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Fade & Line Quality Testing - part 3 of 1 2 3 4

by Mike McNamee Published 01/02/2006

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On the light fastness front, lives of between 100 and 200 years are being projected for K3 inks especially when combined with spray-coated varnishes. PremierArt Spray has been the most tested at Wilhelm Research, but the DCP Giclee varnish has always offered a massive toughening of a surface, as well as both ozone and moisture protection. With DCP varnish, the most savage test we have heard of is from member, Andrew Williams, who spilled paint onto a varnished canvas and still got away with it via a turpentine-loaded rag - not recommended, but a spectacular test! DCP has also improved on one of the niggles with aqueous-based, paintedon varnishes, by the addition of an anti-foaming agent. Varnishes applied to stretched canvas both before and after are assisting in toughening up the surface to provide both abrasion resistance and edge-cracking resistance.

Metamerism has always been the bane of the printer's life. For those who are unfamiliar with the term it describes the apparent colour shift when you move a print from one type of illumination to the other. It has always been more of a problem with pigment inks compared to dyes but as you read earlier, we don't do dyes! Various solutions have been proposed, from specialist ink sets such as Permajet MonoChrome Pro and VT Blax, through to specialist RIPs which slice out the badly-behaving yellows. Epson has made massive strides in that the K3 ink set has reduced the metameric index by quite a way, whilst giving the photographer superb colour as well - this is vital for combined mono-colour effects on a portrait or album page. The introduction of the original Epson Gray Balancer in a user-friendly guise as Advanced Black and White is also most welcome. Making fine-tuned toning biases to your mono is now a piece of cake.


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Ink-jet printing speeds have been improved such that we usually print at 2880dpi these days and to heck with the additional time! This is however, not for everybody and for balance we should point out that the specialist laboratories are now offering very competitive prices for high-quality digital printing to traditional media. They also have the edge when it comes to the gorgeous metallic finishes, which add such a lift to your album pages.

Looking to the future it seems unlikely that the paper chase will be called off just yet, the hounds are still hungry and there are no foxes to chase any more! With both Focus and Photokina to come, who knows what the future has in store - happy hunting!

All about the Lab

At the prompting of David Anthony Williams during a discussion at the Convention, we repeat and expand on how to interpret an error plot set out in Lab. Lab mode splits the components of a colour into three parameters, two of which deal with colour and the third which defines the lightness or darkness. They are the lightness value L, the a value which specifies the redness to greenness of the colour and b which defines the yellowness to blueness of the colour. Thus you divorce the lightness-darkness from colour and if you have an image of a person's face lit from the side, the Lab a and b values will be the same on both cheeks (give or take a point) but the lightness value will change quite lot.

Using Lab makes assessment of colour easier as you can look at the colour elements (the colour - is it green or blue and the saturation - is it pure and vibrant or dull and neutral?). Small values of a and b represent colours close to the neutral point (a=0 b=0) large values of a and b represent strong vibrant colours. The actual mix of a and b determine the hue to define the colour as green, cyan, blue, etc.


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1st Published 01/02/2006
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