Re: Flash compensation range scale on SB24 [v04.n202/2]

[Art Searle]

Krisada wrote:

I am wondering if someone can help explain...

Why when I set the compensation of the SB24 say to -2EV
(or any negative numbers), the range indicator on the back
of the SB24 increases to greater distance? I was expecting
it to be less distance if -2EV means I want 2 stop less
light from the flash. Is something wrong with my SB24?

Nothing is wrong with your flash.  If you set -2 EV compensation the amount
of light emitted by the flash will be less as controlled by the TTL
circuitry but the distance that the flash can be used and still work 2 stops
below the non-compensated output level will be twice as far.

A -2 EV change in flash exposure is exactly 4 times less light than no
compensation at all.  Using the inverse square rule, the flash will have
exactly twice the usable distance at -2 EV.

Example:  If your flash has a maximum usable distance of 10 feet at a given
f stop and film speed, setting -2 EV will reduce the output of the flash at
10 feet by 2 stops. However the flash's maximum usable distance for -2 EV
will be 20 feet.

Art

Art Searle, [EMAIL PROTECTED], Lake Grove, NY, USA
20 miles east of Nikon USA www.erols.com/w2nra

Re: Flash compensation range scale on SB24 [v04.n202/2]

[John Bean]

Negative compensation means you want less light on the subject - so for any
given output, the subject must be further away. Using TTL, the output of
the flash will be reduced to compensate, but a limit is reached when the
flash is at full output. In this case, it will be capable of illuminating a
subject which is further away (twice as far for your example -2EV) than
with "normal" illumination.


Regards

John Bean