Select a Modifier

Ringflash Expected Output
Wattseconds Expected Output
at 10 feet (ISO100)		 Expected Output
at 5 feet (ISO100)		 Guide Number
(ISO100)
Full 320 Ws
-1 160 Ws
-2 80 Ws
-3 40 Ws
-4 20 Ws
-5 10 Ws


Notes on Expected Output:
These output readings have been measured with a Sekonic L358 flashmeter set to 1/125 second shutter speed at ISO 100, placed 10-feet and 5-feet from the flashtube for direct reflector specs. Readings were taken in a 14-foot x 14-foot room (with an average ceiling height of 14-feet) with both the walls and floor painted grey. Please note that readings may vary when taken in other environments and with other meters, as different brands of flashmeters can vary in their interpretation of correct values.

Notes on Guide Numbers:
The Guide Number (GN) is a standard measurement serving to indicate a flash unit's output by calculating the distance times the f-stop, with respect to the film speed (GN = f/number x flash-to-subject distance). This term is not wholly reliable for comparing flash units because it relates more to the angle of the reflector than to the actual amount of light produced. For example, a flash unit with a given amount of light output will register a much higher guide number (f-stop at 10') if it has a narrow angle reflector (for telephoto lens) than if it has a wide angle reflector. But the actual amount of light is the same in both cases…it just covers more area with the wide angle reflector (at a lower guide number). Studio flash units are designed to be used in many different configurations, with different accessories. The angle of coverage will be different in each case as will be the achieved guide number for a given amount of emitted light.