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Archive 2015 · 300 f/4L IS stuck aperture blades

  
 
Fast6
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p.1 #1 · p.1 #1 · 300 f/4L IS stuck aperture blades


Just discovered massive overexposure problems with my trusty 300 f/4L IS, and have confirmed that the aperture blades barely move from wide open (and the little bit they do move is asymmetrical).

Has anybody else had this happen, and what was the cost to fix it, and are there any non-send-it-in-for-repair options (light incense, speak occult spell, sacrifice goat, caress lens barrel)?

Hey, for the time being, it works great wide open!



Apr 16, 2015 at 11:58 AM
jcolwell
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p.1 #2 · p.1 #2 · 300 f/4L IS stuck aperture blades


It sounds like you have a problem with the aperture gizmo. You try to 'exercise' the blades for a while with frequent pushes to the DOF preview button. Worth a try. Otherwise, it sounds like a trip to the repair shop is in order.




Apr 16, 2015 at 02:24 PM
Fast6
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p.1 #3 · p.1 #3 · 300 f/4L IS stuck aperture blades


Thanks Jim. I've twiddled the DOF button a fair amount, and the extent to which the blades close each time is the same.

Maybe I'll give that button a better workout as a last resort.



Apr 16, 2015 at 03:24 PM
riokid
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p.1 #4 · p.1 #4 · 300 f/4L IS stuck aperture blades


If you have not done it yet, apply a little alcohol on a cotton swab at the gold contacts.

HTH

dan



Apr 16, 2015 at 04:03 PM
Fast6
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p.1 #5 · p.1 #5 · 300 f/4L IS stuck aperture blades


Yep, alcohol was no help. Thanks though!

Further characterization of the blade behavior leads me to believe that it's totally hosed...it will stop down to three positions, and then repeat those three as I continue through the aperture range.

Camera's set to 1/3 stops, and as I stop down from f/4, the blades do the following:
4.0, 4.5, 5.0, 5.6, 4.5, 5.0, 5.6, 4.5, 5.0, 5.6, 4.5, 5.0, 5.6, 4.5, 5.0, 5.6, 4.5, 5.0, 5.6 (at which point the camera says it's at f/32)

No bueno!



Apr 16, 2015 at 09:27 PM
Jefferson
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p.1 #6 · p.1 #6 · 300 f/4L IS stuck aperture blades


... Which body is it on ... ? Maybe try the lens on a different body or another lens on the same body ... ?

Put the body in manual mode and set aperture to f/4 ... f/11 ... etc.

Do the same with the lens on a second body ...


Jefferson ...



Apr 16, 2015 at 09:52 PM
Fast6
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p.1 #7 · p.1 #7 · 300 f/4L IS stuck aperture blades


Jefferson- thanks. All in manual mode. First noticed on 1DX. Put the 300 on a 5D3, exact same behavior. Different lenses on 1DX, normal behavior.


Apr 16, 2015 at 09:58 PM





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