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Thread: DSLR set to M and using external flash produces correct exposure?

  1. #1

    Default DSLR set to M and using external flash produces correct exposure?

    Hi,
    I was experimenting with my D70 and external Metz 54 MZ-4 flash, which doesn't support iTTL and the exposure data does not be sync automatically, so I used 'A' mode on the flash to do test shots.

    I found out that as long as my Aperture and ISO settings are set the same on the camera and the flash (e.g. f8, ISO 200), I can choose whatever shutter on the camera and still get correct exposure (e.g. 1/500, or 1/25).

    Being a newbie in flash photography who always uses TTL or Auto on both camera and flash, I just want to ask whether this is the correct expectation? Which is to say, whatever shutter I choose while aperture is fixed, the flash will automatically fire and expose the frame correctly?

  2. #2
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    depends. if your choice of aperture and shutter speeds result in underexposure of ambient lighting, the flash will be the main source of illumination and when aperture and ISO are set the same, you'll get probably exposed flash pics.

    if your choice of aperture and shutter speeds result in overexposure of ambient lighting, you'll get overexposed pics (even if the flash is turned off).

    For the 2 shutter speeds you stated, the diff between the two pics would be the amount of ambient lighting captured. The 1/25s pic would have more of the ambience preserved vs the 1/500s pic.

  3. #3

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    Yes you are right that the slower shutter speed retains ambient light.

    So based on your statement on the first para, as long as my cam setting is underexposed, the flash (when set with correct ISO and Aperture as the cam) will compensate to capture correct exposure (limited by the maximum power of the flash, that I understand).

    Wonderful!

  4. #4
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    yup, that's how it's supposed to work.

    you could apply flash exposure compensation too by varying the aperture on the camera to be different from that set on the fash. if you set the flash to f4 and the camera to f2.8, you're applying +1EV flash exposure compensation. if you set the flash to f4 and the camera to f5.6, you're applying -1EV flash exposure compensation.

  5. #5

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    Quote Originally Posted by mpenza
    yup, that's how it's supposed to work.

    you could apply flash exposure compensation too by varying the aperture on the camera to be different from that set on the fash. if you set the flash to f4 and the camera to f2.8, you're applying +1EV flash exposure compensation. if you set the flash to f4 and the camera to f5.6, you're applying -1EV flash exposure compensation.
    Yes, that I am aware of. My flash doesn't support iTTL with D70 and doesn't communicate the ISO and aperture, so I was thinking of using manual mode to fix the values as a workaround, thereby no need to keep changing settings on both equipment. I am actively seeking either a new SCA adaptor (for Auto support) or get an upgraded 'i' version (for iTTL support).

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