Canon flash manual mode and distance

Started Oct 6, 2013 | Discussions thread
WFulton Senior Member • Posts: 2,695
Re: Canon flash manual mode and distance

BAK wrote:

Nothing in this thread makes any sense, except the first question.

Well, if you had a Nikon flash with the GN mode discussed in the book mentioned, you would understand the question.

Yes, speedights have many Guide Numbers (not mentioned in any way by this book however). The book only mentions using GN mode (without knowing anything more).

The flash does already know ISO and aperture and zoom (via hot shoe communication, or one could enter ISO and aperture and zoom for an off-camera flash). And these flashes also know the full GN chart details (likely the base formula).

So in Nikon's GN mode (on the higher end current models), you simply enter the direct flash distance, and then it knows how to set flash power level for the situation. It is quite accurate too, and since it is independent of the subjects reflectivity, is also more consistent than TTL. But it is direct flash only, and you have to know the actual distance. And you have to have a flash with GN mode on it.

So TTL still has many advantages too, but the book does not cover TTL. The book has some good strong points, but proper exposure of manual or TTL flash is not in there, except for GN mode if available.

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