you will need :
- One large aperture lens (a Canon 50mm F1.8 is used here)
- One sheet of black paperboard
The Diameter is made so that it fits on the lens.
In the middle of the filter the wanted bokeh shape is cut out.
I’m not sure how big a hole the shape can be. But you can check it right away by just looking through the viewfinder.
On the 50mm lens @ F1.8 a 15mm heart gives a metering value equal to F3.2, so it can probably be a little bigger.
The lens must be set to its lowest aperture value (completely open).