Metering
Nikon’s 1,005-pixel metering system, which has been used in a number of cameras over the past few years, has been dramatically upgraded for the D4. It now features 91,000 pixels, which does beg the question of how detailed a sensor needs to be to produce a good exposure.
I can see very little difference between the exposures of the D3S and the D4 in matrix metering mode, and you may wonder why such a high-resolution sensor is needed. However, the new 91,000-pixel sensor does more than just meter the light.
Nikon uses a scene-based metering system that is capable of recognising elements in front of the lens, such as faces, and then picking a suitable exposure. The higher the resolution of the sensor, the more likely it is to be able to see such details and adjust the exposure accordingly. So while the sensor does measure light, its real benefit with regard to exposure is recognising scenes. This sensor is also used to measure white balance, so again, the more detail and information available, the better.
Overall, the system works well, with the camera producing good exposures. When shooting landscapes, for instance, I found that the evaluative metering was generally intelligent enough to avoid blowing out highlight detail. This did sometimes lead to the foreground being slightly underexposed, and I took one sequence of images that had a +0.7EV exposure greater than the metered setting. It is, nevertheless, quite easy to predict what the metering will do and, anyway, the slight underexposure can be beneficial in preserving highlight detail that, once lost, cannot be recreated.
