This question already has an answer here:
I've got a D-90 Nikon and a f1.4 lens and I've found in very bright areas like beaches in the Caribbean, when I have the camera doing auto ISO and speed and fixed f-stop, sometimes I get overexposed pictures.
These are shot at 1/4000 of a second and ISO 200, which appear to be the limits. Other than turning down my f-stop, is there anyway to configure this camera to avoid this situation? I presume 1/4000 is the limit on shutter exposure, but what about ISO? I would think a setting below 200 should be possible, but I don't seem to be getting it. There are HI and LO settings when you set ISO manually, but I do not know what these mean nor why they are not used by the auto-ISO setting.