Random ISO's when shooting indoors

barnack

When I shoot in S or A modes, setting a normal shutter speed or aperture and ISO 100 all seems fine. The photos turn out as expected.

When I review the image data and histogram on the review screen the ISO for the frame is in red and a stupid figure like 1600 or 3200. I'm not shooting in poor light, often near a window or in the conservatory, so why on earth would the camera decide it needs to ramp up the ISO that high? I have the latest firmware version.

Moose

Howdy @barnack - I'm guessing you have Auto ISO enabled. It's a bit confusing, but the D3100 will display "100" on the LCD info panel when Auto ISO is turned on. You can do a couple things to remedy this...

1. Turn off Auto ISO - Access the Menu,navigate to the Shooting Menu and highlight ISO sensitivity settings and turn off Auto ISO Sensitivity

2. Set the Max Sensivity for Auto ISO - In the same menu, you can set the maximum sensitivity for the D3100 to use when Auto ISO is enabled.

As for the Nikon D3100 choosing high ISO's sensitivities while using Auto ISO...this is completely normal. When shooting indoors, hand-held, the D3100 is trying to get a shutter speed fast enough to freeze subject movement and to reduce the effects of camera shake.

If you're shooting motionless subjects (monuments, paintings, interiors, etc...) then you can force an ISO of 100 to reduce image noise (grain)...just make sure you mount your D3100 to a tripod to eliminate the chance of camera shake. Happy shooting! :)

barnack

Many thanks! I will check to make sure it is not in Auto. I recall setting it to 100, but as I said will check again.