Isolate gray values?

[HammerB]

Hi, If i have a node with different values of gray (like the random color in a tile sampler) and i want to isolate separate each value (or range of values) separatedly, how would I should procede?
 I'm trying all the "histogram select/range/scan" nodes thinking that those could be the answer but I can only isolate the darker ones, what I want is something that i could select a gray level or a gray range and mack everything else (above and below that level) black. Am i using the histogram nodes wrong, there is something else I should do or it's just I'm not using the right node?

[disOrder66]

The 'Color to Mask' node can isolate a single value or a range of values.

The attached image shows isolated values blended with a black background.

Double-click your source node to view it in the 2D View.
Single-click the 'Color to Mask' node.
In the Instance Parameters, select the Eyedropper and sample a value from the 2D View.
Double-click the Blend node to view it in the 2D View.
Single-click the 'Color to Mask' node and adjust the Mask Range.
For the Keying Type, use Luminance or RGB.

[horst-peter]

If I understand you right, this should work out to isolate the parts you want. It's the basic principle of a node I use for my greyscale material mask workflow. Hope it helps.

[divi.cig]

histogram select is the node you want for creating a mask. very high contrast, low range, position is the grey value's intensity you want to get. afterwards multiply with the original if you need the mask to have the original value as the above posts have shown.

[horst-peter]

Ooh Histogram Select. Just upgraded my licenses after sticking with Designer 5 for ages and I guess I can retire or simplify a few of my self-made helper nodes now.