Sell 550ex and buy 580????

Started Dec 27, 2006 | Discussions thread
Brian Ripley Contributing Member • Posts: 788
You forgot the inverse square law

Hugowolf wrote:

Were do you get the "50% effective increase in power" from? The
580ex has a stated GN of 58 metres, the 550ex has a stated GN of 55
metres (both at f/1, ISO 100, and 105 mm).

(58 – 55) / 55 ≈ 5.5%

and the power increase is (58/55)^2 - 1 ≈ 11% thanks to the
inverse square law. However, as others have said, that applies
to the delivered light at full tele zoom, and not necessarily to the
power generated: it could be that it covers a slightly smaller area.

When fired from inside a softbox, I can't consistently measure the
difference with a light meter.

The 580ex is much easier to use, the interface is better, the tilt
and swivel is easier, the recycle time is slightly better, and the
batteries last longer.

Brian A.

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