Flash distance reading?

[ajbalazic]

I'm having a hard time understanding the distance scale on my flash (EF-500 DG Super)...

Settings:
M, 1/200 sec, f/3.2

Using flash as Fill-In
When the Flash Exp. Comp. is set to

+1 scale reads 18m/60ft
+1 1/3 scale reads 13m/40ft
+1 2/3 .... 9m/30ft
.
.
+3 .... 4m/15ft

Since the flash output is higher, shouldn't the scale read higher (flash reach) and when the flash output is lower, shouldn't the scale read lower.

What am I missing?:o

[Jim M]

I don't have that flash and am not at all familiar with them, but what I think it's telling you is the maximum distance at which you can get the effect you are after. Flash exposure compensation doesn't increase the capacity of the flash; it only increases the exposure. The distance at which you can get that increased exposure decreases because the flash can only put out so much light at maximum power and if you need more light, the light has to be closer. So what that distance reading is telling you is that at the given ISO and aperture, you can get a +1 exposure at any distance up to 18m/60ft. You can get a +1 1/3 stop over exposure at any distance up to 13m/40ft. Any farther away and the flash can't put out enough light to give you the additional exposure you asked it to give. The more additional exposure you ask it to give, the shorter the distance will be when it reaches the point that it can't give you any more light.

[Wilt]

It is showing the max flash distance, assuming the current power setting of the flash, and the currently selected f/stop on the lens (or the f/stop set on your flash, for Auto flash without electronic feedback of lens aperture to the flash)

[ajbalazic]

That makes perfect sense. The scale isn't telling me the flash reach, but the result of exposure up to distance x. Thanks guys.

[Wilt]

That makes perfect sense. The scale isn't telling me the flash reach, but the result of exposure up to distance x. Thanks guys.


It is telling you the reach at the selected aperture! It is not telling you the reach if you used the largest possible aperture, unless you set that aperture.