>>3388837Attach the custom bokeh to the front or rear of the lens and open the lens as wide as possible. Then have something like xmas lights or other sharp points of light in the background. Then unfocus the camera so it is focusing in front of the background. Keep doing that until you get the size of hex-bokeh you want. After that, point the camera down slowly and see what distance that is that comes in focus nearer to you. Then you'll know the best distance to get that specific size bokeh. Focusing closer or further away will make it smaller or larger. The faster the lens is the better this effect will be, but you can do it with kit lenses when the aperture is wide open and using shorter focal lengths to make sure it is wide open.
You are basically making a second aperture that is blocking light. So remember that when you are judging ISO and exposure times. Use a tripod to make things a bit easier when testing.
>>3388922>all background looks bohek blurryYou may find that you need to be pretty close to something to get good effect. It will depend on several variables. Like in the OP the pine cone is probably being held in the photographer's hand at relaxed arm length. If a front bokeh isn't working, take the lens off and tape it to the rear, just make sure to not cover anything important and to cut it out just big enough to cover the lens. Don't get tape on the lens, it can be a bitch to get the gunk off! I do rear lens DIY bokeh still for anamorphic filter bokeh and glare with a cat's eye hole and some fishing line.
Here's a square bokeh for a custom lens I made. It slide in behind the lens.
