D90 shutter Mode

Help, I am under the assumption that shooting in Shutter Mode (S) solves the exposure triangle by first making sure the shutter speed is at the value I set and then solving for ISO and f-stop. However when I shoot, the camera often changes the shutter speed below the value I set. Why is this happening?
Thanks

Probably because there is not sufficient light for the ISO you choose or the maximum aperture that your lens has. I'm not certain, but usually when this occurs the shutter speed will be displayed in red in the viewfinder.

You could try using auto-iso setting to let the camera bring the iso up to your set limit in the auto-iso menu, or accept that low light doesn't allow for the shutter speed you want to use.

Welcome to the forum,Marcel beat me to it,S is not a full auto setting you need to be setting an aperture or ISO that can give you the shutter speed you want.

kennydrx7 said:

Help, I am under the assumption that shooting in Shutter Mode (S) solves the exposure triangle by first making sure the shutter speed is at the value I set and then solving for ISO and f-stop. However when I shoot, the camera often changes the shutter speed below the value I set. Why is this happening?
Thanks

Click to expand...

Welcome to the forum.

Shutter speed is supposed to be fixed in S or M mode, whatever you set should not change unless you change it. However, if you also select Bracketing (exposure bracketing), then of course something has to change on each shot to accomplish this. Turn bracketing off, D90 manual page 92.