Almost every review of the Nikon D7100 contains glowing reports about the camera’s picture quality. As you’ve no doubt discovered, those claims are true: This baby can create large, beautiful images. What you may not have discovered is that Nikon’s default Image Quality setting isn’t the highest that the D7100 offers.
Why would Nikon do such a thing? Why not set up the camera to produce the best images right out of the box? The answer is that using the top setting has some downsides. Nikon’s default choice represents a compromise between avoiding those disadvantages while still producing images that will please most photographers.
Picture quality is not about the composition, exposure, or other traditional characteristics of a photograph. Instead, picture quality refers to how finely the image is rendered in the digital sense. The figure illustrates the concept: The first example is a high-quality image with clear details and smooth color transitions. The other examples show five common image defects.
Each of these defects is related to a different issue, and only one is affected by the Image Quality setting on your D7100. So if you aren't happy with your image quality, first compare your photos to those in the figure to properly diagnose the problem. Then try these remedies:
Pixelation: When an image doesn’t have enough pixels (the colored tiles used to create digital images), details aren’t clear, and curved and diagonal lines appear jagged. The fix is to increase image resolution, which you do via the Image Size control.
JPEG artifacts: The “parquet tile” texture and random color defects that mar the third image can occur in photos captured in the JPEG (jay-peg) file format, which is why these flaws are referred to as JPEG artifacts. This is the defect related to the Image Quality setting.
Noise: This defect gives your image a speckled look, as shown in the lower-left example. Noise can occur with very long exposure times or when you choose a high ISO Sensitivity setting on your camera.
Color cast: If your colors are seriously out of whack, as shown in the lower-middle example in the figure, try adjusting the camera’s White Balance setting.
Lens/sensor dirt: A dirty lens is the first possible cause of the kind of defects you see in the last example in the figure. If cleaning your lens doesn’t solve the problem, dust or dirt may have made its way onto the camera’s image sensor.
Your D7100 offers an automated sensor-cleaning mechanism (you control its operation via the Clean Image Sensor command on the Setup menu). But if you frequently change lenses or shoot in a dirty environment, the internal cleaning mechanism may not be adequate, in which case a manual sensor cleaning is necessary.
You can do this job yourself, but I don’t recommend it. Image sensors are delicate beings, and you can easily damage them if you aren't careful. Instead, find a local camera store that offers this service. Sensor cleaning typically costs about $50, but some places offer the service free if you bought the camera there.
When diagnosing image problems, you may want to open the photos in ViewNX 2 or some other photo software and zoom in for a close-up inspection. Some defects, especially pixelation and JPEG artifacts, have a similar appearance until you see them at a magnified view.
The flaws in the example images are exaggerated to make the symptoms easier to see. With the exception of an unwanted color cast or a big blob of lens or sensor dirt, these defects may not even be noticeable unless you print or view your image at a very large size.
And the subject matter of your image may camouflage some flaws; most people probably wouldn’t detect a little JPEG artifacting in a photograph of a densely wooded forest, for example.
Any digital camera can produce these defects under the right circumstances.