May 27, 2018, 06:01:44 PM

Author Topic: IS mandatory? 70-200 f/4 IS vs. f/2.8 Non-IS  (Read 24579 times)

jcollett

  • EOS Rebel SL2
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Re: IS mandatory? 70-200 f/4 IS vs. f/2.8 Non-IS
« Reply #30 on: April 17, 2013, 12:48:14 PM »
Thanks Paul13walnut! I always wondered about that. I thought you had to shoot at 2.8 all the time.



No.

From the mid sixties most SLR cameras have had full aperture TTL metering.

That is the iris stops down to shooting aperture at exposure, it remains open before exposure to keep the viewfinder bright for focusing.  Meter coupling, and these days electronic interfaces, tell the meter how much to compensate the reading for.

So if you have an f2.8 or faster lens, the af is performed at f2.8 or faster, even if you shoot at f8 all the time.

If you want to see what your sensor will see when the shutter is activated, use the DOF preview button on your camera.  For many Canons, it is on the lower side of the lens mount away from the shutter button.  On the 5D mark iii, it was moved to the shutter side of the mount.  Regardless, find it on your body and before you take the  picture, press and hold that DOF preview button.  It will stop down the aperture to your set value and you can see through the viewfinder or live view the actual light amount (and Depth of Field).

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Re: IS mandatory? 70-200 f/4 IS vs. f/2.8 Non-IS
« Reply #30 on: April 17, 2013, 12:48:14 PM »