How do you balance flash & ambient light

Joined
Sep 17, 2006
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Hamilton , New Zealand
I read this advice being given all the time, but don't understand what TTL/BL is all about.

According to the sb800 manual, when in TTL/BL mode, "the flash output level is automatically adjusted for a well balanced exposure of the main subject and background". But the flash doesn't illuminate the background, so how can it effect its exposure? It doesn't appear to change the shutter speed, iso, or aperture, which I'd think would be the only ways to effect the exposure of the background.

When I'm shooting flash outdoors, I take control of the background exposure by selecting the shutter speed, aperture, and iso, so I thought the only job left for the flash would be to expose the subject properly, which it TTL.

Would you mind explaining how TTL/BL works?
I was also confused by the manual at first and thought it meant the flash tries to also expose the background . Some people think it is describing ''slow-synch'' type flash - they haven't explained it very well .
Basically from what I understand now is that it takes into account what the camera meter sees as well as the flash meter and doesn't think it is the only light source like TTL seems to do . I tried a few tests with TTL compared to TTL/BL outdoors and the TTL/BL always seemed to fire about 1 stop weaker .
Indoors was a different story and gave some interesting results so I stay with TTL indoors . I still end up setting TTL/BL to -1 outdoors as a personal preference .
 
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Jan 29, 2005
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St. George, Utah
I'm not sure of that, Gordon. Using aperture priority mode, I shot the same scene in in TTL and TTL/BL, and there was no difference in SS, aperture, or iso. All it did was turn down the flash power.

I'll be interested in your test results.
I think you might be misunderstanding what I meant or else I wasn't very clear. I was simply saying that the camera makes the initial setting in any of the auto modes but in M mode you make the settings by zeroing out your meter. The settings may very well be identical but with one the camera controls that and in the other, you do. I do agree that the camera will control the flash power in any of the auto modes when using TTL-BL.
 
Joined
Aug 23, 2007
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Just went through the SB800 & the SB600 Manual and neither one goes into depth at all about TTL-BL and what modes you can use it in or that your or that it works better it your subject is in the center of the frame. I guess they just think we should know.:mad: Not that was my question to start with but I'm learning something new that I didn't know.:smile:
 
Joined
Jan 29, 2005
Messages
33,093
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St. George, Utah
Just went through the SB800 & the SB600 Manual and neither one goes into depth at all about TTL-BL and what modes you can use it in or that your or that it works better it your subject is in the center of the frame. I guess they just think we should know.:mad: Not that was my question to start with but I'm learning something new that I didn't know.:smile:
If you got too smart Debbie you would put the pro's out of business. :biggrin:
 
Joined
Sep 17, 2006
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Hamilton , New Zealand
Frank, I think that in P/S/A mode with TTL/BL the camera sets the exposure for the overall scene and then adjusts the flash automatically to give the best exposure to the subject. The problem is it expects the subject to be in the center and if it is off to one side or the other it does not do all that great. There are ways to overcome that but personally I like to shoot in M with TTL as that way I am in control and have no one to blame but myself if I am off.

I will be interested to hear what Desmond has to say.
My model says it all for me , no it is not underfed or badly treated as some suggest but the skin tones are a bit "plasticky" . I did quite a few comparisons to see the difference between the two and save the results to remind myself later :

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The difference is not as pronounced indoors and I trust TTl more in the tests I did .[indoors that is ]

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Very good examples Desmond. Thanks for posting them!! Debbie
 
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