I have been using a Canon 60D for five years and recently, only when I am using my Sigma 24-70mm lens, it does not let me take pictures. When I look into the viewfinder, it is so dark (I assume that the lens is not capturing light). And the camera either does not respond (i.e., when I press the shutter button to take a picture, it does not respond) or even if it does, the pictures turns out to be very dark. This behaviour is so abnormal and totally random. One minute it is working fine and the next moment it goes nuts. I have tried re-mounting my lens but it still does not make a difference.

I also have a 50 mm lens but my camera works fine when I use that.

Can somebody please help me understand what's the issue and how to fix it? I am a total noob when it comes to photography and this issue is really making me anxious.

  • \$\begingroup\$ Does the lens work on other camera bodies? \$\endgroup\$
    – Caleb
    Dec 25, 2018 at 5:44

1 Answer 1


It sounds like your Sigma 24-70 has sticking aperture blades. If it happens only intermittently, you can try and free them up. Select a small aperture like f/22 and use your depth of field preview button to open and close the aperture blades rapidly.

I have an old Canon 28-70mm f/3.5-4.5 from 1989 that used to do this. I didn’t really use this lens much, but it bothered me that the blades were sticking. So, once a week or so I would play around with the DOF preview button and it slowly got better over time. It rarely sticks now.

Depth of Field Preview Button Explained


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