Specularist
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 p.1 #12 · Has anyone heard of LumoPro Flash? | |
My only point is that the guide numbers can be misleading if read casually, because they depend on several factors beyond flash energy output. This is no doubt obvious to you, but it might not be obvious to everyone.
For example, for the SB-900, Nikon states:
"The SB-900 guide numbers differ depending on the camera's image area, illumination pattern, ISO sensitivity, zoom position and flash output levels."
Only the last variable (flash output level) is "power" as we normally think about it. If you dig deeper you'll see Canon's stated guide number of 58 metres at ISO 100 for the 580EX II (quoted earlier in the thread) is specified with the built-in reflector zoomed to the 105 mm position. Nikon's stated guide number of 34 metres at ISO 100 for the SB-900 is for the head zoomed to the 35 mm position, on an FX camera, with the standard illumination pattern selected. Therefore we can't directly compare the guide numbers of 58 metres and 34 metres, in this case.
By extension, we might not be able to compare the LP160's guide number to the others.
Incidentally, a more direct comparison between the 580EX II and SB-900 can be found in their respective user manuals. The Canon has a guide number of 28 metres at its 24 mm zoom position, which compares to 27 metres at 24 mm for the Nikon with the standard illumination pattern (with other illumination patterns it's a bit more or less).
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