I can't imagine that any of my artist customers would be able to come back every four hours to view each hard proof whereas a 5 minute wait for the HP proofs would be no problem for them.
So how can Epson HDR inks be a realistic proposition for proofing when the client wishes to be involved while he/she waits?
Ryan Grayley
Short term color drift is a very significant issue with dye-based inkjet printers. The color can take days or even weeks to settle which is why dye based inkjet printers have fallen out of favor for graphic arts proofing applications. By comparison, all of the latest aqueous pigment sets from Canon, HP, and Epson, settle to a final color state quite quickly and, IMHO, short term drift is comparable for the Hp Vivera, Epson K3/K3VM/HDR, and Canon Lucia/LuciaEX ink sets. AFAIK, there is no standardized ISO or ASTM short term color drift test, so the manufacturers are pretty much free to measure the phenomenon as they see fit, and thus their different approaches may translate to market speak that makes the performance among these ink sets sound more different than it really is.
As digital dog noted, for building profiles you would conservatively want to give a printed target the benefit of a few hours drying time (and, ideally average your readings over more than one target sample), but otherwise, typical print-to-print variability and even spectrophotometer measurement repeatability are likely to introduce as much error in the measurement of individual print color values as the short term drift component in these pigmented ink systems. Moreover, Delta E equations were designed for side-by-side solid-fill color patch viewing conditions where the color difference between two swatches is being judged solely for color's sake. Real images typically present a far more complex array of color and tone patterns to the viewer and under these conditions people judge individual colors in context with the surrounding colors and tones. The oft-quoted visual discrimination threshold of delta E =1 relaxes greatly in the delta a*b* component for increasingly higher chroma colors in complex scenes while delta L* = 1 deviations between neighboring tonal values may still wreak havoc with subtle but important tonal contrast gradients in an image. Hence, image color and tone reproduction accuracy truly deserves an entirely different evaluation method than simple delta E metrics (pick any flavor, delta E, delta E CMC, delta E2000, etc) which otherwise work quite well, for example, when trying to match two batches of paint or solid-color fabric samples .
I would qualify these remarks further by also saying that the short term dry-down issue is of more concern to proofs and actual press runs involving spot colors like matching a corporate color, say Coca Cola Red or John Deere Green. In this application, delta E equations are reasonably valid because the spot colors are being judged once again in side-by-side isolation rather than as specific information content residing in a photorealistic image. The corporate client may contractually demand precise colorimetric matching of a particular spot color, and the final color may actually be getting handled on press with a custom blended spot color ink rather than trying to reproduce with CMYK process color. But for the vast majority of artists seeking a high quality fine art reproduction or photographers seeking a pleasing translation of digital image file to hard copy print? Any short term dry-down color drift errors on these pigmented ink printers are overwhelmed in comparison by the total overall color and tonal remapping which inevitably must occur and which invokes huge delta E variations between original image colors/tones and final print colors/tones.
regards,
Mark
http://www.aardenburg-imaging.com
