Originally, apochromatic lens were intended for process work. Separate negatives were exposed for the cyan, magenta, yellow, and black separations. The all needed exactly the same reproduction ratio so could not be refocused for the various separations.
For general photography there were (are) very few lenses that meet the optical definition for apocromatism. The various manufacturers use their own definition for how far off the focus for each color can be, and very few of them publish that definition. Most, if not all, depend upon depth of focus to make up the difference. --graywolf ------------------------------------------------- The optimist's cup is half full, The pessimist's is half empty, The wise man enjoys his drink. ----- Original Message ----- From: mike wilson <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, November 22, 2001 3:49 AM Subject: Re: Layers, Sharp Focus, and New-Fangled Color Film > Hi, > > Shel Belinkoff wrote: > > > > Recent threads have got me to thinkin' about this new-fangled colour > > film. B&W film generally has but one layer, and color film has three or > > four layers. Now, when one focuses, does all the light converge on one > > plane? > > This is something which has intrigued me since the introduction > of "apo" lenses. Assumedly, film manufacturers are striving to > create better colour, etc, and thereby causing the film to > become marginally thicker. Contrariwise, lens manufacturers are > convincing us that we should be buying lenses which focus light > of all colours in the same plane. > > A paradox of the first order, unless..... the margins of error > are so small as to be unnoticable. No, perish the thought that > this could all be marketing speak! - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
