Date: Mon, 08 Apr 2002 06:52:28 +0000 From: "Matthew Hanson" <[EMAIL PROTECTED]> Subject: RE: Digital cameras (was [LIB] New Website
>From: Raymond <[EMAIL PROTECTED]> > >>From: David Chien <[EMAIL PROTECTED]> >> >> A lens with a big minimum aperture rating (eg. f/5.6) is a slow lens >>vs. a lens with a small minimum aperture rating (eg. f/1.8), a fast lens. >OK through all this, something is losing me. When you talk about 'big >minimum aperture', I realize you're talking about a big f-number (ie. in >fact a SMALL aperture opening). When you say minimum however does that mean >the f-number can get bigger (ie. in fact its a maximum aperture opening) or >does that mean the aperture opening can get bigger (ie. in fact its a >minimum f-number)? Because in that case it doesn't seem to make sense ... >for the same situation, I thought a fast lens lets in more light than a >slow lens so you'd expect a fast lens with a small aperture opening (ie. >larger f-number) would let in the same amount of light as a slow lens with >a large aperture opening (ie. smaller f-number) ...< Heh... 29 or so posts ahead of me, so I'm sure this must have been addressed. It's been years since I knew all of this stuff, and am still getting the cobwebs out of my attic. But I don't think that what's being defined here as 'speed', 'fast lens' and 'slow lens', has anything to do with the quality of one lens that would make it 'faster' or 'slower' than another lens at the same f/stop. Or �let in the same amount of light� at different f/stops. I always thought that the relationship between f/stop, exposure speed, and speed of film, was a fixed proportionality that is independent of what kind of lens that�s being used. I�d think that�d drive people crazy calculating settings for a bunch of different lenses. I'll be interested to see if David or Neil also explain things as I understand them. That a 'fast' lens, is one that has a bigger, well ground set of glass optical components that allow the lens to open up to the smaller f/stops, creating a larger aperture, and letting in more light. At the lowest f/stop in a 'fast' lens, you'd have to increase the speed OF THE EXPOSURE. Where using any of the larger f/stops would result in smaller apertures, and necessitate a slower exposure time. And I wonder if it is from this measure of high exposure speed at the very low f/stops that these lenses are capable of, that gave birth tow the term 'fast lens'. Matt Onward... _________________________________________________________________ Join the world�s largest e-mail service with MSN Hotmail. http://www.hotmail.com ************************************************************** http://libretto.basiclink.com - Libretto mailing list http://www.silverace.com/libretto/ - Archives -------TO UNSUBSCRIBE------- Reply to any of the list messages. The reply mail should be addressed to: [EMAIL PROTECTED] - Then replace any text on the message's subject line: cmd:unsubscribe --------TO UNSUBSCRIBE DIGEST------ Do above but with this on subject line: cmd:unsubscribe digest **************************************************************
