Im having problems when im using the auto iso mode in my canon rebel t3i whith the optical viewfinder but not when i use the lcd monitor. whe i use the optical viewfinder the exposition and iso change and the picture take so long to take. but not when i change to the lcd screen to take the picture.

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    Besides how you view the image composition, what other settings are different when using Live-view compared to using the optical viewfinder? Live View meters and focuses differently, and within each of those systems settings may not be similarly selected.
    – Michael C
    Jul 9, 2013 at 10:58

1 Answer 1


The question would be why is it taking a long time when using the optical viewfinder. Different metering is used for optical (using the metering sensor) since the mirror is down vs direct measurement using the CMOS sensor when the mirror is up (LiveView). Something may be wrong with your metering sensor. First I'd check to make sure your metering settings are on the defaults, if they are and it is still causing problems, I'd try another lens if you have one, if the problem still persists, it might be worth having a camera shop or a Canon service center take a look at it.

  • What does E-TTL have to do with this question? He doesn't even mention using flash and the long exposure tag would lead one to believe he is not using any kind of flash. E-TTL uses a pre-flash to determine proper exposure, and doesn't come into play when all of the light is ambient.
    – Michael C
    Jul 9, 2013 at 11:01
  • I was thinking that E-TTL applied to any metering that was through the lens using the metering sensor (since it is part of the E-TTL system, even if it isn't using the external flash portion). I have removed references to E-TTL to avoid confusion though since I couldn't find anything firmly defining if E-TTL is only a correct term when dealing with flash.
    – AJ Henderson
    Jul 9, 2013 at 14:23

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