Almost any object, whether it's a photograph, an illustration or even a vector drawing can be modified in Photoshop to appear as a very detailed sketch.

To start, you need two duplicate transparent identical layers with the object you want to apply the sketch effect to in them. Here are the steps:

1. On one of the transparent layers, use the "find edges" tool which is located on the "Filter" menu under "Stylize."

2. Next, desaturate the layer. Desaturate is on the "Image" menu under "Adjustments." It is also possible to access saturation values under "Hue/Saturation" in the same menu.

3. Next, open the "Levels" dialog box which is also on the "Image" menu under "Adjustments." Adjust the levels until the image looks a little like a sketch. The sliders under the graph can be used to make adjustments.

The more you make changes to the levels values, the more the style of the sketch will change.