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Old Mar 9, 2006, 12:44 PM   #1
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Can someone explain the effect that center-weighted average metering has on exposure when I am shooting with a digital rebel 300d using the manual mode for shutter speed and aperture? I have noticed that when I shoot in continuous shooting mode and get consecutive pictures a fraction of a second apart, the photos look markedly different regarding exposure. One looks under exposed and the very next one looks over exposed even though neither the manual shutter speed nor the aperture settings were changed and of course their histograms are drastically different as well. Since the consecutive shots are taken so close together in time, the scene is essentially unchanged.
I expected that the metering indication in manual mode was more of an advisory to which you could react if you wanted to get a "properly" exposed shot. If the metering indicated an underexposed condition, for example, and you didn't make any change in shutter speed or aperture then the shot would be under exposed. What's going on here?
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Old Mar 9, 2006, 1:35 PM   #2
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I have not had this experience. Are you sure you don't have exposure bracketing set by accident? It sounds like you do.
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Old Mar 9, 2006, 1:58 PM   #3
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I don't think AEB was set. If it was it was an accident. If it had been set accidently wouldn't that be indicated in the file info on the Canon File View utility for the shots affected?
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Old Mar 9, 2006, 3:07 PM   #4
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Have you tried taking pictures of some stationary object in a sequence while in manual mode? the exposure shoudn't change as you say but then again the original 300D was made quite dumb by canon as to what it will do based on what mode it was.
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Old Mar 9, 2006, 3:22 PM   #5
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Bobbz
Yes, today I shot a few bursts of a stationary object and didn't see any change in the apparent sxposure.

The problem happened last night on action shots taken at a softball game under the lights (1/500, using 85mm f1.8 prime lens at ISO 1600).
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Old Mar 9, 2006, 3:25 PM   #6
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It shouldn't be changing unless the lighting is changing (and the human eye is not going to notice it the way a camera's lens would).

Are you shooting under flourescent lighting? If so, the frequency of the lighting comes into play, depending on your shutter speeds and can cause exposure problems. You see this referred to as the "flicker factor" from time to time.

The human eye sees the light as steady, whereas the camera can see it as flickering.

Solution: Slower shutter speeds to help even it out.

P.S. --

As for your softball game (depending on the type of lighting), I'd suspect that there is more difference in lighting than you think during the burst of images being taken.

But, I could be wrong, and perhaps some Canon owners may be more familiar with any kind of camera issue that could be causing it.

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Old Mar 9, 2006, 4:23 PM   #7
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Thanks for the replies. My assumption has been that the exposure should not change when I am in the manual mode. That is true--right? What I am seeing is really weird. I had not noticed it before getting a new 85mm f1.8 lens a few days ago. I shoot a lot at night games and prior to acwquiring the new lens was forced to use the flash. As a result I didn't using the continuous shooting mode. With the f1.8 lens I can shoot at high shutter speeds and in continuous mode. I wonder if the weird effect is somehow related to the new lens (it is a Canon refurbished lens).
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Old Mar 9, 2006, 4:57 PM   #8
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coachjerry

What about white balance?
I bet you still have it on automatic correct! :-)

-> The exposure may not change, but the pictures do look different from one to the next...

(I also recalled with the Rebel in some modes it has auto ISO as well, so make sure they are all fixed)
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Old Mar 9, 2006, 5:00 PM   #9
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Hi NHL
Auto White balance was on-if that's what you are asking.
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Old Mar 9, 2006, 5:05 PM   #10
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coachjerry wrote:
Quote:
Auto White balance was on-if that's what you are asking.
Correct - change it to tungsten if that's what you are shooting @...

But your problem may be different:
-> Be careful with gym arc light since they cycle on/off with the AC duty cycle and if you are (i.e. shutter speed) at same frequency you could be catching the ligths at the wrong time!
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