Think of the convenience to have all your favorite "Best of" looks, right at your fingertips.
Here are a few additional reasons why we feel this is a good practice...
1. It's a great way to present your portfolio along with various options to a client, and having them chose the look of the end result, giving them the sense of participation, and then easily reproducing the EXACT same lighting they chose.
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There are a few systems that work online, but personally, I prefer the type that you download a .PSD file and work in Photoshop.
1. http://www.lightingdiagram.com/