sunny day in mid-June and take readings at midday. This is the reference. Your meter, set at the appropriate film speed, should then indicate the same exposure time and aperture shown in or on the film packing.
Reflection exposure meters calculate exposure on the assumption that the scene you are metering reflects 18% of light incident upon it. The Invercone on Weston Meters and the little dome on others, directed towards the light source, make incident light measurements and simulate the 18% reflectance of typical scenes. Last edited by JOReynolds; 13th March 2020 at 10:25 PM. |
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