[list][*]Open pic and duplicate the layer[*]Select the blending mode color dodge for this layer[*]Invert this layer (ctrl + I) (don't be scared if the layer turns suddenly white)[*]Add a Gaussian Blur between 0 to 15 (try to experiment and don't make the lines too thick)[*]Merge the visible layer by pressing ctrl + E (merge visible)[*]Now image/adjust/threshold to kill the color and add depth to the lines.
Play with the little triangle below the histogram for the tweak[/list:u]

Have fun and show us some of your results

Rick

Good technique there Gauss

Here is my first go

jpfitness

Here is mine...............
sfm

jpfitness

he he he fun fun fun........
sfm

Blinky2004

Hey a great technique for this effect, nice find G.

Try this also for just a little more control:

After merging down, Desaturate the layer and add a LEVELS Adjustment layer. Tweak the black point slider to achieve the same results as Threshold, but with more control over the midtones -- by adjusting the Midtones slider.
And then to add more of a Halftone or Mezzo look to it, set the Blend Mode of the Adjustment layer to Dissolve, and drop the Opacity to about 50% or so -- play with that to suit taste.

[excited]

Blinky2004

Example...

jpfitness

like this?
sfm

Nice work guys [righton]

After some experimenting, I noticed that you get the best results if you start with a large document and resize it down; just try it.

Important; don't force yourself to bring out ALL the details when you apply the gaussian blur (less is better), because the final details will come out when you apply the threshold.
If you apply too much gaussian blur, you will get thick lines and not the typical thin pencil lines.

jpfitness

I will have another go - I applied a 9 g-blur first time and then 15 the second time around (on the second image)
sfm

wbiss

Nice quick & easy method Gaus! Thanks for sharing same...[righton]