Metering emang aga beda antara make flash n ga,
Kl make flah, metering jg beda antar mode P, Av, M di canon, kl nikon gw kurang tau
Gw ada "bahan bacaan mengenai metering flash tp dlm inggris
Program (P) mode flash.
The overriding principle of Program (P) mode in flash photography is that the camera tries to set a high shutter speed so that you can hold your camera by hand and not rely on a tripod. If that means the background is dark, so be it.
Program mode operates in one of two modes, depending on the ambient (existing) light levels.
1) If ambient light levels are fairly bright (above 13 EV) then P mode assumes you want to fill-flash your foreground subject. It meters for ambient light and uses flash, usually at a low-power setting, to fill in the foreground.
2) If ambient light levels are not bright (below 10 EV) then P mode assumes that you want to illuminate the foreground subject with the flash. It sets a shutter speed between 1/60 sec and the fastest X-sync speed (see above) your camera can attain. The aperture is determined by the camera’s built-in program.
Because the camera tries to keep the shutter speed at a reasonable speed for handholding the camera you will end up with dark or black backgrounds if you take a flash photo in P mode when ambient light levels are not bright.
On most if not all EOS cameras, P mode is not shiftable when flash (internal or shoe-mounted Speedlite) is used. Note also that DEP mode cannot work correctly with flash - its metering settings basically revert to P mode if you try it.
Av (aperture priority) mode flash.
Av mode lets you set the depth of field by specifying the lens aperture. The camera then chooses a shutter speed ranging from 30 seconds to the camera’s X-sync speed, in order to expose the background correctly. If that means the shutter speed is some really low value so that you need to use a tripod to avoid camera-shake blur, so be it. In dark conditions, therefore, Av mode works in slow sync mode.
Flash duration (flash output) is determined by the flash metering system. Like Tv mode the camera always works in fill flash mode when in Av mode.
There is one exception to this. A number of EOS cameras have a custom function you can set to ensure that the shutter speed in Av mode when using flash is locked to the X-sync speed. The EOS 10/10s and Elan II/EOS 50, for example, have such a custom function, which lets your camera behave more like P mode when in Av mode. However this custom function will only lock the camera to X-sync in Av mode and will not choose a shutter speed from 1/60 sec to X-sync, the way P mode does.
As always, the camera will prevent you from exceeding its built in X-sync speed unless FP mode is available to you and engaged. If the shutter speed value of 30" flashes in the viewfinder then there isn’t enough light to expose the background correctly and you’ll need a larger aperture or faster film. If the camera’s X-sync flashes in the viewfinder then you’ll need to decrease the lens aperture, engage FP mode if it’s available or use slower film.
Manual (M) exposure mode flash.
In manual exposure mode you specify both the aperture and shutter speed, and your exposure settings will determine how the background (ambient lighting) is exposed. The subject, however, can still be illuminated by the automatic flash metering system since the flash can automatically calculate flash output levels for you. This is a marked contrast to the olden days, when photographers would carry around little flash exposure tables with them in order to work out manual flash settings.













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