Value correction

= Value Correction = Value correction is a texturing method that allows you to remove problems in value variation from a source image. This is a common problem when trying to create tiling textures, and is often due to uneven lighting in the source image.

Lab Color Technique
The following Photoshop technique will help you remove value variation but retain the hue variation.

Note: This is useful for removing contrast, but some of that contrast is good to have and you may not want to remove it all. Experiment with keeping a copy of image that hasn't been equalized in this way, and masking contrast back in only where you want it. For instance, you could make a value-equalized version and paint it in only over the seams you are trying to remove.

Original thread: http://www.polycount.com/forum/showthread.php?p=1169603#post1169603