I have a most vexing problem.

I have a Nikon d5100 (roughly a year old) which up until two days ago handled exposure and metering just fine. However, at night, in a well lit room (florescent bulbs) in which I NEVER had problems capturing images at reasonable shutter speeds, apertures and ISOs (< 400), here's what's happening now:

  1. In Manual, even at low shutter speeds (1/90 and lower) and relatively open apertures (3.5) - ISO 640 and less - my pictures are almost completely black. Pointing the camera at a bright lightbulb just barely captures the light with heavy shadows all around it.
  2. Exposure compensation no longer has ANY effect on the exposure
  3. Shooting in Aperture Priority mode at f/3.5 at anything lower than ISO 1000 reduces my shutter speeds to 1/2 or lower to compensate.

Yes, I know. ISO. Keep in mind, the room is quite brightly lit and I never had this issue prior to last night. That being said, the only way I can capture a reasonably exposed picture here is at ISOs 6400 and above. But even a picture at 1/125, f/5.6, ISO 6400 (manual) is still ridiculously dark.

I have taken the following step to troubleshoot, to no avail:

  • Turned exposure compensation up to the max +5.0 - no effect
  • Turned shutter speeds down to 1/40 and below - extremely limited effect
  • Turned ISO up to 6400 and beyond - limited effect
  • Update the camera's firmware (1.01 > 1.02) - no effect
  • Reset the camera using the buttons with the two green dots - no effect, multiple tries
  • Messed with the metering modes - no effect
  • Turned it off and on again - no effect
  • Stared pointedly at the camera - camera didn't even flinch

I am at an absolute loss here and I really, truly, need help.


ISO 100, f/3.8, 1/3
ISO 100, f/3.8, 1/3

ISO 100, f/3.8, 1/90 ISO 100, f/3.8, 1/90

ISO 1000, f/3.8, 1/90 ISO 1000, f/3.8, 1/90

  • \$\begingroup\$ Are you using flash? \$\endgroup\$
    – inkista
    Jan 30, 2015 at 4:43
  • \$\begingroup\$ No flash. Never needed it in this setting before. \$\endgroup\$ Jan 30, 2015 at 4:46
  • \$\begingroup\$ I would try reseating the lens, or using another one. Then vary aperture (in Manual) from 3.5 to f/11 or 16 and make sure the images get darker. If not, maybe everything is taking at the minimum aperture for some reason. \$\endgroup\$
    – MikeW
    Jan 30, 2015 at 4:57
  • \$\begingroup\$ You could look through the lens as well, to check the aperture and the approx. shutter speed (set to 0.5 second and make sure shutter is actually open that amount of time, and mirror locking up completely) \$\endgroup\$
    – MikeW
    Jan 30, 2015 at 4:58
  • \$\begingroup\$ Is this with more than one lens? If you have more than one, try several. | If you have only one and regardless, unseat lens and reseat several times. Lens to body contact issues can cause VERY strange problems. | If still no go the 99% chance it's dead. | Reset everything (as you have done). | On averagely lit say manually set to 100 ISO, f8,1/125th s. What do you get? \$\endgroup\$ Jan 30, 2015 at 5:21

3 Answers 3


it is with shame in my eyes and regret in my heart that I answer my own question:

All my problems stemmed from a single setting change. I looked back at the metadata of pictures I had taken in the same location/circumstances and was quite surprised to see most of them in the region ISO 6400. Now, I rarely set my ISO that high so imagine my confusion. Upon the advice of a friend, I dug through the menus for a bit and found a setting called "ISO sensitivity settings" and there I discovered that "Auto ISO Sensitivity Control" by default had been on. In summary, for the year that I've been shooting with this camera, auto ISO has been enabled, so even if I had set ISO 100 from the settings screen, this buried menu option would override it - hence the large number of low light pics in my library with very high ISO.

Despite my own inexperience being at fault, I truly appreciate all the excellent advice you fine people have given me. I will leave "auto ISO" to rot in the dark all by its lonesome for now, and learn to use my camera properly

  • \$\begingroup\$ Don't be down on auto ISO. It's the right tool for many situations, just as letting the camera choose the shutter speed and/or aperture are right in many situations. \$\endgroup\$
    – Philip Kendall
    Feb 2, 2015 at 19:41
  • \$\begingroup\$ I agree @Phillips Kendall, just making sure that what it does, I can do on my own - understand the process so to speak. Then I can let it do it's thing again :) \$\endgroup\$ Feb 2, 2015 at 19:50

I have seen problems like this occur when the contacts between the lens and camera are either dirty, not lined up, or breaking communication for some other reason.

Do you have another lens you can try?


Remove the lens and clean the contacts - on the lens and the body - which I see you haven't tried. Remove the battery and reinsert. I faced the same problem once and these worked.


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