Cue the Cubes!
Again??? Well, yes. I do these blog posts for myself as much as for my readers. They are my public notebook of lighting tests and experiments.
Here we have three exciting and vibrant still life studies in gray. All three photos were made with the Interfit Deep Zoom Reflector on their Badger Unleashed strobe head. The image on the right was with the bare reflector. In the middle I added the included diffusion sock, and on the left I added an additional layer of diffusion (double-diffused as some might say). I have identified three places in the images to look at and compare.
At point one I want you to look at the primary shadow of the gray cube onto the white cube (scroll down to the bottom of the post for larger versions of the cube photos). With the open reflector there are actually multiple overlapping shadows. The open reflector is not even across. There are multiple light sources: the flash tube, the glass dome, the walls of the reflector. Each is slightly different in brightness and casts its own shadow. Adding a diffuser homogenizes the light into one large source and eliminates the hot spot. You can see this in these photos of the face of the reflector.
Looking closely at the cubes you should still be able to see that there is a primary hard edged shadow at point One and that doesn’t change between the three photos because the overall size of the light has not changed. Remember, for a light to be softer with more gradual shadows the light has to come in from many directions. Once you have added a diffuser it won’t matter how many extra layers you add, it will not make the light any softer. The diffusion will alter the contrast of the scene as it spreads the light out in a wider pattern allowing it to bounce off of items in the environment such as the floor, walls, ceiling, etc. filling in the shadows and making them less dense. Less dense = less contrast. But the shadow edge, the quality, does not change.
Point Two is similar. The open reflector shadow is deeper. Adding the diffusion evens out the light from the reflector and fills in some of the shadow. But again the primary shadow edge is about equal.
Point Three is the most dramatic difference where the diffuser made the light larger and able to wrap around the side of the black cube to provide more illumination so you can see the back of the table top.
What I really want to concentrate on are the differences between the images with single and double diffusion. Or is differences the wrong word as they are actually very similar, almost identical in appearance. The main difference being that I had to open up the aperture a stop to maintain the proper exposure.
I hope this helps show that adding more and more layers of diffusion will not soften the shadows in your photographs. That comes from making the light larger. Multiple layers of diffusion require more light output or allow you to cut down the amount of light if you cannot power it down or don’t want to change your f/stop.
Click on each of the photos below for a larger version.