Nikon Coolpix S51c

Color (7.46)
All cameras reproduce colors slightly differently, which is why we test color accuracy. Some cameras oversaturate colors, making them vibrant but unnatural, while others can undersaturate colors, making them subtle but dull. We test color accuracy by photographing an industry standard GretagMacbeth ColorChecker test chart, and then compare the colors the camera reproduces with the known colors of the test chart. The ColorChecker chart is made of 24 different color tiles that represent various colors from around the color spectrum. The image below shows how the Nikon S51c’s colors match up the ideal colors of the ColorChecker. The outside squares show the colors the camera reproduces, the inner squares show the ideal colors of the ColorChecker corrected for exposure, and the small inner rectangles show the ideal ColorChecker colors under a perfectly even exposure. The S51c’s colors are most accurate when slightly underexposed.

Several of the color tiles match up very well with their ideal counterparts, but several of them do not. This is most apparent in the yellows and blues, where the yellows look rather greenish and the blues tend toward purple. This information is shown in a more quantitative way in the color space graph below. The squares represent the ideal color tile colors, while the circles show the corresponding colors the S51c reproduces. The lines connecting the squares and circles show the amount of color error for each color tile.

As you can see from the graph, a number of the yellows, greens, and blues are shifted away from their ideal values. Some of this may have been done on purpose; purple blues can make blue skies prettier, and greener yellows can make foliage look especially lush. However, these colors are shifted too much for our liking. Everyone likes pretty blue skies, but unless you’re Prince, you probably don’t want your photos to look like they were taken on a planet with purple skies. Also, there is a strong trend in all the colors to be undersaturated. This means the colors in your photos won’t be as vibrant as they could be, and will look rather dull. Overall, the S51c scores slightly below average in color accuracy.

Resolution (5.11)
We test resolution by photographing an evenly-lit industry-standard resolution test chart at varied focal lengths and exposure settings. We measure the resolution with Imatest, a powerful imaging analysis program that determines resolution in terms of line widths per picture height (lw/ph). These units represent the number of equally-spaced, alternating black-and-white lines that can fit across the frame before becoming blurred.

Click the chart to view the high resolution image

The 8-megapixel S51c shows its best resolution at ISO 100, f/3.7, and a focal length of 11mm. The camera resolves 1412 lw/ph horizontally with 1.6 percent oversharpening, and 1480 lw/ph vertically with 2.8 percent oversharpening. While it's good the camera doesn't drastically oversharpen photos, these numbers are unimpressive. Not only is the resolution poor, but the images show color fringing (even at the centers), lens vignetting (darkening) on the corners, white "ghosting" lines next to edges of high contrast, some blurriness at the edges, and evidence of noise, even at ISO 100. All in all, the S51c is not the sharpest camera you’ll find on the market today, though similarly-priced Nikon point-and-shoots, such as the Coolpix S510, don’t perform much better.

Noise – Manual ISO (3.07)
Digital images are always subject to image "noise,' the grainy or splotchy effect that can be seen in photos, especially at higher ISO speeds. We test noise levels by photographing our test chart under bright, even studio lights at every ISO speed available. Imatest measures noise by the percentage of image detail it drowns out.

The S51c is a noisy camera at all ISO speeds. Noise is apparent even at ISO 100, especially if the photos are viewed or printed large. The noise itself is scattered with colored splotches, which you can see up close by clicking on the still life images farther down the page. The blue noise is especially strong and gives photos a blue tint, especially at higher ISO speeds. At ISO 800 and 1600, it is apparent the photos have been "smoothed," meaning information is smoothed over to lessen the impact of the noise. Yet noise levels are still high, yielding images with nasty noise as well as less detail. This is one of the noisiest cameras we have seen this year.

Noise – Auto ISO (1.20)
We also set the camera to Auto ISO and photograph the test chart under the same conditions as above. The S51c chooses ISO 200 under the bright studio lights. This is normally a reasonable choice for this light level, but the S51c is quite noisy at ISO 200, yielding a poor Auto ISO score.

Still Life Sequences
Click to view the high resolution images

White Balance (3.85)
Good white balance accuracy is essential to producing attractive and accurate colors. Each type of light source has a different color cast, and cameras must be able to adjust accordingly. We test white balance by photographing the ColorChecker chart under four types of light: flash, fluorescent, outdoor shade, and tungsten. We test the Auto white balance setting, as well as the appropriate white balance presets found in the Shooting menu.

Auto (3.19)
Set to Auto white balance, the S51c’s accuracy is poor under all four types of light. Usually we would suggest just using the presets instead, but they hardly fare any better.

