strange color range with SF tiff

[davidh]

Hello,
I have come accross the following behaviour:
I scanned a BW image with SilverFast Ai 6.6. creating a tiff color image 48-bit (Color Profile - Adobe RGB). Since it was stained, I first highlighted the stains using SilverFast Selective Color Correction and then scanned the picture. In PWP read tool the stains show RGB - 100,100,0.
When I try to mask them using PWP Color Range tool (contract, shift + click into a stain), I can never achieve a range straight away - all three bars remain contracted. Only after I first click outside a highlighted stain somewhere else into the picture, does the HSV (or HLS, RGB) bars kind of "wake up" and create ranges for that point. I have to contract them, click again, but this time into a stain and get the ranges for the stain.

If I need to contract the stain ranges to recreate them, I have to again first click outside the stain, etc...

If I do not highlight the stains in SF, there is no problem with using the mask range tool on the stains of the scanned image.

Little bit strange and uncomfortable behavior. Is it a SF tiff problem?

I use PWP 5.0.1.6 on Windows 7.

David

[ksinkel]

David,

Try dragging the color stain tool within the stain area. It is very unlikely that all the pixels of the stain are exactly the same color. That way you will capture the variations in the stain and open up the color range tool.

Kiril

[davidh]

Hi Kiril,

I see what you mean and in fact, before I posted the message, I tried clicking and dragging in all possible directions within the stains with no success. But what is really strange about it, and that is just the reason I posted it is, that until I click outside a stain nothing happens. But after that (and after contracting the unwanted range) even one click inside a stain - no need even to drag - just one single click inside is enough to create useful range of the stain. And I must not contract it. If I do, I have to click first outside again.
Real mystery.

David

[den]

David, Kiril....

An RGB color of 100,100,0 is pure yellow and perhaps presents a discontinuity result when the "Mask Tool - Color Range" tool is in the normal HSV default or the HSL color space models... Try changing its color space model to RGB.

[den]

David, Kiril.... the above posting may have been a bit pre-mature....

Further investigation indicates the Mask Tool- Color Range tool has difficulty is selecting a specific color [one with no range] regardless of HSV, HSL, or RGB color space modes...

...this is evidenced by clicking on an image color, then Contract and Apply. No mask selection is made because there is no range in any of the channels as evidenced by the white sliders being 'back to back' rather than 'point to point'. As soon as you move the white sliders in each of the 3 channels of what ever color model selected so that their points face each other, creating a very small range, than click Apply... a mask will result.

Perhaps the color range white sliders when contracted should point towards each other rather than away!

[jsachs]

The color range tool is not designed to select single colors. One way to do something like this is to contract the range to the single color you want and then drag the sliders a tiny bit to either side to make a very narrow range.

[davidh]

Den, Jonathan,
sorry for the delay in response and thanks for the interest in this matter. I think I more or less understand how the color range works. What I did not quite understand was, why the same pure color once opens a range (though it is not supposed to; and what kind of range is it then?) and once does not depending seemingly on whether or where was the previous range contracted, as described in the previous entries.
Well, it is not always important to know why something does what it does if it sticks to regular behavior, which is what it does.
Thanks again to all.

David

[tomczak]

David, you may find this past discussion useful:

http://www.dl-c.com/discus/messages/2/12564.html