Re: filmscanners: Q60 scanner gray scale tests

[Mike Duncan <mgduncan@esper.com>]

Cliff wrote:

>You can get Stouffer step tablets from www.darkroom-innovations.com. I just
>got the 35mm step tablet with 21 steps, .15 density/step (uncalibrated), for
>$25.95 with ground shipping (only took a couple of days). This will give
>your scanner a good workout. My SS4000 bottoms-out around the 19th step.
>
>The Stouffer tablets are photographic silver, so they are pretty neutral.
>The Q60 gray scales are not truly gray - just look at the L*A*B* values in
>the data file to see how much your Q60 deviates.
>
>You can get Kodak brand step tablets from www.tiffen.com. Look in their
>Kodak Professional Accessories catalog. They have calibrated, but they're a
>lot more money.
>

Thanks Cliff.

I bought the Stouffer step tablet.  Looking at the 35mm tablet, it's
difficult to distinguish anything denser than step 19, so your SS4000 did
as good as my eyes.  Using Apple's DigitalColor Meter (which agrees with
Photoshop), my Minolta Diamage Dual (SCSI) with Vuescan with black and
white clip at 0.001 and brightness at 1, it bottomed out at step 17.  RGB
tracking was good from step 1 to 11, but began to diverge at step 12 and
above.  Linearity was good up to step  14 and the slope began decreasing
above that. From 17 to 19, the slope is nearly 0, and above 19 the slope is
0.   On the monitor, it was difficult to discern any difference beyond step
15.

>From this test, one can assume that Adobe's RGB and Brightness numbers (PS
4) are proportional to intensity, using the default color space on a Mac.

Mike Duncan