Michael Wilkinson wrote: > Thomas , > Surly a scanner with separate RGB light sources will perform correctly
Short answer Nope. Long answer: Separate RGB light sources? Mind explaining that? If I understand you right you mean three light sources filtered to emit energy in specific spectra which, when combined, will be similar to the spd curve of D50 light? First, to the best of my knowledge there is no such thing on the market at all. The "usual suspects" for making D50 light is filtered tungsten, or pulsed Xenon. Certain light box manufacturers produce tubes that will yield 5000K, but not D50 spectra - most are not even close and therefore prone to metamerism. If you plot the spd curves of any fluorescent tube or a monitor you'll see peaks and valleys, which doesn't mean as much when viewing things, but mean the world when measuring. Also I doubt you'd find three light sources in an entry level product. The only products I know using this technology are Printers that expose paper with Lasers (Lambda and the likes), and even those have severe problems reproducing certain colours. FYI a Lambda laser is $5-7000. A scanner (non PMT) GENERALLY function by having a sensor which is 3 pixels wide which are filtered with red green and blue one pixel wide. A fluorescent light tube is lilluminating the area the scanner is passing over. The reason for using fluorescent light is one of cost and convenience: 1) It's important to have an even light across the entire surface (those of you shooting reprographic work know that setting up 3 light sources in a confided space won't easily give you even light over a surface). 2) LCD sensors are extremely sensitive to temperature fluctuations - particularly increases in temperature, which are inherent with most continuous type light sources. But even if you could produce three light sources that gave you D50, you'd still have the deficiencies from a CCD sensor, and the Observer metamerism inherent in those. Best Regards, Thomas Holm / Pixl Aps - Photographer, Educator, Colour Management Consultant & Seminar speaker - Remote Profiling Service (Output ICC profiles) - www.pixl.dk � Email: th[AT]pixl.dk -- =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
