This is a splitting off of my D4S/D4 lantern diffuser project, this branch will focus solely on the D4 size diffuser which I am now simply calling a medium size universal diffuser since it has adapters to fit most common lights. I still have my other diffusers available which you may find more useful for your application. The main diffuser is 28mm inside diameter, meaning any light up to that size in diameter can be used. If you need an adapter for a specific light, just ask and I'll upload one!
The medium universal diffuser aims to turn a flashlight into an effective area lantern by smoothly diffusing and refracting light in all directions. In a sense, we are trying to move the light source from inside the flashlight tube, to the center of the diffuser. I use a system of diffractors built in to the lantern in order to scatter and bounce the light in the center of the reflector, causing far more light to escape out the sides and in more directions than a simple tube or silicone sock diffuser.
This project is passively ongoing and I will occasionally update the design or add an adapter or other gizmo here and there. So far we have the following:
D4 Diffuser Mk.1 - works well, taller, recommended for lights that throw a more concentrated spot, single emitter+reflector lights, not recommended for the D4 or FW3A but it would work.
D4 Diffuser Mk.2.5 - best yet in terms of efficiency, recommended all around especially for the D4 and FW3A. Height above the light is about 62.5mm.
Stability Stand - friction fit stand for the D4 and FW3A to increase stability on uneven surfaces or just when you want to not worry about your lantern falling over. S2+ size lights work okay but they do not sit snug in the base.
24mm S2+ Step Up Ring - an adapter ring for 24mm diameter lights.
25.5mm FW3A Step Up Ring - an adapter ring for 25.5mm diameter lights.
Update July 10, 2019: Replaced Mk3 diffuser with Mk2.5, closer to the Mk2 design and has fewer artifacts.
Taller layer heights theoretically let more light pass through, but I've had good results right around .16mm. White filament works but you lose light and depending on the filament it can be an ugly tint. Colored translucent filaments look really cool.