Let's see how that works.... 100% 50% 25% <18%> 12% 6% 3% 1.5% .7% .3%
Nope nope 18% is not in the center, unless you say white paper can not relect mor than 72%. As you can see above 12% is the center of a 7 stop range and 6% is the center of a 9 stop range. Actually, IIRC, Adams selected 9% as zone V which would make 18% zone VI. So why was 18% reflectance chosen as our exposure reference? Well, because, as I said, it is the average relectance of the world around us and so was chose as the reference value. So why is 18% used as a reference in graphic arts, probably because it was there. <grin> Note to Doe: the reason you can use a gray card is because when the patch is corrected to neutral gray all color cast is gone. Colors might still not be accurate but it is about as close as you are going to get. Now if you need one particular color to be accurate you need to use a color reference so the filter pack can be ajusted to that color, but then all the other colors may be off more than if you had used neutral gray as your reference point. Ciao, Graywolf http://pages.prodigy.net/graywolfphoto ----- Original Message ----- From: "Herb Chong" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, January 04, 2003 10:19 PM Subject: Re: Dumb Newbie Q - What Color ARE Color Negatives? > Message text written by INTERNET:[EMAIL PROTECTED] > >This has been bantied about the internet for some time. First let's > consider > what middle gray is. Is it an abitrary shade of gray? No it is the average > scene in mid-northern latitudes in the morning or afternoon on a sunny > summer day. That happens to be about 18% gray. That is why it was selected. > Grass, trees, etc. have about that reflectance.< > > it's simpler than that. 18% gray is basically halfway between the maximum > and minimum brightness a printed card can handle in terms of number of > stops. its approximately 2 stops below the purest white normal paper > produces and 2 stops above what the blackest black normally found in > ordinary printing. > > Herb.... >
