Since the background is gray in the image and white in reality, the images are under exposed. Dialing in some positive Exposure Compensation should solve the problem. As stated a above, when the background is white or brighter than the subject, the cameras metering system tends to under expose when Matrix or even Center Weighted metering is used. Depending on the subjects size, using Spot Metering should be more accurate. Good Luck and Enjoy your Nikons!