The ABR800 Ringflash Specifications

Wattseconds / Lumenseconds / Guide Numbers: Quantity of electrical energy is measured in Wattseconds (Ws), also known as Joules. This rating defines the amount of electrical power discharged with each flash. The actual amount of light (Lumenseconds - Ls) produced for a given number of Wattseconds can vary, depending on the efficacy of the unit or system. In particular, older "box and cable" systems, in certain configurations, often produced considerably less usable light per Wattsecond than do highly efficient systems. In other words, a highly efficient modern 160 Ws unit might yield as much usable light as an older or poorly designed 400 Ws unit. This disparity gave rise to the adoption of the informal "Effective Ws" term by some manufacturers of highly efficient units. The Effective Ws term is currently discouraged by most professionals due to its arbitrary nature. Most modern units and systems from reputable manufacturers now offer similar efficiency factors and may generally be compared with reasonable confidence on the basis of True Ws - but there still remain certain low efficiency systems which will boast a high Wattsecond rating yet deliver less light than one might expect.

The specification that should be universally used is "Lumenseconds" as this term is the only one that actually describes light output. In the absence of this term being widely adopted, the best comparison available to the photographer is the measured output with specifically defined real-world accessories.

Regarding the common misconception that Guide Numbers are a good basis for comparison, this is more affected by the angle of the reflector used than by the actual usable amount of light available, and is of essentially no value to the studio flash user. For example, a given studio flash fitted with a narrow 50° reflector will yield a much higher guide number than the same flash fitted with a wide 80° reflector, yet the amount of light emitted is the same in both cases.

Flash Duration (t.5 method – the industry standard for expressing flash duration is referred to as "t.5"): This term defines the length of time it takes for 50% of the total light to be emitted from the flash. Many users confuse this with the exposure time setting on the camera, but they are not comparable specifications.

The light output of a studio flash is not a sharply defined on-off function like the camera shutter. Instead, the light intensity trails off after firing the flash as shown in the graph. The light does not suddenly shut off at the t.5 point but continues to diminish over time. As can be deduced from the graph, a flash duration of, say, 1/1000 second will not stop action as cleanly as would a camera shutter speed of 1/1000 second. A more usable figure for determining the stop-action capability of a flash system would be approximately double the specified t.5 flash duration (approximately 1/500 second for the "t.5 = 1/1000 second" example given).

Sync / Trigger Voltage: When using digital cameras, it is best to check on the maximum sync voltage allowed for your specific camera. Some brands of flash units have sync voltages much higher than ours, some as high as 400 Volts that can damage digital cameras. The sync voltage on all of our AlienBees flash units is under 6 Volts, safe for use with digital cameras.

Typical Output Measurements: Typical Full Power exposure at 10 feet (ISO 100) with the standard reflector is approximately f16 at a coverage angle of 80°. Please note that readings may vary when taken in various environments (with various room sizes and conditions) and with various flashmeters, as different brands of flashmeters can vary by as much as 1 whole f-stop in their interpretation of "correct" values.