Nikon D7000 manual High ISO NR

Chapter 8 ■ Setup: Playback and Shooting Menus 265

■On. When exposures are eight seconds or longer, the Nikon D7000 takes a sec- ond, blank exposure to compare that to the first image. (While the second image is taken, the warning Job nr appears on the monochrome LCD panel and in the viewfinder.) Noise (pixels that are bright in a frame that should be completely black) in the “dark frame” image is subtracted from your original picture, and only the noise-corrected image is saved to your memory card. Because the noise-reduction process effectively doubles the time required to take a picture, you won’t want to use this setting when you’re rushed. Some noise can be removed later on, using tools like the noise reduction features built into Bibble Pro, many image editors, or Nikon Capture NX2.

High ISO NR

Noise can also be caused by higher ISO sensitivity settings, and the Nikon D7000, which offers settings up to ISO 6400 (and thence up to the equivalent of ISO 12800 and 25600 with the Hi 1.0 and Hi 2.0 settings) has a loftier ISO ceiling than many cameras. Even so, high ISO noise reduction, which can be set with this menu option, may be a good option in many cases. You can choose Off when you want to preserve detail at the cost of some noise graininess, and the D7000 will apply high ISO NR only at the “boosted” settings of Hi 0.3 and above. Or, you can select On, which is applied when ISO sensitivity has been set to ISO 800 or higher.

The effects of high ISO noise are something like listening to a CD in your car, and then rolling down all the windows. You’re adding sonic noise to the audio signal, and while increasing the CD player’s volume may help a bit, you’re still contending with an unfa- vorable signal to noise ratio that probably mutes tones (especially higher treble notes) that you really want to hear.

The same thing happens when the analog image signal is amplified: You’re increasing the image information in the signal, but boosting the background fuzziness at the same time. Tune in a very faint or distant AM radio station on your car stereo. Then turn up the volume. After a certain point, turning up the volume further no longer helps you hear better. There’s a similar point of diminishing returns for digital sensor ISO increases and signal amplification as well.

As the captured information is amplified to produce higher ISO sensitivities, some ran- dom noise in the signal is amplified along with the photon information. Increasing the ISO setting of your camera raises the threshold of sensitivity so that fewer and fewer photons are needed to register as an exposed pixel. Yet, that also increases the chances of one of those phantom photons being counted among the real-life light particles, too.

Fortunately, the Nikon D7000’s CMOS sensor and its EXPEED digital processing chip are optimized to produce the low noise levels, so ratings as high as ISO 1600 to ISO 3200 can be used routinely (although there will be some noise, of course), and even