In the last few years, MTF has become a buzzword in both cine and HD lens circles, but there is still a lot of confusion about just what it is, what it can and can’t do, and what it means to the cinematographer in a practical sense. In this article, I will attempt to clear up some this confusion by explaining what MTF means from a technical standpoint.

You may already know that MTF is an abbreviation for Modulation Transfer Function. MTF provides a way to objectively measure image sharpness in a practical and repeatable way that also correlates well with subjective perceived image sharpness.

The smallest practical unit for measuring image detail is a line pair, which is a black line and a white line, side by side. The measurement is line pairs per millimeter, and not lines per millimeter. It is very important to note that we are always talking about a black and a white line pair, and we are counting them as one line pair (1 lp/mm). In the digital realm, we need at least one pixel to represent the black point, and one to represent the white point. So we need a minimum of 2 pixels to image 1 line pair.

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