Archived posting to the Leica Users Group, 2002/01/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]On 1/14/02 1:21 PM, "Rolfe Tessem" <rolfe@ldp.com> wrote: > Let me clarify the comment on TTL flash. It is true that several > manufacturers allow multiple units to be hooked up and triggered > simultaneously, while having exposure controlled by the camera's TTL > circuitry. The one I'm most familiar with is Quantum. > > But all this buys you is the assurance that you will get a correct > exposure on the film. The TTL stuff knows nothing about what kind of > ratios you want between and among the various flash units. So how do you > regulate the ratio? With all of them I'm familiar with, you have to > physically position the units so the ratio will work out properly (one > unit twice the distance from the subject as another, for example), since > the TTL circuit is going to squelch all the units simultaneously once it > senses that enough light has reached the film. If you're going to go to > that kind of trouble, you may as well just use the units in manual, > position them where you want, and meter the scene. > > As far as I know, and I'm pretty sure about this, as I've described it > above is how all the systems you mention work. Which is why I said that > TTL flash metering is really only of utility when using a single unit. > And I didn't say it was *just* for wedding photographers; I stated my > opinion that it was probably designed with their needs in mind. Rolfe: You should have a look at the Canon E-TTL system. Their system allows you to have full wireless flash capabilities AND do ratioed A:B lighting up to 1:8 or 8:1 in 1/2 stop increments automatically. - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html