Here is a photography trick I have wanted to try for a long time where you alter the shape of the ‘bokeh’. “Bokeh” is a loose term used to describe certain out of focus elements in a shot. The shape of the bokeh comes from the diaphragm of the lens when the aperture is open to expose the image.
You can alter these shapes by covering the front of the lens with something opaque that has a shape cutout in it. In this case, I chose a star, but you can do pretty much any shape. It would be a lot easier if you also cut the outside of the filter to the shape of the lens barrel and taped it on, but in my case I was lazy so I just held it in front of the camera.
Of course doing this will also significantly darken the edges of the frame. And the effect will only apply to points of light that are out of focus, not all objects. And nothing that is in focus will be affected.
I’m not really sure if this trick has much use, but it was kind of fun to play around with.