Have I the concept correct

When using your camera in manual, and your flash in ETTL, if you set up your speed and aperture as required, when you focus on a person is it better to have the camera on spot metering (assuming the spot is on part of a persons face) as opposed to evaluative? I know in manual the camera controls are as you set them but does the metering have an input into the flash burst when in ETTL mode? thanks

when you have the camera in M mode, the metering pattern doesnt really matter to the flash exposure. ETTL uses an evaluative or averaging function to select how it determines exposure and doesnt rely on your camera metering settings. The camera metering pattern could affect how you calculate the ambient exposure for the areas not illuminated by the flash though.

Keep in mind when you use flash, you are essentially calculating two exposure values. The flash value and the ambient. At lease for scenes where there is ambient showing. Once you get a grip on that, it will help you understand that changing the base exposure for the ambient can radically change the look of an image by using the ambient to balance the flash, or perhaps use ambient control to put a greater emphasis on the subject.

gonzogolf wrote in post #15205141
when you have the camera in M mode, the metering pattern doesnt really matter to the flash exposure. ETTL uses an evaluative or averaging function to select how it determines exposure and doesnt rely on your camera metering settings. The camera metering pattern could affect how you calculate the ambient exposure for the areas not illuminated by the flash though.

Thanks gonzogolf

jaomul wrote in post #15205168
Thanks gonzogolf

Just added some more theory stuff to my post, not sure if its helpful or not.

It does help. I was allergic to using flash until I bit the bullet and started. I am in the feotal stages but when it works I realise that it can be a great tool. Practicing and learning and probably the odd question here will be the way I will go for a while yet

As gonzogolf explained, the camera exposure and flash exposure are metered and calculated separately. When using ETTL flash exposure, as he also notes you can select either evaluative or average in the camera's flash control menu. Generally speaking, evaluative will be better to use for fill flash, and average will be better to use when the flash will be the primary or only lighting. You may need to use flash exposure compensation in either case to get the exact flash exposure you want.

Then if you use FEL, you get spot metering for flash exposure as well.

stsva wrote in post #15205522
As gonzogolf explained, the camera exposure and flash exposure are metered and calculated separately. When using ETTL flash exposure, as he also notes you can select either evaluative or average in the camera's flash control menu. Generally speaking, evaluative will be better to use for fill flash, and average will be better to use when the flash will be the primary or only lighting. You may need to use flash exposure compensation in either case to get the exact flash exposure you want.

It made more sense to me (when I was trying to figure all this out) when I looked at the flash as piggybacking the cameras metering system. Flash has nothing to do with cameras metering system - evaluative, partial, center weighted, spot, etc but uses it for it's own purposes.

Like gonzogolf stated the flash uses Evaluative or Average which you can only change via the cameras flash menus (if your camera has that feature) and uses it only for flash, not the ambient light your camera is exposing for. I like stvas's explanation about what the flash's evaluative and average settings do. Gonna have to add that one.

Like apersson850 said the only way to get spot metering for you flash is using FEC. I don't use that myself but read that many photogs meter off the skin and compensate using FEC.I tried it but never really got into it.

So you are definitely on the right track. Flash is much more interesting and enjoyable once this starts to click for you. A great feeling when your control it rather than the other way around.