Want to know what an item's resulting light level will be before you dismantle and infuse it? Here's the math: ([new light level] - [old light level]) * 0.8 + [old light level] Example: Infusing a 270 item into a 250 item (270 - 250) * (0.8) + 250 (20 * 0.8) + 250 16 + 250 Result: a shiny new 266 item Source: https://www.reddit.com/r/DestinyTheGame/comments/3l74nv/infusion_guide_to_infusing/cv3sj3v Edit: There's been some speculation that the quality of the item that you're infusing matters. For example, if you infuse a blue into an exotic, you may get worse results than if you were to infuse a purple into an exotic. This is based on just a few sparse experiences and some speculation, however. If anyone has additional data on this point, please share.