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I shoot tyipically with my Pentax set to manual mode with the exception of auto focus as my older eyeballs are fading fast. While shooting a friends canon (xti rebel) I found that it has a tendency to go to a faster f stop such as 3 or rather than drop shutter speed, I believe my pentax is like this. are all cameras like this and why would that be? to change this would you just go to a self program or user mode?
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Re: JUST ANOTHER HAZY MORNING......OR WAS IT?
Sat, July 5, 2008 - 9:10 PMKurt,
What the camera does will depend on what mode you are in. Normally, I shoot in M (Manual) mode, apparently just like you. I tell the camera where to set Av (aperture) and Tv (shutter speed), both. The only variance I might have from your description is a feature in the Canon EOS system called Selective Auto-Focus, where you tell the camera what to focus on, using an illuminated designator in the viewfinder overlay screen.
On Canon EOS DSLRs, there are other modes aside from M, and they are located in the "Creative Zone" on the command dial: Av, Tv, and P, among them.
What you are describing sounds a lot like Tv Mode, or shutter-priority mode. In this mode, the shutter speed is fixed to whatever you set it to, and depending on metering, the camera automatically opens up the lens (or closes it) to provide correct exposure. Hence, Av, or aperture, is automatically adjusted in Tv Mode.
The inverse is also possible. If you wanted the shutter speed to vary (and were OK with possible concomitant blur, if it's dark), but the aperture to stay fixed (for a specific depth of field that you wanted in your shot), that would be done in Av Mode, or aperture priority mode.
Most SLRs, including DSLRs, have these modes. P is the Program shift line, where for a given Av/Tv combination, you can move up or down a line that locks the EV (Exposure Value) to be constant.
Hope this helps you grok your experience with the Rebel XTi.
Blessings and Light,
Michael -
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Re: JUST ANOTHER HAZY MORNING......OR WAS IT?
Sun, July 6, 2008 - 8:26 PMIt was not Tv or Av mode as I am discovering the benefits of both. The camera was in total auto mode, it seemed to want to go to a low aperture. I love to shoot with the highest aperture I can to get the best depth of field for scenic shots and the such. I have not ahad a chance to get to a race track yet to shoot high speed stuff.
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Re: JUST ANOTHER HAZY MORNING......OR WAS IT?
Fri, July 11, 2008 - 5:39 AMWhen in Auto mode on Canon cameras, the camera uses logic to check if the resulting shutter speed might give you blur due to being hand-held. If it "thinks" there is a chance of this, it will change the Aperture value first, then ISO (only on some cameras), and finally Shutter speed to give you the correct exposure.
They figure the loss DOF is a lesser trade-off than loss of sharpness due to blur caused by hand holding.
I hope that helps!
