A pretty cool effect....
In Photoshop open an image, and duplicate this first layer. With the new layer selected, go to image-adjustments-desaturate. Duplicate this layer, and change the blending mode for this new layer to color dodge. On this third layer, go to image-adjustments-invert. The canvas may turn completely white, that's ok. Finally, go to filter-blur-gaussian blur and adjust the slider to your taste, a cool sketch effect.
