This clever device has been designed to utilise the flash emitted by the external flash units on Nikon & Canon cameras. It is virtually foolproof having no circuitry of its own & therefore requiring no power source. Instead light from the main flash passes through a series of internal mirrors to spread the light evenly around the subject to provide virtually shadow free illumination that is controlled by the cameras TTL sensors.
It is easy to fit as shown in the accompanying images. Slightly cumbersome it is best used with the camera mounted on a tripod for support & this may limit its useability in a field situation, however it has no other disadvantages that I have been able to identify. This unit was obtained on eBay for a post paid price of $25 from a Chinese supplier & took approximately 4 weeks to be delivered.
I do not have a macro lens so have only been able to use the O-Flash for close up work & have been pleasantly impressed by its performance. The sample picture of a Yar Dragon figurine that is approx 7cm high was shot at f16 from a distance of 45cm with a 17-80mm lens on my Canon 550D with a 420EX flash.
O-flash is cheap and will fit most flash units. It allows the camera—flash combination to adjust the light intensity through TLL metering.
The Down side—
Although O-flash fits most flash units, the fit may be tight and the ring is not perpendicular to the axis of the lens. Some reviewers have found the light may have a mild blue cast. The biggest pitfall is that there may be a 3 stop drop off in light intensity making it difficult to use for portrait work. (As opposed to the more expensive Ray-flash with only 1 stop drop off)
A ring flash, invented by Lester A. Dine in 1952, originally for use in dental photography, is a circular photographic flash that fits around the lens, especially for use in macro (or close-up) photography. Its most important characteristic is providing even illumination with few shadows visible in the photograph, as the origin of the light is very close to (and surrounds) the optical axis of the lens. When the subject is very close to the camera, as is the case in macro photography, the distance of the flash from the optical axis becomes significant. For objects close to the camera, the size of the ring flash is significant and so the light encounters the subject from many angles in the same way that it does with a conventional flash with soft box. This has the effect of further softening any shadows.
Ring flashes are also very popular in portrait and fashion photography. In addition to softening shadows and creating circular highlights in the model’s eyes, the unique way that a ring flash renders light gives the model a shadowy halo that is a common feature of fashion photography.
There are also passive light modifiers, (O-flash or Ray Flash) which will shape the light from an ordinary (shoe mount) flash into that of a ring flash. The adapters use a series of diffusers and reflectors to “bend” the light in an arc around the lens axis. The light is then emitted from that arc. This maintains any through-the-lens (TTL) lighting functions that may be shared by the camera and flash, as the actual light source has not changed.
Ring flash as a lighting technique has enjoyed a strong resurgence over the last few years, as photographers realize that it is far more useful than the one-look way in which it has been used for decades. Specifically, it is now being used primarily as a fill light to raise the illumination level of shadows created by other, off-axis lights. It is considered to be a particularly good source of fill light, because it does not create harsh shadows.