430EX question

Started Feb 5, 2013 | Questions thread
OP ihgold2 Forum Member • Posts: 71
Re: 430EX question

No, the flash has no way of knowing which distance it can be used at, when it's a slave flash. The calculation it does when it's mounted on the camera does of course require that the flash is able to light up the part of the subject which faces the camera. For all a slave flash knows, if may be aimed so that it doesn't hit the main subject at all, in which case the distance has no meaning whatsoever. The flash may be used to lift a shadow you want brighter, in the background, instead of providing light for the main subject.

But if you do place the slave flash in such a way that it more or less illuminates the surface of the subject that's facing you, then the same distance applies as if the flash was on the camera. The flash just can't know, so it can't compute it for you.

Thanks again.  My confusion was that, even as a slave, I wanted to be in Manual on the flash.  I want to decide what the flash's "subject" is -- even if it's not the same subject as the photo.  For example, what if I'm using ambient light for my true subject, and I want the slave flash to illuminate something in the background?  If flash power is a function of aperture, distance, and ISO, it seems like I should be able to key in those values on the flash to get the appropriate flash exposure.

Anyway, I'll keep reading and learning 

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