The Asiva Selection Plug-In for Adobe Photoshop is similar to the Select->Color Range tool. However, its precision in selecting based upon pixels' color properties is the best transition selection method in the industry. That's because it is based upon patented technology that no one else can offer.
Define the source colors you wish to select using the built in Hue, Saturation and Intensity (HSI) Curves. Sampling the colors in the area(s) of an image you wish to select with the built in Color Sampler Tool is a simple way of choosing these values. Adjusting and fine tuning the curves allows you to include or exclude certain Hue, Saturation or Intensity values selected. This will give you a very precise and natural selection to work with.