Nikon S4 Exposure

Saturation & Hue Accuracy
Oversaturated color (especially reds and blues), very typical of consumer digital cameras. Slight color casts, depending on the white balance setting.

Most consumer digital cameras produce color that's more highly saturated (more intense) than found in the original subjects. This is simply because most people like their color a bit brighter than life. The Coolpix S4 does oversaturate color a fair amount, especially with strong red and blue tones. Where oversaturation is most problematic is on Caucasian skin tones, as it's very easy for these "memory colors" to be seen as too bright, too pink, too yellow, etc. The Coolpix S4 did render skin tones a bit pink in most cases, particularly indoors, though skin tones outdoors showed slightly more orange.

The other important part of color rendition is hue accuracy. Hue is "what color" the color is. Here, the Coolpix S4 performed within acceptable boundaries, though the camera's white balance setting frequently skewed the color balance slightly. For example, the Manual white balance often tended toward a slight magenta tint, while the Auto setting often resulted in a warmer cast. So results where hue is concerned will depend somewhat on the lighting and white balance setting.

The bottom line, of course, is how well the camera does with "real-world" subjects, and we think that the results there would be quite pleasing to most consumers.

Exposure and White Balance

Indoors, incandescent lighting
Moderate warm cast with the Incandescent white balance setting, though good color with the Manual setting. About average exposure compensation required.

Color balance indoors under incandescent lighting was rather reddish in Auto white balance mode. Both the Incandescent and Manual settings handled the challenge much better, though the Incandescent setting had a slight warm cast. Results are a hair pinkish with the Manual option, but most pleasing overall. The Coolpix S4 required a +1.0 EV exposure compensation boost to get a good exposure, which is about average for this shot. Overall color is good, though skin tones are pinkish and the blue flowers are dark and purplish. (A very common outcome for this shot.) Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulb, a pretty yellow light source, but a very common one in typical home settings here in the US.

Outdoors, daylight
Good color balance, but a tendency to overcompensate for harsh highlights. High contrast and often more positive exposure compensation required than average.

Outdoor shots typically showed high contrast with blown-out highlights and very deep shadows. Detail in the shadows was also weak, with high noise and little definition. Exposure accuracy overall was a little below average, the camera requiring slightly more exposure compensation than we're accustomed to seeing with consumer digicams. In the outdoor house shot above, the overall exposure appears actually a little dim at the default setting, despite the strongly blown-out highlights.

See full set of test images with explanations
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Resolution
Average resolution for its 6-megapixel resolution, 1,200 lines of strong detail.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,200 lines per picture height (perhaps 1250 lines in the horizontal direction), with extinction at around 1,600. (The camera did produce slight color artifacts at lower line frequencies, visible in the full-sized res target shots.) This is probably on the low side of average among the 6-megapixel cameras we've tested. Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail. Beware that while you might be able to make out what looks like distinct lines at numbers higher than those we've mentioned here, the camera is just doing its best to continue interpreting the lines. If you zoom in and follow them from the wider portions, you'll see the lines converge and reappear several times, so the lines you see at 1,500 and higher are really only artifacts generated by the camera's imaging system.

See full set of test images with explanations
See thumbnails of all test and gallery images

Sharpness & Detail
Moderately sharp images, with a fair amount of blurring from noise suppression and noise itself.

The Coolpix S4's images are only moderately sharp. The camera over-sharpens high contrast subjects, producing slight "halos" of artificially enhanced contrast, as seen in the bright leaves and white trim above. (Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.)

Noise-suppression systems in digital cameras tend to flatten-out detail in areas of subtle contrast. The effects can often be seen in shots of human hair, where the individual strands are lost and an almost "watercolor" look appears. The crop above right shows this, with darker areas of Marti's hair showing only limited detail. Image noise also reduces definition in areas like this, noticeable in the deeper shadows above.

ISO & Noise Performance
Some visible noise even at low sensitivity settings, high noise that blurs detail and causes visible colored noise artifacts at the higher settings.

