This series is a little different from the others in that it is more of a tutorial on how to use various apertures, and how the lens draws, particularly with respect to vignetting behavior, but in general the combination of all effects (“the sum of everything”).
Apertures f/2.8, f/4 and f/9 are used (only those three) in order to make the differences as clear-cut as possible (without the distraction of all apertures).
Consider the “Goldilocks” depth of field principle: just the right amount of sharpness balanced against just the right amount of blur. Along with the just the right amount of vignetting, particularly if the scene has distracting bright areas in peripheral areas of the frame.
Images up to 24 megapixels at all three apertures, along with large crops.