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Paper Chase - On frog juice and other magic potions - part 2 of 1 2 3 4

by Mike McNamee Published 01/04/2004

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The Highlights



The effect of the varnish is to depress the highlight tone from 95.79% to 93.64% i.e. on the order of 2%.This is detectable and if the spectral response is measured then the uv peak at 400nm has been chopped off. This has the visual effect of removing some blue from the white tone which makes it look more yellow if the coated and uncoated materials are compared side by side. It is actually made more neutral, it moves from Lab coordinates of 1 -3 (i.e. blue) to 0, - 1 (i.e. less blue).

The Mid Tones



The mid tones are depressed by 4.5% for the matt varnish, 6.5% for Satin and 7.1% for the gloss.There is no visually discernable change to the colour of the greyscale and spectro results indicate a shift from green bias to redmagenta moving from ¾ tones to ¼ tones.The varnish does not change this shift.The bespoke profile made for the testing produced a near perfect neutral as a starting point.

The Shadows

The Dmax values are shown in the table. This is the nub of the improvement - the linearity is straightened and the roll off in the toe is eliminated. The brightness value is dropped ffom around 17.8% (which is quite good) to 8.5% (which competes with gloss and lustre papers. Thus the improvement from the use of the varnishes is considerable. The difference between the matt and either the Satin or gloss results are readily discernable by eye, the densitometer reading confirm the results. The value of 2.08 from the gloss varnish is up with the best achieved on photographic silver halide prints.

The Tone Contrast Curve

In order to put some order to our measurements, a strip of three graduated grey scales was made onto the same piece of paper. This was measured before varnishing and then each strip was given two coats of either Matt, Satin or Gloss varnish, checked for coverage in uv light, allowed to dry and then remeasured. The results were plotted as shown.

They indicate that there was a slight lightening in the blacks due to the matt varnish but significant deepening of the shadows with both Satin and Gloss varnishes. This is reflected in higher Dmax values and the smaller Lab brightness reading. The highlights moved very slightly lower in density for all varnishes. With the satin and gloss varnishes the mid tones were depressed and the shadows depressed yet further. This is effectively an increase in contrast depending on how you do the sums it is of the order of 7% to 10 % change. The curve shape in the shadows is most affected as the toe is straightened.

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1st Published 01/04/2004
last update 09/12/2022 14:56:17

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