Nikon D90

Color (9.98)
Few of us can resist the siren call of Photoshop's cornucopia of color-enhancing contrivances.  Our laboratory testing, though, focuses on how well a given camera delivers an accurate depiction of the colors we saw through the viewfinder. If you want to give  your pink hearts, yellow moons, orange stars and green clovers a supersaturated glow after the fact, that's absolutely your perogative, but for starters you deserve a photo that provides images as realistic as they are magically delicious. And the Nikon D90 does a nice job in this regard, as long as you change from the default Picture Control setting. Nikon Picture Controls are useful one-step combinations of hue, saturation, sharpness and other settings. The default, called Standard, produces photos that are pleasing to the eye, but not necessarily to our Imatest image analysis software program, which stresses accuracy over visual delight. With this in mind, we changed the D90 to the Neutral Picture Control setting before shooting an industry-standard Gretag-Macbeth color chart for test purposes.

In addition to a statistical result, Imatest produces a pair of charts that visually convey the camera's color accuracy performance. In the chart below, the color as captured by the camera is shown in the outer rectangles, the color with luminance correction applied is shown in the larger inset rectangle, and the original chart color is reproduced in the smaller inset rectangle.

The Gretag-Macbeth color chart

The chart below uses a more structured system for representing color accuracy. Here the ideal colors from the chart are represented by the squares, the colors captured by the camera are shown in the circles, and the lines connecting the two indicate how relatively close the two values lie.

As you can see, the D90 did very well across the board, particularly in the realm where flesh tones are likely to fall. And if you happen to have blue-toned friends, even their portraits won't be appreciably far off the mark.

Another point worth mentioning here is the consistency we found in color reproduction across the entire ISO range. There's barely a budge in color error figures shooting anywhere from ISO 200 to 3200, and even the pumped-up Hi ISO settings beyond 3200 aren't so far off that you'd be likely to notice the difference visually.

The short lines here indicate good color accuracy.

Resolution (11.01)
There's a lot more to achieving image sharpness than throwing massive numbers of megapixels at the problem. Final image resolution is affected by the sensor, camera optics, digital processing and, it sometimes seems, phases of the moon. In our testing (conducted during daylight hours in a darkened lab to minimize lunar interference), we shoot an industry-standard resolution chart under bright studio lighting at the full range of ISOs supported by the camera, and at several distances. We run the resulting photos through Imatest, which analyzes the results and provides a statistical representation of image resolution in line widths per picture height, or lw/ph.

The D90 resolution results are very good, topping out at 1915 lw/ph horizontally when shooting with the 18-105mm lens. According to Imatest, the Nikon consistently undersharpened the images produced, particularly when shooting at the longer end of the zoom range. This means you have some freedom to add crispness if desired using computer software, without introducing obtrustive artifacts to the image.

Actual size reproduction of a D90 resolution chart image

Our comparison shows the D90 resolution results are comparable to the other cameras in the lineup, midway between the two Nikons that bookend the D90 in price and lagging the Canon, but not by much.

White Balance (9.58)
A piece of white paper looks white to our eyes under a wide variety of light sources, when in fact the color of the illumination from the sun, for example, and a fluorescent lamp are radically different. Our brains make the adjustment automatically. If you look at a photo and the white surfaces look greenish, or orange-tinged, though, you won't be quite as forgiving. It's up to a camera's white balance system to compensate for the varying types of lighting when capturing an image, one of the most technically demanding aspects of the digital photography system.

Nearly every camera offers two methods for making white balance adjustments. First, there's an automatic system that meters the scene and tries to adjust to perceived lighting conditions. Second, the manufacturer provides white balance presets to adjust for different lighting conditions, which the user selects manually. We test each of these systems in our labs, shooting under flash, fluorescent, daylight shade and tungsten illumination. The third method for setting white balance adjustment, found on most SLRs and some relatively sophisticated compact cameras, lets you shoot a neutral grey or white surface under the target lighting conditions and have the camera set the white balance adjustment based on this known point of reference. We use this technique (for cameras that offer it) during our lab testing for other performance factors, but don't test its accuracy separately.

Auto White Balance (9.88)
The overall high score for the automatic white balance system, which averages performance under the four tested lighting conditions, is somewhat unbalanced by the camera's exceptional accuracy when shooting under fluorescent lighting. This is often a sticking point, yet the D90 aced the test. However, the automatic system did an awful job adjusting for a shaded daylight environment, and its performance under tungsten illumination was also less than stellar. Fortunately, as shown below, the manual presets for these latter environments did an excellent job in these problem areas. Note that the results shown below are exaggerated to show color differences, and don't represent the actual differences you'd see in your own photos.

Exaggerated White Balance Errors

Auto WB - Flash Illumination

Auto WB - Fluorescent Illumination

Auto WB - Daylight illumination

Auto WB - Tungsten illumination

Preset (9.28)
Using the preset white balance options produced acceptable performance across the board, with exceptionally good results under shady conditions and tungsten illumination. It's worth noting that the D90 white balance presets are fully customizable so, if you're not satisfied with the results produced in a test shot, it's fast and easy to tweak the settings using the four-way controller and re-shoot until you're satisfied.
 

Exaggerated White Balance Errors (Presets)

Flash Preset WB - Flash Illumination

Florescent Preset WB - Fluorescent Illumination

Cloudy Daylight preset WB - Daylight illumination

Tungsten preset WB - Tungsten illumination

On balance, the D90 outscored all of our comparison cameras on the white balance test. In practice, based on our findings, the smart move is to stick with auto mode in the shade and under fluorescent lights, and take the extra moment to choose the presets when shooting under household tungsten bulbs or outdoors in the shade.