I don't know what happened with my Sigma lens. Basically when I mount it on my camera everything is dark and auto focus cannot focus. It's like not enough light is coming though.

When I put other lenses on, everything is OK.

  • 3
    \$\begingroup\$ Can you provide more information? What do you mean by everything is dark? Is it completely black? Can you see through the lens when it's not attached? Is the aperture blades stuck closed? What camera are you using? And so on? Otherwise it will be next to impossible to help you. \$\endgroup\$
    – Hugo
    Jul 31, 2015 at 9:28
  • 1
    \$\begingroup\$ Have you removed the lens cap? \$\endgroup\$
    – Michael C
    Jul 31, 2015 at 22:58
  • \$\begingroup\$ Thanks a lot for your help, yes I removed the lens cap. it did not help. \$\endgroup\$
    – Slava
    Aug 1, 2015 at 10:36
  • \$\begingroup\$ What conditions are you shooting under? Are you shooting indoors or at night (i.e,. there really is not enough light?) \$\endgroup\$
    – inkista
    Jan 19, 2017 at 19:25

2 Answers 2


It sounds to me like the aperture control in the lens has failed and it will need to be serviced.

All Auto Focus camera lenses are wide open until you actually take the photo. Look though the front or rear of the lens, and it should be completely open. If you can see the hexagon type shape of the aperture blades, it means they are not working properly. You will not be able to auto focus and the viewfinder will be very dark.

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  • \$\begingroup\$ Thanks for your help Mike, seems to me this is a problem. I tried to change ISO value on a camera, but when I push the button to take a picture, on a write corner "32" is blinking (the shutter speed) - it means underexposure, but I can do anything with this - aperture on a lens is not responding. \$\endgroup\$
    – Slava
    Aug 1, 2015 at 10:41

Seems that your ISO value in the camera is set to some fixed low value.

Set ISO to "Auto" or, if you prefer to work with a fixed ISO setting, set it to some high value, e.g. 6400 and then experiment- successively set it to lower value.

  • \$\begingroup\$ Why would the problem be occurring only with the 18-250 lens? As the OP notes, other lenses are fine. \$\endgroup\$
    – Philip Kendall
    Jul 31, 2015 at 13:39
  • \$\begingroup\$ None of that would explain why the pictures are dark. \$\endgroup\$
    – Philip Kendall
    Jul 31, 2015 at 13:49
  • \$\begingroup\$ yeah, apparently SE user Mike Sowsun provided a better, more explanatory answer. - User Slava can still try to set ISO higher to check if the lens/camera combination still can yield properly exposed pictures, (which will be noisy, though) \$\endgroup\$
    – knb
    Jul 31, 2015 at 14:01
  • \$\begingroup\$ Thanks Philip, I think Mike is right - the aperture on the lens is not working. \$\endgroup\$
    – Slava
    Aug 1, 2015 at 10:45

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