A method for helping to control a vehicle occupant protection device (22) includes taking an image of the vehicle interior with a digital imager (50) having an array of pixels (53). A contiguous portion of the image less than the entire image is selected. At least one image enhancement technique is applied to the selected image portion. The enhanced image portion is combined with the other portions of the image to make an enhanced image. The enhanced image is analyzed to detect at least one of features and characteristics of the enhanced image. Alternatively, a selected non-contiguous group of the pixels (53) of the imager (50) are read out, as representative of the entire image, to estimate the illumination levels across the entire array of pixels. In one aspect, the imager shutter (56) speed may be controlled to enhance the image.