Why does my Canon 60D choose a much slower shutter speed in Av than in Auto or P mode?
Asked 2/14/2013
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2 answers
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On my Canon 60D, I compared the same scene in different exposure modes. In Auto, the camera chose about 1/60 sec at f/4 and ISO 400. When I switched to Av mode and set f/4 and ISO 400 manually for the same shot, the camera chose about 1/6 sec instead. I also noticed the image looked a little different, possibly due to white balance or another automatic setting.
I repeated the test comparing P mode and Av mode and still saw different results. Why would the shutter speed change so much if the aperture, ISO, and scene are the same?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
3
It would be easier to compare Program versus Aperture priority because Auto ignores a lot of other settings, most importantly Exposure-Compensation and choice of metering patterns. The ignored settings depends on the camera and I do not have a 60D on hand to check.
Had you changed any of these settings on your camera you would have a large discrepancy. The other thing is that flash works differently in Auto on plenty of cameras. This may enforce a minimal shutter-speed like 1/60s and ask the flash to fire. While in A mode, the flash wont fire unless the right Flash-mode is set and therefore a lower shutter-speed is required.
To find out what is the case in your setup, do the same comparison between P and A. If those coincide, then you have to try different settings to see which one is ignored in Auto mode.
Originally by user1620. Source · Licensed CC BY-SA 4.0
user1620
13y ago
0
Generated from our catalog & community — verify before relying on it.
Yes, this can happen because Auto, P, and Av do not necessarily use the same internal rules.
On the 60D, full Auto can ignore or override settings such as exposure compensation, metering choices, and flash behavior. Auto mode may also enforce a safer handheld shutter speed like 1/60 sec, especially if it expects flash use or is prioritizing blur avoidance.
In Av mode, the camera’s job is simply to meter the scene at your chosen aperture and ISO, so if it thinks the scene needs more light, it may select a much slower shutter speed such as 1/6 sec.
Program mode is a better comparison than full Auto, because Auto changes more camera behavior behind the scenes. If P and Av still differ, check for settings like exposure compensation, metering mode, or flash-related behavior. Those differences can change the meter reading even when aperture and ISO are the same.
So the short answer is: the exposure modes are not identical, and full Auto especially may apply extra assumptions that Av does not.
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