Flash TTL metering + camera metering mode = ?

[naheuy]

hi guys/ladies,

i just got my hotshoe flash a while ago, and i am quite in doubt over something which is happening. my composition technique is the one whereby i use the centre spot to AF, then recompose and press shutter. i use manual mode btw so everything's fixed

but sometimes, when i do that, i get really underexposed pictures (especially when using fast shutter) or whiteout subjects. so i was thinking, does the camera metering and the flash unit's TTL metering work independently? (i.e. when i recompose, the ambient light component doesnt change, but the flash unit's TTL metering will meter the new 'centre' and meter off that instead, making it undesirable)

if thats the case, whats a plausible solution out?


thank you!

 

[brapodam]

Either move the AF point such that it is on your subject, or use manual flash exposure. I believe flash TTL is not smart enough to know what is your "subject", and just meters off your focus point.

 

[Octarine]

Every camera system has its own specifics for metering and flash. Your profile states a Sony A230. Maybe you should ask the question in the Sony subforum?
In general: ETTL Metering for flash and exposure metering are two different things. Exposure metering is done the moment you half-press the shutter. Depending on your settings (metering mode) the camera will find an exposure setting matching your conditions. ETTL for flash is done just before the picture is taken, using a low intensity pre-flash. The incoming light is measured and the flash for the real shot is adjusted accordingly. Usually this is done for the foreground subject and depending on camera maker and model this ETTL metering can be done on center or any other point of the frame (Your manual will tell you more). Obviously, if the camera uses the center of the frame for ETTL measuring and your subject isn't there after you recomposed the image the results can be anything.

 

[daredevil123]

From what I read, TTL meters center weighted only. If you have off center subject you need to use FV lock with the subject in the center of the frame. Remember to release the FV lock after you are done shooting in that composition.

Read up in your flash and camera manual on how to use FV lock.

And yes, flash metering and camera metering are separate, at least in Nikon.

 

[naheuy]

hi brapodam, Octarine & daredevil123,

thanks for your replies! ill be more specific in the sony threads afterwards, meanwhile this will help me get a workaround somehow if i want to (severely) recompose my subject to say, a corner of the frame.