Tag Archives: wyant

Aberrated Wave to Image Intensity to MTF

Goodman, in his excellent Introduction to Fourier Optics[1], describes how an image is formed on a camera sensing plane starting from first principles, that is electromagnetic propagation according to Maxwell’s wave equation.  If you want the play by play account I highly recommend his math intensive book.  But for the budding photographer it is sufficient to know what happens at the exit pupil of the lens because after that the transformations to Point Spread and Modulation Transfer Functions are straightforward, as we will show in this article.

The following diagram exemplifies the last few millimeters of the journey that light from the scene has to travel in order to smash itself against our camera’s sensing medium.  Light from the scene in the form of  field  U arrives at the front of the lens.  It goes through the lens being partly blocked and distorted by it (we’ll call this blocking/distorting function P) and finally arrives at its back end, the exit pupil.   The complex light field at the exit pupil’s two dimensional uv plane is now  U\cdot P as shown below:

Figure 1. Simplified schematic diagram of the space between the exit of a camera lens and its sensing plane. The space is filled with air.

Continue reading Aberrated Wave to Image Intensity to MTF