I am a newbie photographer and had a question that has been plaguing me for some time now.

My NIKON D3100 camera's brightness meter (the lines that change on manual mode when one adjusts shutter speed) is clearly not working correctly. The reason I say this is because whenever I take a normal photo (manual mode) using 400 IS0 and 5.6 F-STOP, my shutter speed must be 1/10 to attain "normal" brightness, or brightness in the middle of the lines. This is unusual because 2 months ago, I was using manual mode, and taking photos at 400 ISO, 5.6 F-STOP, and 1/640 shutter speed; the brightness meter displayed "normal" brightness. Can someone provide insight into what has occurred, please? All my photos now turn out dark and I really just want to shoot like I was 2 months ago!


  • Two months ago you were using a faster shutter speed (1/640), today you need a slower shutter speed (1/10) to meter correctly but the images are underexposed (assuming identical subject and conditions)? There's meter mode (matrix, spot) that can change but the camera or lens sounds broken to me. Do you have a different lens to try? – Jasen Sep 25 '15 at 3:45
  • Have you recently disabled Auto ISO? Perhaps by doing a default settings camera reset? – Michael C Sep 25 '15 at 4:06
  • See also photo.stackexchange.com/questions/60591/… If the aperture control linkage has been bent it could be stoping down your lens when the camera thinks it is still wide open (which it always should be when metering and focusing). Normally the aperture is only stopped down the instant before the shutter opens. Even if you have selected, say, f/22 the lens should be all the way open during metering and focusing. The camera automatically compensates for the difference between the metering aperture and the shooting aperture. – Michael C Sep 25 '15 at 4:11
  • The same thing would happen if your lens aperture diaphragm is stuck stopped down. – Michael C Sep 25 '15 at 4:13
  • Can you post some example photos, ideally in different situations? It may also just be that something is broken — have you contacted Nikon service? – mattdm Sep 27 '15 at 7:47

One other point, is the camera spot metering or using some other metering? It could be that the "brightness" meter is focusing on one part of the picture than the rest or related.

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  • That's a good idea... Problems with Spot metering is always a good bet. Wish I'd thought of it. :) – WayneF Sep 25 '15 at 22:13

I suspect operator error is always much more likely than a hardware defect.

Possibly the lighting is NOT the same in both instances. You did not mention the lighting, so it seems reasonable to first of all to assume this is the problem. Any darker scene will require more exposure. Tell us how the lighting is known to be the same light level in both cases?

Possibly Auto ISO is set On, and the ISO 400 you are setting is merely the Minimum ISO, but Auto ISO can still change (with lighting). The final ISO actually used will show in the Exif data with the image. What does it say was used in both situations?

Possibly you have Exposure Compensation set to some value, which does affect what the meter will indicate. However, this would affect the brightness result that you centered.

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The answer to this is: Did the lightning conditions change? Aperture, ISO and shutter speed and the available light are in a close relationship with each one. If the light conditions change, any of those parameters that you can influence need to change.

This has, for sure, a direct influence on other aspects of your picture.

  • Increasing the shutter speed will freeze fast movements, decreasing it will blur those.
  • Increasing the aperture i.e. lower f-stop will let more light on the sensor, but will decrease the depth of field (mostly the background will get a nice blur). Decreasing the aperture will increase the DOF, but will let less light on the sensor.
  • A low ISO will need more light on the sensor, a higher ISO will get correctly exposed pictures in low light situations. But a high ISO will increase the (visual) noise of the picture.

So all is a trade-off on the effect you want to have with your pictures. If the light situation is not correct for your camera setting, you may use flash lights or (for the situation of too much light) neutral density (ND) filters to correct the situation.

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  • Hello AbamboPictures, welcome to Photo.SE. I don't think your answer will help much as it explains the effects of camera settings (already covered in depth in other posts) instead of the possible sources of the problem. – Olivier Sep 25 '15 at 18:55

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