There is no need to raise the ISO to 1600 in order to shoot an utterly still subject at 1/2000th of a second. This must be mistaken choice of ISO, because it causes very heavy noise in the shadow areas that make the image coarse and distracts from its quiet content. If you look at the LCD viewfinder, you will see all of your settings displayed when you press the shutter half way down. If you make it a practice to always check that display, you can catch mistakes like an ISO 1600 and 1/2000th shutter speed before you make the the picture and correct the settings accordingly.
