Many surface mount components can be soldered without any magnification, or the 2-3X magnification provided by common light / magnifying glasses on booms. But when you get down to .8mm or .5mm pitch, more magnification becomes crucial for ensuring sufficient solder was placed on the components, and that there are no small bridges. A 10X loupe is perfect for inspecting very small pitches without the need of an expensive microscope (It’s also the recommend power for inspecting jewelry). Note that a microscope is nice if you do a lot of SMD soldering since you can watch what you’re doing under magnification, whereas a loupe can only be used to check your work. If you do get a microscope, get a stereo zoom one with at least 30X magnification and the largest working distance possible. To use, hold the large end against your eye and the small end an inch or two away from the joint. This loupe can be held hand-free by squeezing the big end with your cheek and eye-socket. A note about diopter vs. magnification power: There are two formulas typically used to convert between magnification power (M, how much larger an object looks) and diopter (D, a measure of focal length). M = D/4 and M = D/4 + 1 (depending on manufacturer) Here’s a reference.