Reply to thread

Message

<blockquote data-quote="WayneF" data-source="post: 415371" data-attributes="member: 12496">Print shops did use 18% cards for many years before photography, to judge their ink levels on a 50% screen pattern.&nbsp; It is a human eye response thing.But actually, for photography, 18% was all Ansel Adams idea, with his Zone System in the 1930s (printing analog film on analog paper). The first light meters started about then too, and&nbsp; Kodak always advised if metering on their 18% gray card, to open aperture half a stop more.&nbsp; Which is 12%, which is how modern light meters calibrate (Sekonic, Nikon, Canon, all 12.5%. Others like Minolta used 14%, about 1/6 stop different).&nbsp; Kodak and Adams had many discussions, and due to his influence, it seems Kodak did not choose to make an issue of the number.&nbsp; &nbsp; Kodak sold some media business parts (including the gray card) twenty years ago, in 1995, and this half stop advice was generally lost then. The Kodak cards thereafter were NOT from Kodak.Gray cards are sort of an analog film thing, 18% is near middle gray.&nbsp; Digital is different, 18% is 18%.What is interesting is that so many think photographing a gray card ought to appear at histogram midpoint.&nbsp; But the word Middle has many uses... <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" />&nbsp; &nbsp; 18% is 18%, and in digital form, it ought to appear at 18%. However, our histograms are always gamma encoded, which makes 18% shift to about 46%.&nbsp; Which is near middle, and not a large error, but an error.&nbsp; But a really HUGE error in concept, 18% has nothing to do with histogram 50%.Conceptually, it might be best to think in terms of middle gray.</blockquote>

[QUOTE="WayneF, post: 415371, member: 12496"] Print shops did use 18% cards for many years before photography, to judge their ink levels on a 50% screen pattern. It is a human eye response thing. But actually, for photography, 18% was all Ansel Adams idea, with his Zone System in the 1930s (printing analog film on analog paper). The first light meters started about then too, and Kodak always advised if metering on their 18% gray card, to open aperture half a stop more. Which is 12%, which is how modern light meters calibrate (Sekonic, Nikon, Canon, all 12.5%. Others like Minolta used 14%, about 1/6 stop different). Kodak and Adams had many discussions, and due to his influence, it seems Kodak did not choose to make an issue of the number. Kodak sold some media business parts (including the gray card) twenty years ago, in 1995, and this half stop advice was generally lost then. The Kodak cards thereafter were NOT from Kodak. Gray cards are sort of an analog film thing, 18% is near middle gray. Digital is different, 18% is 18%. What is interesting is that so many think photographing a gray card ought to appear at histogram midpoint. But the word Middle has many uses... :) 18% is 18%, and in digital form, it ought to appear at 18%. However, our histograms are always gamma encoded, which makes 18% shift to about 46%. Which is near middle, and not a large error, but an error. But a really HUGE error in concept, 18% has nothing to do with histogram 50%. Conceptually, it might be best to think in terms of middle gray. [/QUOTE]

Verification