On 02/12/02 14:40, michael shaffer: > Are fluorescing agents in some of the papers recognized as contributors?
Illuminant metamerism is a combination of three things: Illumination, substrate and our eyes. If any of these things change our perception of things change. This happens all the time when we walk from daylight to a room with tungsten light, but as our eyes have the ability to compensate (white balance) in different lights this is rarely something we notice. What we do notice though is when colours change direction in unexpected directions (such as neutral colours appearing green in daylight). The reason why this is happening is that certain substrates (ink and paper) reflect different parts of light depending on the wavelength of light that shines upon it. Fluorescent agents in either ink or paper can certainly contribute to metamerism: Fluorescent materials fluoresce because the materials absorb colours of a wavelength shorter than visible light (UV) and reemit this light in the visible spectrum. So if we suppose some genius poured fluorescent agent into the Yellow or Magenta ink, to make it more vivid (think road workers yellow/orange clothing) this would certainly create illuminant metamerism. Remember these colours only fluoresce when UV light hit the fluorescent agent, and there is considerably different amounts of UV light if you compare an overcast day, daylight (the sun) and a halogen bulb, so the colours of the entire image would change depending on the light source... It is less pronounced when we talk about optical brighteners in paper, as most of these agents simply make the paper appear "whiter", but again this effect will change depending on the light source, and as such it does indeed contribute although the effect may be negligable... Best Regards Thomas Holm / Pixl ApS - Photographer & Colour Management specialist - Adobe Certified Training Provider in Photoshop� - Imacon Authorized Scanner Training Facility - Remote Profiling Service (Output ICC profiles) - Seminars speaker and tutor on CM and Digital Imaging etc. - Home Page: www.pixl.dk � E-mail: [EMAIL PROTECTED] -- =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