Auto WB - Flash Illumination

Auto WB - Fluorescent Illumination

Auto WB - Shade Illumination

Auto WB - Tungsten Illumination

Preset (4.51)
Using the white balance presets, the camera is fairly accurate under tungsten lights, but poor with the flash, in fluorescent light, and in outdoor shade. Depending on the subject you are shooting, you may very well notice odd color casts to your photos with this camera. The only way to really make this go away is by manually white balancing with a white card.

Flash WB - Flash Illumnation

Fluorescent WB - Fluorescent Illumination

Shade WB - Shade Illumination

Tungsten WB - Tungsten Illumination

Low Light (5.40)
Not all your shooting will be done in brightly lit conditions, which is why we also test camera performance in low light. We dim the studio lights to 60, 30, 15, and 5 lux to test the limits of camera sensors. Sixty lux corresponds to the amount of light in a room lit softly by two table lamps, 30 lux is about as bright as a room lit solely by a 40-watt bulb, and 15 and 5 lux are very low light that test the limits of a sensor. All shots are taken at ISO 1600.

Low Light Tests
60 Lux	30 Lux
15 Lux	5 Lux

The S51c cannot quite expose properly at 5 lux, showing that the camera has its limits, even at such a high ISO speed. Noise levels are very high in low light, though color accuracy stays quite even.

We also test performance at long shutter speeds, but only at ISO 400. The slowest shutter speed we could get the S51c to use at ISO 400 was 1 second, where it showed significant noise and poor color accuracy. It can also be difficult to expose properly in dimly lit situations because the S51c has no options for metering. This camera can capture non-blurry photos in low light, but they aren’t going to look great.

Dynamic Range (5.24)
Dynamic range is a measure of a camera’s tonal range, i.e. the range of gray tones it can discern. High dynamic range is especially important in scenes with high contrast, such as a photo of a building in bright sunlight that has both bright highlights and dark shadows. A camera with poor dynamic range blows out the highlights and fails to show any detail in the shadows. We measure dynamic range by photographing a backlit Stouffer step chart at all ISO speeds. The Stouffer chart is made up of a long row of gray rectangles, varying in tone from brightest white to darkest black. The more rectangles a camera can detect, the better its dynamic range.

The S51c has decent dynamic range at ISO 100, but then drops steadily at higher ISO speeds. As is the case with most cameras, keeping the S51c at ISO 100 whenever possible produces the nicest looking photos. Dynamic range is linked closely with noise levels because noise hides subtle tonal variations, hurting dynamic range. Many point-and-shoot cameras have trouble with dynamic range, and the S51 performs slightly below average for the year.

Speed/Timing – All speed tests were conducted using a Kingston Ultimate 120X 2GB SD Card, with the camera set to highest resolution and best quality, unless otherwise noted.

Startup to First Shot (3.0)
Not only does the small size of the S51c's on/off button make it quite hard to turn on, but there is a lengthy delay before you can take a photo. We measured at least 7 seconds from the time the button was pressed until the photo was taken photo, though it is quite inconsistent.

Shot-to-Shot (8.8)
The S51c has two continuous shooting modes, Continuous and Multi-Shot 16. In Continuous mode, the camera takes photos every 1.2 seconds for more than100 shots. It is nice that the length isn’t limited, but 1.2 seconds between shots won’t allow you to capture much dramatic action, especially if it happens quickly – like a baseball swing.

Shutter-Shot (8.8)
The S51c has a 0.1-second delay, even when prefocused, and a 0.7-second delay when not prefocused.

Processing (5.4)
The camera takes 2.3 seconds to process on 3.2 MB photo taken at ISO 125.

Video Performance (3.94)
Bright Indoor Light – 3000 lux
We capture footage of our color charts with studio lights adjusted to 3000 lux. The S51c has tremendous color error, and there is no way to adjust white balance in Movie mode. Noise levels, however, are quite low.

Low Light – 30 lux
In low light, color error is also extremely high. Noise levels are quite high, as well, partly due to the fact the camera has trouble exposing properly in low light.

Resolution
We also capture footage of the resolution test chart. In highest quality video mode, the S51c records 147 lw/ph horizontally with 24 percent undersharpening, and 487 lw/ph vertically with 11 percent undersharpening. Such a large disparity between horizontal and vertical sharpness is quite unusual, and you can see its effect in the two crops below.

Outdoor Motion
We take cameras outside to see how they capture moving cars and pedestrians. The S51c has nice color and exposure, but suffers from a soft focus, motion moiré, blue shadows, some evident noise, and some jerkiness to objects moving off the frame. This camera is further evidence that digital camera video is still nowhere near camcorder quality.