I just got back from my old office. All the prints are still hanging and the colors look very good. The papers were Hahnemuhly Photo Rag Ultra Smooth, Ilford Gold Fibre Silk, and Museo Silver Rag. 10 images are hanging, all framed behind normal Acrylite and two are monochrome. The average LUX reading was 332 with a high value of 401 and a low value 258. The lights are on for about 13 hours a day. All the images are in the hallway and none receive any sunlight. As noted the pictures have been hanging since late 2008 and were printed on an Epson 3880.
Alan
Alan, your measured range of 258 to 401 lux is pretty consistent with typically quoted values for good office lighting conditions, although I was expecting a little more variablity from low to high.
If we take the measured high value for daily exposure as 400 lux for 13 hours per day we can make a "worst case" estimate with respect to the total accumulated exposure to date.
400 lux x 13 hours/day x 365 days/year x 9 years x (1megalux/1000000 lux) =
17.082 Megalux hoursAssuming you printed with an Epson printer and K3 ink set, I found some Aardenburg test results for the papers you used. The worst two Aardenburg Conservation Display ratings among those I found were 51-84 and 59-95 megalux hours, respectively. If we then take the 51 megalux hour lower CDR limit as the worst case situation where just noticeable fading begins to occur, then your prints are still well within their “period of excellence” where essentially no fading is going to be observed. In fact, these prints on display in this location have at least 18 more years to remain in excellent condition at this estimated light exposure rate!
Consider if you had made conventional wet process chromogenic color prints instead of these K3 pigment prints and place under same display conditions. Aardenburg predicts a Conservation display rating for Fuji Crystal Archive at approximately 12-28 megalux hours. Your “period of excellence” would almost be used up entirely. Those prints would still look good today, but in another nine years they would then be into the “noticeable fade” stage of their print life, and 18 years from now would be well into their “easily noticeable fade” stage of deterioration, whereas the K3 pigment prints on your chosen papers, albeit then having consumed their full Conservation rated display time, will thus still look essentially fade-free.
Or consider if you had used a high OBA content paper like Epson Ultra Premium Presentation paper (aka, Epson Archival Matte). It scored an 8-103 meglux hour Conservation display rating with the K3 ink set, the upper CDR limit being extended because the strong media white yellowing is off-setting some of the K3 yellow fading in various colors on average. Thus, while many areas in an image would still contain colors and tones in excellent condition, the media white print margins and white areas as well as many highlight colors, especially light blue colors, would now be exhibiting noticeable color changes. The OBA fading is largely responsible for the visual outcome in this example.
Lastly, consider what might have occurred if you had elected to use a third party “K3 equivalent” ink set to make your prints. I have one popular brand in test at the moment (data not yet posted to the Aardenburg database) that more than likely is actually a dye-pigment hybrid ink set. Some third party inks do significantly better in Aardenburg testing than this one, but this one is going to get a rating of approximately 2-5 megalux hours despite being sold as a high quality replacement ink set for printer models using Epson k3, K3VM, or even HD inks. Without published fade test results, who would know? In some commonly encountered home display conditions under 100 lux/12 hour daily illumination, this product would still be relatively fade-free at your nine year mark on display and the buyer would likely feel justified at his/her purchase under those circumstances, but in the office condition you have measured, easily noticeable fade would have already occurred at your nine year mark. I wouldn’t want my signature on those prints!
I hope Alan's real world lux level measurements in a specific display location along with the extra examples of print process choice I discussed above help to inform folks why choosing print processes wisely is one important part of the print longevity puzzle. The other is display lighting. Real world variability in display illumination levels accounts for very large differences in print fading outcomes even when considering just one print process (e.g., printer/ink/media). It is why for the materials and processes we test, Aardenburg posts megalux hour ratings, and we hope you own a light meter
.. in order to make a more informed decision with respect to "how long will my prints last?".
cheers,
Mark
http://www.aardenburg-imaging.com