Custom bokeh experiments

DrLex · May 18, 2023

Inspired by one of the challenges at DPR, I started experimenting with manipulating the bokeh.
I have a 3D printer, so I can generate things of pretty much any shape (within certain limits). Knowing that taking photos through fine grids or curtains will often cause unusual effects, I modelled and printed a special grid that has lines at 120° angles. The cleanest print is obtained by superimposing 3 layers that have their lines going in a single direction, this makes it much easier for the printer which otherwise would have to print a lot of tiny triangles which produces a messier result.

OnePlus AC2003
ƒ/1.75
4mm
1/50s
ISO 250

Mounting this grid in front of a lens while it produces a pronounced bokeh, will result in the bokeh being distorted in an interesting way, with edges near multiples of 60° angles being accentuated and repeating in a diffraction-like pattern. It works best when focusing sufficiently far away, otherwise the grid itself may start to become visible in the photo. The size (scale) of the effect grows with increasing distance between objects in focus and out of focus.
It does seem some sharpness is lost, probably due to diffraction, but this technique does open up opportunities for adding a special effect to photos. I might try some other types of grids when I find the time.