Today it seems that resolution has become one of the most important parameters when choosing our digital camera. Surely many of you have heard of the MTF.
The MTF (Modulation Transfer Function) is just a mathematical tool that allows you to measure the resolution of a camera. It is based on the ability to resolve or differentiate lines at a certain spatial frequency.
To understand the concept of spatial frequency in a simplified way, let’s assume that low spatial frequencies are equivalent to very separate repetitions in space (for example, very separate lines) and that high frequencies are equivalent to more compressed repetitions (very close lines). We must also consider that there is an upper limit beyond which more details can no longer be distinguished, called the Nyquist frequency.
But it is not the purpose of this article to enter into technicalities, quite the opposite: to try to clarify, in a colloquial way, what this MTF is for:
The most classic method of comparing resolution is to do it with the naked eye. However when comparing 2 photographs, there comes a time when the human eye can no longer ‘discern’ more detail, even if we use a magnifying glass.
In order to better compare by means of a mathematical tool, a detail value is taken at an intermediate point between what the eye can discern and the limit of the resolution, this value corresponds approximately to a 50% drop in the MTF, and therefore it is usually called MTF50.
At this point, it should be clarified that resolution is a very important factor, but it is only a part of Image Quality, it is also determined by other factors such as: Noise, different types of aberrations, dynamic range, etc.
Therefore, Image Quality is complex to measure, so let’s remember that in MTF Testing it aims to measure RESOLUTION and not Image Quality. Logically, the more resolution we have, the more we contribute to a better Image Quality, in the same way we do it, the less noise we have.
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