Hi Luciano,
I looked at your scan of the step wedges and I think you are just seeing natural variations.
First the there's the dithering while printing the wedge and then there's the randomness of
the scan. If you just take the ink sampler in Photoshop you can be sampling one pixel at
a time or a small block. Just moving around in a single patch you can see quite a variation
probably mostly because of the dithering dots -- dust specks on the scan can also do it.
To get a better value than using the eyedropper what you can do is draw a small square
inside a patch -- avoid the edges and where the number is. Then in the Histogram pane
you'll see a Mean i.e. average of all those pixels. The value is 0 (black) to 255 (white) so
you'll need to convert: K = 100 - (x/2.55) to get percents.
Another thing to remember is that the file values are always 0 to 255 so K=50 is a calculated
value. The internal could be 127 or 128 or better half each. If you can steep curves this can
make a difference.
Roy
On Sun, Apr 6, 2014 at 2:18 AM, <luciano@...> wrote:
I do select my own profile, but the point is that the same step should always print with the same density. Or am I missing something?
In any case, I tried also using System Managed for Print Color Management, and QuadToneRIP in Color Matching. The problem remains. Any other ideas? Thanks.
Luciano
Roy Harrington
roy@...
www.harrington.com