G1 Flash Photograph 101

Started May 21, 2001 | Discussions thread
euthon New Member • Posts: 21
Re: G1 Flash Photograph 101

When you put ANY standard non-Canon strobe on it
this happens: the flash will fire shortly BEFORE the aperture
stabilizes at the intended aperture. For example, if you set the
camera to f5.6 at 1/125 the actual aperture goes through a very
brief transition phase before the aperture actually stabilizes at
f5.6. During this transition phase the aperture can be any value,
be it f2.0 or whatever. What happens is that the G1 will fire your
non-Canon flash during this transition phase in stead of waiting
until the aperture reaches the intended value. Yet, somehow it
manages to do the right thing whenever an EX flash is mounted on.
Selective wrong doing!

My experience is different from yours. So, either not all G1's exhibit this behavior or not all manual flashes are equal.

I just run a quick and dirty test and here are the results:

Equipment:

  • Flash: Spectrum 370T Auto flash in manual mode, bounced off the ceilling to prevent gross overexposure, plugged into the hot shoe.

  • Camera: Canon Powershot G1, updated firmware, zoom set at its longest, 1/125 shutter speed, manual focus, on a tripod, ISO 50, RAW mode.

  • Target: 8x10" gray card, about 4 feet from the camera.

I shot the card at f/2.8, 4.0, 5.6, 8.0 and exported images into Photoshop. Below are averaged RGB values for each shot:

f/2.8 -- R: 199, G: 190, B: 172
f/4.0 -- R: 125, G: 117, B: 103
f/5.6 -- R: 111, G: 106, B: 92
f/8.0 -- R: 23, G: 22, B: 20

White balance was set to "flash".

I repeated the test several times and the results were pretty consistent.

I can definitely see the problem you describe around f/4 - f/5.6, but it's not nearly as bad as in your case. The problem can be solved easily and cheaply: slave your manual flashes optically.

euthon

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