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Re: [OM] exposure for star photos

Subject: Re: [OM] exposure for star photos
From: "george" <geanders@xxxxxxxxx>
Date: Thu, 2 Sep 1999 17:26:42 -0700
Chris;


Right, I see we were talking about 2 diff things.

Your star shots were at F/8?  On what film?

George




>"George M. Anderson" <george@xxxxxxxxxxxxxxxxxx> moved upon the face of the
'Net and spake thusly:
>
>> > Stars are a point source---f/stop is irrelevant
>>
>> Have to disagree. F/stop very relelvant due to lens imperfections at
>> wide open apertures.
>
>Allow me to rephrase.
>
>"When calculating exposure, the usual relationship of f/stop to
>exposure does not apply.  For normal images, a 300mm lens at, say, f/4
>and a 28mm lens also at f/4 give the same exposure.  For point sources
>this is not the case---exposure is proportional to diameter of
>aperture, rather than ratio of focal-length-to-aperture-diameter."
>
>Concern for minimal aberration is why I shot my starfield slides at
>f/8 rather than wide-open f/2.5.
>
>cjb



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