Make a Photo a Sketch

Open your photo in Photoshop and desaturate it (Image — Adjustments — Desaturate).

Duplicate the background layer by dragging it to the Add Layer icon, and invert the new copy (Image — Adjustments — Invert).

Set the inverted layer to Color Dodge blending mode, and your image should be totally white.

Go to Filter — Blur — Gaussian Blur, and apply a Gaussian Blur. Ignore the small preview window — look at the image itself. Adjust the blur until you get the pencil sketch you want.

I’ve notice that this doesn’t always work with every photo so well, but often you can play with the original, shifting the levels, burning an area to make it darker, dodging others to make them lighter before doing the above trick.