Power (actual and GN) and size

Started 9 months ago | Discussions thread
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Sympa Senior Member • Posts: 1,341
Power (actual and GN) and size

I'm now owner of two flashes - the Godox TT350 and TT685 respectively.

The TT350 has a GN of 35 meters at 100mm zoom. The TT685 has a GN of 60 meters - but at 200mm zoom!

Now I'd think that the illuminated area is roughly equal at the respective zoom settings and distances. Which makes me wonder why the TT685 is so massive when compared to its smaller brother. Is this because the zoom doesn't affect all the light? Or because the bigger flash lights more even, needing more energy to get the center at the correct brightness?

Any ideas about this? The big falsh is twice the weight of the small one, so I'd expect the actual power output in wattseconds to be double as well... which is 1.4 times the GN. With the zoom that should then be 2.8 times GN, right?

 Sympa's gear list:Sympa's gear list
Sony RX100 Sony Alpha NEX-F3 Sony a6000 Sony E 50mm F1.8 OSS Sony E 55-210mm F4.5-6.3 OSS +8 more
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