Nikon D5100 Image Quality

Saturation & Hue Accuracy
Very good overall accuracy and saturation, with only minor shifts in hue and intensity.

In the diagram above, the squares show the original color, and the circles show the color that the camera captured. More saturated colors are located toward the periphery of the graph. Hue changes as you travel around the center. Thus, hue-accurate, highly saturated colors appear as lines radiating from the center. Click for a larger image.

Saturation. The Nikon D5100 pushes dark blues and some darker greens moderately, but actually undersaturates some yellow and cyan tones slightly. Red and orange are also pushed very slightly, but not as much as most cameras. Overall, saturation levels are quite accurate, just slightly higher than the D3100, D5000 and D7000. 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.

Skin tones. Here, the Nikon D5100's Caucasian skin tones looked just about right in outdoor lighting using auto white balance, perhaps just slightly warm. Manual white balance produced slightly pinker tints, which had a "healthier" look. 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.

Hue. The Nikon D5100 showed a few small color shifts relative to the mathematically precise translation of colors in its subjects, but its overall color accuracy was very good. Reds were shifted slightly toward orange, cyan was shifted toward blue, and there were slight shifts in some oranges, greens and purples, but shifts were relatively minor. (The cyan to blue shift is very common among the digital cameras we test; we think it's a deliberate choice by camera engineers to produce better-looking sky colors.) Hue is "what color" the color is.

Picture Control
The Nikon D5100 offers six preset "Picture Control" options. You can adjust Sharpening, Contrast, Brightness, Saturation and Hue for any of the settings. (For Monochrome, Saturation and Hue are replaced by Filter Effects and Toning settings.)

Mouse over the links above to see the effect of the presets on our Still Life target. Click on a link to load the full resolution image.

Saturation Adjustment
The Nikon D5100 lets you adjust the image saturation and contrast in seven steps each, brightness in three steps, hue in seven steps and sharpening in ten steps. As can be seen below, the saturation adjustment worked very well, providing a reasonably fine-grained adjustment over a useful range of control. The saturation adjustment also has almost no impact on contrast. That's how a saturation control should work, but we've often found interactions between saturation adjustments and image contrast (and vice versa) on the cameras we test.

Saturation Adjustment Examples
-3	-1	0	+1	+3

The series of shots above shows results with several different saturation adjustment settings, showing the minimum step size around the default, as well as both extremes. There is also an Auto setting available. See the Thumbnails index page for more (look for the files named D5100OUTBSATx.JPG). Click on any thumbnail above to see the full-sized image.

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

Exposure and White Balance

Indoors, incandescent lighting
Very warm results with Auto and Incandescent white balance, though good color with Manual white balance setting. Slightly above average exposure compensation required.*

Auto White Balance +0.7 EV	Incandescent White Balance +0.7 EV
Manual White Balance +0.7 EV

Indoors, under normal incandescent lighting, color balance was very warm and reddish with the Auto white balance setting. (We'd say unacceptably so.) The Incandescent setting was also too warm and yellowish for our tastes. (Some users may prefer this look, though, as being more representative of the original lighting.) The Manual white balance setting by far produced the most accurate results, if just a touch cool. The Nikon D5100 does not offer a Kelvin color temperature setting as found in its higher-priced siblings. The D5100 required slightly above average exposure compensation for this shot (+0.7 EV). The average needed among cameras we've tested for this shot is +0.3 EV. Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.

Outdoors, daylight
Good color outdoors with very good highlight/shadow detail preservation. Options like Active D-Lighting and contrast adjustment are a help when faced with tough conditions like these.

Manual White Balance, +1.0 EV	Auto White Balance, 0 EV

The Nikon D5100 handled tough outdoor lighting under harsh sunlight well, producing good overall color. We found skin tones a touch warm in our "Sunlit" Portrait shot with Auto white balance, preferring the Manual white balance results here, while in our Far-field House shot, Auto white balance was a touch cool. Default contrast was a bit on the high side (as most users prefer), but shadow and highlight detail in the Portrait shot shown above was quite good. Despite the bright appearance, only a few highlights mainly in the red and blue channels were clipped in the model's shirt, pendant and some of the flowers. The blue channel was lost in some of the deeper shadows, but shadow noise was very low. The +1.0 EV exposure compensation required to keep the mannequin's face bright was slightly above the +0.7 EV average for this scene, though the Far-field House shot was well exposed at 0 EV, clipping only a few highlights in the white trim. Again, detail in the shadows was very good, and shadow noise very low.

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

Resolution
Very high resolution, ~1,900 lines of strong detail from JPEGs, ~2,000 from converted RAW files.

