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Old Sep 6, 2005, 6:30 PM   #1
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I'm new to this kind of lenses, and I'll be using a Canon S2 IS camera, and I'm willing to buy some wide angle lenses and teleconverters. Now my question is quite simple; I've seen the camera calculates shutter speed and aperture automatically, or you can set up shutter or aperture priority. In all three cases, values are calculated based on the actual focal length you're using, and that gives you the proper calculation to get a good picture.

Now if I add a teleconverter or macro lense, I'm alterating focal lenght, and thus the aperture capabilities of my lense, without letting the camera know about it, so pictures could get under or overexposed easily, am I right?

Is there any workaround to compensate for this without using manual settings?

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Old Sep 6, 2005, 9:55 PM   #2
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schmiedel wrote:
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Now if I add a teleconverter or macro lense, I'm alterating focal lenght, and thus the aperture capabilities of my lense, without letting the camera know about it, so pictures could get under or overexposed easily, am I right?
I could be wrong, but no IMO. The exposure is calculated with what the CCD sees at the moment, thus you always got the perfect exposure. what can affect is the exposure program "shifting" (or what ever name it has). The camera is then enable to give you the best combinationfor the focal lenght used , for example priorizing high speed when in tele or priorize small aperture at wide angle. But this is not that important since the camera is probably at near full tele with a tele add on, and same with a wide angle add on.

Another possible miscalculation is flash exposure with distance integration. The flash program may have false data to give the best flash exposure.
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Old Sep 7, 2005, 8:23 AM   #3
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Pretty sure that any exposure variation due to add-on lens is dependent on the camera.

Mine, for example, seems to work fine, even though what the manual calls the exposure sensor is external, next to the camera lens and largely blocked by auxiliary lenses.

The presence of a spot metering option, however, suggests that there is through-the-lens exposure adjustment, and spot metering definitely works with both my wide-angle and my cobbled-up connection to a spotting scope for tele.
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Old Sep 7, 2005, 12:28 PM   #4
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DGehman wrote:
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... what the manual calls the exposure sensor is external, next to the camera lens and largely blocked by auxiliary lenses.
DGehman, could it be the flash sensor ? (my cp950 also has an external flash sensor, although the flash is electrically controled via ttl protocol)
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