Problem with Av mode in Canon 500D


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May 13, 2009
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#1
Hi,

I am using Canon 500D.

Not sure if anyone of yours experience this before: When shooting in Av mode, especially in slightly low light condition, the camera always tend to use slow shutter speed, like 0.5", or 1/8, even i using higher ISO like 1600, is it something wrong with my camera?:think:
 

tehzeh

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Aug 7, 2009
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#2
Aiyo.. no lah.. Because it's aperture priority.. so you can only adjust ur aperture and the exposure comp.. (If I am not wrong..) and ISO.. so the shutter speed will be adjusted by the camera itself to coordinate with your aperture, to have a suitable exposure. :)

Correct me if I am wrong.. tyvm. :)
 

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limwhow

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Jun 9, 2009
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#3
May I ask, what aperture did you set while in Av mode?
And importantly, what kind of lighting did you have? Indoor with tungsten or fluorescent light?
 

Dream Merchant

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Jan 11, 2007
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#4
If you use the same set of parameters, same exact framing, focal length, ISO, aperture, what do the readings on other modes say? Or just go to manual and check. Make sure that ALL safety shifts, AUTO ISO, exposure compensation are switched off or set to 'O'.
 

Burnings

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Dec 10, 2009
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#5
I am also using a 500D and since I am a newbie I need to experiment with the different settings to get things right. How I did it initially is to switch to auto mode and fixed the focal length first and see what is the settings and then I will switch back to other modes and adjust from there as sometimes we wanted more bokeh effects, darker BG, etc... :)
 

#6
In Av mode (which is the aperture priority mode), you can control the aperture mode but not the shutter speed.
The shutter speed is defined by the camera to capture images with the correct exposure. ;)
 

two200

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#7
I am also using a 500D and since I am a newbie I need to experiment with the different settings to get things right. How I did it initially is to switch to auto mode and fixed the focal length first and see what is the settings and then I will switch back to other modes and adjust from there as sometimes we wanted more bokeh effects, darker BG, etc... :)
In auto mode, the camera sets the ISO, aperture, shutter speed. In Av mode, you set the aperture and ISO. This leaves the camera to adjust the shutter speed only.
 

Ah Pao

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Nov 7, 2003
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#8
In both Av and Tv modes (A and S in Nikon), the camera will meter the ambient ("background") light even with the flash switched on. So in Av/Tv mode and low light, your flash will act as a fill-in for your subject. The camera will try to expose for the background instead of just the subject alone. That is why the camera selects a low shutter speed to capture the background light.

If you don't get what I mean, try taking a picture of someone against a dark background at night, with flash, using your Auto/P and Av mode. You will see the difference between the two shots.
 

ZerocoolAstra

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Mar 13, 2008
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#9
In both Av and Tv modes (A and S in Nikon), the camera will meter the ambient ("background") light even with the flash switched on. So in Av/Tv mode and low light, your flash will act as a fill-in for your subject. The camera will try to expose for the background instead of just the subject alone. That is why the camera selects a low shutter speed to capture the background light.

If you don't get what I mean, try taking a picture of someone against a dark background at night, with flash, using your Auto/P and Av mode. You will see the difference between the two shots.
That's not exactly correct though, coz it depends on the type of metering you use. When I use spot metering on the subject, the background is ignored.
But you are right that in A mode (on a Nikon), the camera seems to prefer a lower shutter speed, and using the flash/speedlight as fill-light.
 

Octarine

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#10
That's not exactly correct though, coz it depends on the type of metering you use. When I use spot metering on the subject, the background is ignored.
But you are right that in A mode (on a Nikon), the camera seems to prefer a lower shutter speed, and using the flash/speedlight as fill-light.
That's the standard that Canon has defined. Back to the initial question.
Low light conditions will result in slow(er) shutter speed, no matter what you set in ISO. That's pretty normal because if there is not enough light then the camera has to open the shutter for a longer time to "collect" light in order to obtian a proper exposure for the image. ISO1600 is just 4 stops more than ISO100, that's not much. If the difference between daylight exposure and your scene is more than that then it's just normal that the shutter speed will drop to compensate this.
 

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