Even the Coolpix S4's lower ISO settings produced some visible image noise in the shadows, but it's within a range that most users will probably find acceptable. As the ISO setting increases, so does the noise level and the amount of blurring that results. At ISO 200, details are softer, and its images at ISO 400 are quite soft with bright noise pixels. When printed though, the impact of the noise seemed less severe. While some colored noise artifacts were visible in 8x10 inch prints at ISO 400, we think the results would be acceptable for many users, particularly for prints to be displayed on a wall or table, and viewed at distances of a foot or more. At a size of 5x7 inches, ISO 400 results should be acceptable to most anyone.

Extremes: Sunlit and low light tests
High resolution with good overall detail, but high contrast and very limited shadow detail. Moderate low-light performance, capable of capturing bright images under average city street lighting and slightly darker conditions.

Sunlight:
Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here.)

The Coolpix S4 responded to the deliberately harsh lighting of this test with very high contrast, losing detail in both highlights and deep shadows. Noise suppression is visible in both shadows and highlights as well, contributing to the loss of detail, particularly in shadow areas. The best overall exposure was obtained with a +1.3 EV exposure adjustment, though the highlights are really much too bright. Still, at +1.0 EV, the overall exposure was just a little too dim. (In "real life" of course, be sure to use fill flash in situations like the one shown above; it's better to shoot in the shade when possible.)

Low light:
Our low light testing revealed some limitations in the lens and sensor's ability to gather and process light, but the Coolpix S4's performance in this area should be adequate for most consumers. With a maximum shutter speeds of two seconds, the Coolpix S4 only captured bright images to about 1/2 foot-candle, at the 200 and 400 ISO settings. At ISOs 50 and 100, images were only bright to about one foot-candle (about the equivalent of average city street lighting at night). Color balance was pretty good with the Auto white balance setting. The camera's autofocus system worked well enough for its exposure system, able to focus on the subject down to the 1/4 foot-candle with the AF assist turned off. With AF assist on, the AF system worked well past the lowest light level we test at. Overall, while the S4 won't let you shoot by moonlight, it should easily handle typical city night scenes.

Coverage and Range
Pretty good flash range, considering the long zoom lens. Slightly uneven coverage at wide angle, very even at telephoto. Flash is reasonably well color-balanced to incandescent room lighting. Our standard shots required about average exposure compensation.

Flash coverage was only a little uneven at wide angle, though poor at full telephoto. In the Indoor test, the flash on the Coolpix S4 underexposed our subject at its default setting, requiring a +1.0 EV exposure compensation adjustment to get bright results. Overall color is pretty good, though slightly pinkish. The camera's Slow-Sync flash mode produced slightly brighter and more even results, though with a stronger pinkish-orange cast from the room lighting. It required less exposure compensation due to the longer shutter speed, at +0.7 EV.

The Coolpix S4's flash remains bright to about 11 feet, decreasing in intensity from there. The test target is still quite visible at 14 feet, however, just with lower flash intensity.

Print Quality
Good print quality, great color, very usable 11x14 inch prints. ISO 400 images are a bit soft with noise artifacts at 8x10, quite acceptable at 5x7, great at 4x6.

Testing hundreds of digital cameras, we've found that you can only tell just so much about a camera's image quality by viewing its images on-screen. Ultimately, there's no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon i9900 studio printer, and on the Canon iP5000 here in the office. (See the Canon i9900 review for details on that model.)

With the Nikon Coolpix S4, we found that it had enough resolution to make very crisp 8x10 inch prints. At 11x14, its prints were a bit softer looking, but more than adequate for wall or table display. At high ISO levels, image noise levels increase, and sharpness suffers slightly. ISO 200 photos look fine printed at 8x10 inches, but ISO 400 ones show a few colored artifacts at that size, and are slightly softer. Most users will probably find 8x10 prints from ISO 400 images usable for wall or table display, but for best results, print them at 5x7 inches or below. Color-wise, the Nikon S4's images looked great when printed on the i9900, with very bright, vibrant color. Users who prefer more subdued, technically accurate color saturation levels may find the S4's images a little too bright, but most consumers will probably find the Nikon Coolpix S4's bright, snappy images very appealing.