Adrian On 2/12/02 at , Adrian Turner <mail@> wrote:
> > > O.K,it's Monday morning and I've got a really simple question.. > > If I am to produce archival inkjet prints (black and white and colour) ,am I > going to suffer from metamerism? Can this be avoided? expanded technical note on metamerism [Albert Edgar of ASF]. Cyan dye absorbes red light, not green, and not infrared. Where does red become infrared? The human eye falls off gradually as red deepens into infrared. If the cyan dye opens too soon in the near infrared, then the eye sees that infrared as red. This makes the cyan dye appear weak under light that is rich in infrared, such as an incandescent light, and a print made with that cyan will have reddish grays under infrared rich light. If you boost the amount of cyan to neutralize gray under incandescent light, then under light that has no infrared, such as flourescent, the cyan will be too strong and grays appear cyanish green. Too bad they don't offer a cyan dye that overabsorbs infrared, because it would have a reverse metamerism, making grays cooler under warm incandescent light, and warmer under cool lights like flourescent and daylight. Physics does not preclude such cyans, they exist, but dyes that absorb infrared are more rare. Also watch out for the <feature> often incorrectly termed <metamerism> (<metamerism> is a term which, when used correctly, describes a different, but arguably related, occurrence in colour matching. The best example I've read of this [thanks Rudy Vonk] is of the woman who buys matching shoes and handbag under shop florescent lights and finds they are not a match at all under daylight.), that's a <metameric pair>, sometimes alike sometimes not . me: In printing (especially on inkjets) the term <metamerism> is often misused to describe a feature of some inks and / or papers, which shows up as tonally localised shifts in gray balance, when prints are viewed under differing illuminants. We're now calling this <illuminant metamerism>, since it's the lightsource that changes the single object [the print] - the reference, neutral image is imaginary [so we don't have a <metameric pair>, we never did]. want to know motre? go to: http://www.neilbarstow.co.uk/links.html there is a link to an article by the great Brian Lawler on metamerism. Regards NeilB - - - - Consulting in Imaging & Colour Management - - - - custom scanner and printer profiles, training on Trident & Imacon Scanning - - - - - we supply Gretag and eyeOne, also XRite & OptiCal - - - - - - p:44 (0)1273 774704 m:44 (0)7778 160201 http://www.neilbarstow.co.uk/ http://www.apple.com/uk/creative/neilbarstow/ =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
