Here is a useful photo manipulation tutorial. Basically, this tutorial shows how to apply a skin disease or acne type condition to a skin surface in a photograph. Great for special effects editing.
1. Open a photograph of your subject in Photoshop.
2. Create a new layer over the photograph. Name it “Texture”.
3. Goto Edit > Fill. Set “Contents” dropdown box to Pattern. Choose Wrinkles pattern. Click OK.
4. You should now have the overlapping layer with the following bumpy texture on the “Texture” layer.
5. Set the Blending Mode for the “Texture” layer to Overlay.
6. With the “Texture” layer active, click “Add Vector Mask” from the Layers Palette.
7. Click the Vector Mask in the “Texture” layer so that it is active.
8. Select the Gradient tool. Set the gradient so that it is White to Black. Also be sure that the gradient is set to a Radial Gradient.
9. With the Vector Mask box still active, click and drag on the canvas over the cheek area of the subject’s face.
10. Click the “Texture” layer box so that it is active (not the Vector mask).
11. Set the Opacity for the “Texture” layer to 50%.
12. “Texture” layer still active, goto Image > Adjustments > Color Balance. Adjust the RED sliders to the right for Shadows/Midtones/Highlights. This will give the texture a redish tint, so that it looks more like a rash or ugly skin disease.
13. Finally, goto Image > Adjustments > Hue/Saturation. Move the Saturation and Lightness sliders to the left so that the texture blends better with the subject’s face.
14. You should now have your skin disease effect.