G1 Flash Photograph 101

Started May 21, 2001 | Discussions thread
Shaam Shilome Regular Member • Posts: 150
Re: G1 Flash Photograph 101

I have a quick but may sound like a dumb question.....Is there any other way to tell if a G1 is overexposed or underexposed other than just looking at the picture?....How does one really know for sure what the real sweet spot of a perfectly exposed picture?...whether it be a portrait, a landscape...ect.?

Other than just visualizing it ...what other ways can I determine whether or not an image is correctly exposed....I'm not just reffering to Flash shots but mainly outdoor shots.....I'm sorry if this sounds like a dumb question but i am finally venturing out of full auto mode on my G1 and want to try manual mode.

thanks!

euthon wrote:

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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