This post describes a simple flash diffuser solution I've been using a lot lately as a complement to my regular beauty dish style diffuser. The basic concept is nothing new: the diffuser is attached to the front end of the lens and wraps around the subject creating the equivalent of a small light tent.
This type of diffuser is sometimes referred to as "cup diffuser" since the main component is usually some sort of white plastic cup (Stephen was the first I saw describing this idea so I consider him to be the inventor).
Besides giving an extremely even and soft light this type of diffuser has another benefit since it makes it easier to get a well exposed background. A common problem with flash macro photography is that while the main subject is easy to expose properly, the background – being far away from the light source in relation to the foreground – becomes relatively dark or black (and if you expose for the background the main subject is over exposed or blown out). This becomes less of a problem with cup diffusers since the diffuser also acts as a shade, reducing the intensity of light hitting the main subject and thereby compensating for the fact that it's much closer to the light source than the background (which is lit by light coming from the flash directly).
I've been using this type of diffuser for at least a year or so but there are a couple of things that I've found inconvenient:
• Different lenses need different ways of mounting the diffuser. If it
has a good fit on one lens, chances are it will fit badly on other
• Switching between diffusers is fiddly. I often want to be able to quickly switch between this type of diffuser and a beautydish style diffuser attached to the flash (better for skittish bugs and sometimes gives a more dynamic (less flat) light).
• Closely related to the previous point: mounting/unmounting the diffuser takes time. You either have to pack the gear with the diffuser attached (which often takes a lot of room in the camera bag) or spend precious time in the field mounting/unmounting it. And of course moving the diffuser from one lens to another becomes troublesome to the point where it might even put you off switching lenses.
• As you use this type of diffuser in the field they are often subject to quite rough treatment. Some solutions I've tried has worn out in a few hours.
The solution I've arrived at works by using several different small mounts, customized for each lens but with a standard fit for the protruding "light tent" part (referred to as the tent from now on). The mounts can be left permanently on the lens without interfering with different types of diffusers or making packing the equipment difficult. With the mount in place the tents can be mounted/unmounted using one hand in the matter of seconds. It's also very easy to make new tents if the old get worn or if you want a smaller/larger or differently shaped one.
Obviously this idea can be implemented in many different ways and the one I'm showing here is just one that happened to suit my needs in terms of size, diffuser material properties and availability.