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Old 07-25-2016, 10:56 AM
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tyro tyro is offline
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Join Date: Aug 2006
Location: Scotland, U.K.
Posts: 3,538
Default How to piss off your astrnerd friends.........!

Ciao cara Lisa,

Thanks for all that interesting techy stuff. I love it. Just imagine how a Sony can be better than a Canon at this game and that a really cheap superwide lens can be the canine ovoid things for astrophotography! Just a pity Samyang didn't do long lenses for wildlife - actually I think they do make 500mm and 600mm reflector lenses but I don't think they're in the same league as their wide angle primes.

Anyway, if your astrophotography nerdy friends are getting a bit too big for their boots, ask them about the Schwartzschild Effect - otherwise known as "Reciprocity failure". I remember reading about this years ago when I tried to take long exposures at night with film. Essentially, if you take a shot at, say, 1/100 sec at f/8 that is the same exposure as 1/50 sec at f/11 or 1/200 sec at f/5.6 because the same amount of light is allowed through to the film or sensor. But, when you get into the realms of very long exposures in very low light, films require more light for extremely long exposures - so an exposure of, say, 5 minutes at f/5.6 might need a lot more than the expected 10 minutes at f/8.

Actually, the Schwartzschild Effect only really affects film as digital sensors have a much more linear sensitivity to light - but you might just be able to piss off your friends with this nerdy talk - just try dropping it in as a quick aside while having a beer with them around the camp fire.

Un abbraccio,

Giovanni.
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