Thermal cut-out: Speedlight SB-900 vs. SB-700

photogreen

My tests show that SB-900 is more prone to overheating than SB-700.

Also, I was kind of surprised that flash zoom affects the overheating. Now that I think about it, it kind of makes sense... I'm guessing, at the wider angles, the bulb is closer to the front reflector, which starts to heat up during the rapid firing... Any thoughts?

Nikon Speedlight SB-700 vs. SB-900: overheating (thermal cut-out) test

ziggy53

At wide-angles the flash is forced to spread the output into a wider "beam", so more flash output is required for the same exposure. A flash with a "zoom" head will always have a higher GN at the longer end as a result.

photogreen

ziggy53 wrote: »

At wide-angles the flash is forced to spread the output into a wider "beam", so more flash output is required for the same exposure. A flash with a "zoom" head will always have a higher GN at the longer end as a result.

You're right, but that applies to TTL. I've tested at full power (manual), so the output was the same...

ziggy53

photogreen wrote: »

You're right, but that applies to TTL. I've tested at full power (manual), so the output was the same...

Ah, gotcha. You instincts may be correct regarding the cause.

Qarik

that's very odd wrt to the zoom of the flash