Sigma EM-140 DG Ring Flash
One popular uses of ring flashes is close-up macro photography. Sigma's EM-140 DG Ring Flash is designed specifically for photographing those small details that make macro photography so captivating. This is also a popular macro flash in scientific and medical fields. Sigma is perhaps best known for their line of adapted lenses and are the most popular 3rd party manufacturer of lens products for Canon, Nikon, and Sony camera systems. Their line of flashes are also offered in multiple manufacturer mounts, including Pentax.
The Sigma EM-140 DG Ring Flash has a guide number 46'/14m at ISO 100, so don't expect it to perform as a powerful portrait flash, but it should give you centered, circular catch lights which is half the fun. For close-up macro work, this flash has the goods as you can flash both of the EM-140 DG's flash tubes together, just one or the other, or you can use them in a ratio to better sculpt the subject with shadow. This ring flash comes in TTL modes for each manufacturer, Canon, Nikon, Sony, and Pentax. As an option, you can have the EM-140 DG to trigger Sigma's EF-500 DG Super or EF-610 DG ST set as a slave for even more light sculpting options.
This flash mounts onto the camera a little differently than the other flash units on this list. By using lens adapters, 55mm and 62mm rings included, the EM-140 DG screws directly onto the lens. Be mindful that if you intend to use this flash on a lens that doesn't have either 55mm or 62mm filter threads, you will need to purchase the proper lens adapter from Sigma or adapt the included rings with a step-up adapter. If you're looking for a ring flash for macro photography, the Sigma EM-140 DG Ring Flash is an ideal choice for snapping those fine details.