MICHAEL ARCHAMBAULT, PETAPIXEL:
"Purchasing a new lens for your kit can be an expensive endeavor and the more information you know before making a purchase is always useful. You may have noticed that lens manufacturer sites tend to include what is known as a Modulation Transfer Function (MTF) chart. These charts help to give shooters a better idea of the glass’ performance, but they’re not the ‘end all’ answer for knowing whether a lens is good or not. Here’s an introductory guide on how to accurately read an MTF chart and how to take their readings into account for your purchase."
Read and learn, here.