In message Tue, 10 Feb 2004, Tony Riley writes snip
Dear Tony
Thanks for this contribution and your earlier one...Yes the pdf was very interesting but the problem is I am looking for big file sizes for this application and this means scan back.
We believe that side-by-side comparisons of actual fade (density decrease) and color shifting (deltaE differences) is the best way to determine how well an ink performs.'
Sounds right to me, but it's useful to have a numerical number too. Snip
Your question is interesting - by 'fading' do you mean 'colour difference'?
Indeed.
A print can 'fade' quite a lot before the human visual system can detect it. A colour difference of less than 2 delta E is considered imperceptible,
I believe that deltaE 1 is the smallest difference that most people can detect, however if it's a colour change in a neutral it comes right down to .5!
2-5 acceptable in one respected study (Stokes, Fairchild and Berns 1992). There are different percepual responses to pictorial images and pigment patches, and other methods of measurement (e.g. delta E94, based on D65 brather than D50). Perception of any colour is massively influenced by surrounding colour, both in subjects and images.
That's why we should carry out all our colour evaluation and editing in a boring old grey enviroment...quite restful actually.
There are other aspects not generally considered in the fading debate, such as paper yellowing, mentioned among others by Epson (http://www.dpandi.com/resources/permanence/cpd-15334_1102.pdf).
Good point often forgotten.
I sell fine art prints through an art gallery, so am pretty concerned about what I say to customers about longevity.
Do your customers ask...not that I am suggesting you shouldn't inform them<G>
snip
In the end we may be left with the ridiculous situation that a longer lasting combination with more honest and stringent conditions could actually achieve a 'lower' rating than a shorter lasting combination with less stringent test conditions.
Honesty sometimes does not sit happily with marketing , but then what's new.
My brother runs a major UK ink manufacturers, and I know he sticks prints on the window to see if they fade as well as having Wilhelm tests done!
That's the way I do it. Have a known control and base the results against that....a real world test but totally unscientific, but then customers don't display prints in some test lab do they and the customer is king/queen<G>
Cheers
Richard -- There are scans and there's Drum Scanning, get the advantage, get the pdf! =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
