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 p.1 #6 · Smallest Auto-thyristor flash... | |
Have you ever used an auto-thyristor flash? I suspect not because of your list of requirements including EV compensation. The way they work is the dial on the flash is set for the f/stop the camera is set on. If the exposure at those settings winds up not being correct you then need to either change camera aperture or the flash power setting. There is no "EV adjustment" on the flash and typically the auto settings are one f/stop apart. So to find tune exposure -- which is just as necessary with auto as any other mode based on scene reflectance - you wind up changing the aperture which affects DOF, an important creative variable.
Having used Auto thyristor Vivitars for 30+ years before switching to Canon I can venture to say that Canon does a far better job once one grasps how the exposure system works. The metering is done by the camera body and I suspect the big part of the problem in your case is the 1D you are using which utilizes the first-generation Canon flash metering called "ETTL" which is based on active AF points. Your other two cameras are ETTL-II bodies which use the evaluate zone method for flash and ambient exposure.
The trick with ETTL-II to the extent there is one is to first adjust shutter speed and aperture so an ambient only exposure keeps everything below clipping. The ambient level is the baseline the evaluative flash metering measures against and it its blown the camera metering will tell the flash to output less power than necessary. When the ambient is correctly exposed (which may take as much as - 2 EC in Av mode) the ETTL-II flash does a very good job of matching a shaded foreground to a sunlit background.
Even more basic technique-wise is realizing fill flash only works when shooting into the shadow side. The point of the exercise is to reduce the contrast of the scene (which may 12 or more stops in backlight) to fit the 7 stop range of detail the sensor can record. The flash can only reduce a scene range if it does not overlap the sunlit highlights. For example, you can't expect flash to fill the dark eye sockets of a sun lit face because the flash also overlaps the sunlit parts of the face and blows the highlights as it tries to raise the shadows. Raising shutter speed will reduce the ambient in both highlights and shadows and simply trades flat sunlight for flat flat. But in a backlight situation when the shutter is set to keep the sunlit hair and clothing under clipping the flash can lift the shadows, effectively reducing the contrast range of the foreground subject, without overlapping the sunlit highlights.
The key to success with flash outdoors is knowing how best to use the ambient light and compose the scene for flash, shooting into the shadows of the ambient light so the flash can work independently of it to lower the contrast range of the scene. Once that it grasped the type of flash used makes very little difference because regardless of what controls flash output the physics remains the same: flash can't do its job to reduce contrast unless it operates independently and does not overlap the sunlit highlights.
All things considered you'd have better consistent control of flash power with a Canon flash in M mode which allows power level adjustment in 1/3 stop increments and takes metering out of the equation. Manual is really no more difficult than ETTL and the workflow is the same: take a shot (which is usually correct about 1/2 the time), then adjust power based on camera playback (use the over exposure warning). The only difference is flash power is controlled directly with the power setting rather that with the FEC dial in ETTL. Both have the same net effect of changing flash duration which changes exposure and once set the manual will be consistent shot-to-shot while ETTL will react to changes in background reflectance of the scene and will be affected by focus / recompose.
Chuck
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