When camera lens makers announce new lenses, one of the specs they always tout is how many aspherical elements the lens designs have. If you’re not sure what those elements are and what they do, here’s a short and helpful 4-minute video by Michael the Maven that’ll bring you up to speed.
Aspheric lens elements have surfaces that aren’t portions of a sphere, and this more complicated shape focuses light better than a simple lens, reducing various types of aberrations.
With simple lenses, complicated multiple lens designs are often used to reduce aberrations, but alternatively, a single aspheric lens can be used to replace entire groups of lenses. This results in lenses that are not only sharper but smaller and lighter as well.
“So the next time you’re reading about this great new lens that you’re getting or you want to get, and you see that it has multiple aspherical elements in it, that is what it’s talking about,” Michael says.