Light beam and GN comparison
We've taken the new Retra Flash and made a comparison of light beam and Guide Number (GN) performance with two popular underwater strobes.
Strobe #1 (left) - Strobe #2 (center) - Retra Flash (right)
All strobes are without light modifiers.
All strobes were positioned 30 centimeters from a white wall and set to fire on manual power settings. With the help of a light meter we were able to achieve the same exposure in the center of the light beam and observe how the shape and intensity changes with angle.
We then compared the GN of all three strobes by measuring the exposure value at maximum power in the center of the light beam at 1m distance and iso100. The first value is based on manufacturer specification of Strobes #1 and #2 which we compared with. The bracketed values are the absolute measurements with our light meter:
- Strobe #1:GN32 (absolute measured GN20)
- Retra Flash: GN30 (absolute measured GN18)
- Strobe #2: GN 24 (absolute measured GN14)
Absolute measurement deviation: +/- 1GN