Mix of TTL and Manual flashes
InsuredDisaster
Registered Users Posts: 1,132 Major grins
I have a question that I hope you might be able to answer. I'm interested in some of the inexpensive Chinese flashes, but the task I need them for involves rapidly varying flash to subject distance. I'm hoping to increase the number of speedlights to increase maximum power and improve recycling times as well as increase some flexibility.
My question is this: If I use my SB-800 to trigger the Sb-600's via CLS-TTL, and have the manual flashes set to a given level, will the TTL system increase or decrease the TTL flashes as needed to balance out the light. ie, subject moves further away, manual flashes remain on say 1/4 power, but the TTL increases to 1/2 power, then as the subject moves closer, the manual flashes remain on 1/4 power but TTL based flashes drop to 1/16th power?
The optical triggers supposedly ignore monitor preflashes and I'm not really concerned about actually triggering them, just how the TTL based flashes would perform in this setup.
My question is this: If I use my SB-800 to trigger the Sb-600's via CLS-TTL, and have the manual flashes set to a given level, will the TTL system increase or decrease the TTL flashes as needed to balance out the light. ie, subject moves further away, manual flashes remain on say 1/4 power, but the TTL increases to 1/2 power, then as the subject moves closer, the manual flashes remain on 1/4 power but TTL based flashes drop to 1/16th power?
The optical triggers supposedly ignore monitor preflashes and I'm not really concerned about actually triggering them, just how the TTL based flashes would perform in this setup.
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Comments
I think what you ask is a very good question, and one if I had, I'd simply try it to find out the answer. I have used the CLS system pretty extensively, but I've gotten away in the last year or so from using TTL. From what knowledge I do have, I'd say yes if the lights are aimed at the subject and that subject is what is giving the CLS feedback to lighting. But somehow I cannot imagine such a perfect world.
I say try it out! You don't need the other flashes to see if TTL is going to react.
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Correct. In modern dSLR cameras they use the pre-flash information before the main exposure to set the flash output. A modern camera's flash exposure system would not necessarily measure the manual flash exposure contribution at all.
If the manual flash is triggered via a "pc" connection then it will fire during "image capture" but the camera has no way of knowing its contribution of light.
If you plan on using an optical slave then it should be of the "digital" slave variety for contributed flash or the optical slave will trigger during pre-flash. In that case the camera "would" sense the slaved flash contribution but, since it cannot control the manual flash output, the exposure will be uncontrolled and unpredictable.
If you use a remote flash with an "auto" capability then that flash will control its own exposure contribution via its own sensor and the flash settings.
Bottom line, mixing manual flashes and TTL flashes is rarely beneficial and the only time I have used that combination purposely and successfully is using the TTL flash(es) for primary/key and fill light and then using a manual flash for either rim/hair and/or background light.
For the original poster's application I would go with all iTTL flashes and use (at least) 2 groups to allow different flash settings by group.
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It is actually TRUE TTL....the new digital cams still read "thru the lens" - ttl.........