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  Previous versions of BrianO's message #11286513 « Lens not auto focusing; repair or recalibrate »

  

BrianO
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Re: Lens not auto focusing; repair or recalibrate


kkennardis wrote: Not sure, when I take it off the camera the focus is past infinity both times. I even tried again, and i manualy turned the focus ring to focus much closer, then it goes back and forth then utltimately ends up past infinity. Is that what you mean?

Nope. The aperture is the hole in the iris through which light travels. When you change from -- for example -- f/4 to f/5.6 the aperture gets smaller.

AF requires a fair amount of light to work, and so modern cameras are designed so that the aperture is at its widest during focusing and then closes down to the shooting aperture when the shutter is released.

If the aperture is stuck in a small position there won't be enough light reaching the AF sensor, so it will "hunt," trying but unable to lock focus.

One way to tell if your aperture is stopped down is to set the camera for a smaller-than-maximum aperture (smaller than f/3.5 on your camera) and -- while looking through the viewfinder -- press the Depth of Field preview button. You should see the image in the VF get a little darker. If not, it may be stuck at a smaller aperture than the one you set. Kepp repeating the experiment at progressively smaller apertures until (if) you can see a change in the VF to know where it's sticking.



Jan 21, 2013 at 02:51 AM



  Previous versions of BrianO's message #11286513 « Lens not auto focusing; repair or recalibrate »