Understanding MTF Charts
What is the MTF of a lens and how does one calculate it?
Julius Fernandes, Goa
This article was originally published in November 2014.
MTF is an abbreviation for Modulation Transfer Function. It is an indication of optical resolution and helps give you an idea of how any particular lens is going to perform in the real world. More importantly, it provides a comprehensive method for choosing the best lens to suit your needs.
An MTF chart is a graph that is plotted in the laboratory with the help of a resolution chart and scientific apparatus, under standard lighting and test conditions. Every graph chart has two pairs of lines, one that indicates the resolving power of the lens, while the other one signifies its contrast transmitting ability, at any given aperture setting. Resolution and contrast are the two parameters that tell you how sharp a lens is.
However, do note that while an MTF chart is an effective indication of the performance of a lens, it cannot be determined only by looking at this chart. A lens’ performance also depends on other factors like humidity and climate resistance, quality of construction, ergonomics, softening, blurring of colour, aberrations in different lighting environments and other such on-field factors.