Strong detail to ~1,900 lines horizontal Camera JPEG	Strong detail to ~1,900 lines vertical Camera JPEG
Strong detail to ~2,000 lines horizontal VNX processed RAW	Strong detail to ~2,000 lines vertical VNX processed RAW
Strong detail to ~2,000 lines horizontal ACR processed RAW	Strong detail to ~2,000 lines vertical ACR processed RAW

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,900 lines per picture height in the horizontal direction, and about 1,900 lines per picture height in the vertical direction in JPEGs. (Some might argue for over 1,900 lines, but aliasing artifacts begin to appear before 2,000 lines.) Complete extinction didn't occur until around 3,000 lines in both directions. We were able to eke out a bit more resolution (about 2,000 lines) with RAW files processed through ViewNX 2 and Adobe Camera Raw 6.4, and both RAW conversions extended the extinction point of the pattern well beyond the in-camera JPEG. We did notice the ACR 6.4 conversions contained more color moiré than the camera or ViewNX images, and it also produced some jagged edges in diagonal lines, so the camera's processing is doing a pretty good job. 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.

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

Sharpness & Detail
Very good detail but a hint soft straight from the camera, with relatively minor edge-enhancement on high-contrast subjects. Minimal noise suppression artifacts at base ISO.

Very good definition of high-contrast elements, with only minor evidence of edge enhancement.	Subtle detail: Hair Noise suppression tends to blur detail in areas of subtle contrast, though detail remains strong in the darker parts of the model's hair here.

Sharpness. The Nikon D5100 produced very good detail, but there's a slight softness in its images overall, even when using the sharp Nikon 35mm f/1.8G prime lens at f/8 as was used for the house crop above left. F/8 is slightly beyond the diffraction limit on the D5100, but our testing on SLRgear showed that the sharpness loss from f/5.6 to f/8 was very slight: So the slight softness here is almost certainly the result of the camera's low pass filter and its image processing, rather than any loss optically. Some minor edge enhancement artifacts are visible on high-contrast subjects such as the crop above left, but overall results are still very good. Edge enhancement creates the illusion of sharpness by enhancing color and tonal differences right at the edge of a rapid transition in color or tone.

Detail. The crop above right shows only minimal detail loss due to noise suppression, as the darker areas of the model's hair show a lot of detail. Individual strands are still distinguishable even in the lighter shadows, though they begin to merge as shadows deepen, and in places where the tone and color of adjacent strands is very close. All in all, a very good performance here. 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.

RAW vs In-Camera JPEGs
As noted above, the Nikon D5100 does a pretty good job at capturing lots of detail, but JPEG images are slightly soft at the default settings. A little more detail can be obtained from carefully processing RAW files, though, without introducing additional artifacts. Take a look below, to see what we mean:

In the table above, mousing over a link at the bottom will load the corresponding crop in the area above, and clicking the link will load the full resolution image. Examples are all shot at ISO 100, and include in-camera Fine JPEG, the RAW file processed through Nikon's free ViewNX version 2.1.2 software, and the RAW file processed through Adobe Camera Raw (ACR) version 6.4, then sharpened in Photoshop. We used default settings for ViewNX. For ACR, we found best results by disabling sharpening in ACR, and sharpening instead in Photoshop with strong but tight 350% unsharp masking with a 0.3 pixel radius.

As is frequently the case, the demosaicing in Adobe Camera Raw and sharpening in Photoshop deliver finer detail than either the camera or the manufacturer's own software. Looking very closely at the images, ACR extracts a bit more detail that wasn't present in the JPEGs from either the camera itself or Nikon's software package, but the main difference is in the fineness of the rendering. Fine details (the tree branches against the sky, for example) look a little coarser in the various Nikon renderings than in that from ACR/Photoshop. This isn't without cost, though: While they don't look as crisp, the Nikon renderings are smoother-looking with less visible noise. We'd personally go the Adobe (or other high-quality third-party RAW converter) route here if we were concerned about making the sharpest-looking print possible from the D5100's files.

ISO & Noise Performance
Very good handling of noise vs detail to ISO 1,600.

Noise Reduction = Default
ISO 100	ISO 200	ISO 400
ISO 800	ISO 1,600	ISO 3,200
ISO 6,400	ISO 12,800	ISO 25,600

The Nikon D5100's noise performance is very similar to that of the D7000. Images were very clean at ISO 100 through 800, which just a touch of luminance noise becoming more visible in the shadows as ISO increased. Detail was still very good at ISO 1,600, with a tight film-like noise "grain" and very little fine detail lost to noise reduction. At ISO 3,200, subject detail takes a bigger drop than previous steps, with stronger blurring and more visible noise "grain", but detail is better than average. Images at 6,400 and ISO 12,800 are notably less detailed than those at lower sensitivity levels, with more visible noise reduction artifacts. ISO 25,600 shows a lot more chroma noise, in the form of yellow and purple blotches which also darkens the image. Of course, the impact of noise and detail loss are highly dependent on the size the photos are printed at, and pixel-peeping on-screen has surprisingly little relationship to how the images look when printed: See the Print Quality section below for recommended maximum print sizes at each ISO.

A note about focus for this shot: We shoot this image at f/4, using one of three very sharp reference lenses (70mm Sigma f/2.8 macro for most cameras, 60mm f/2.8 Nikkor macro for Nikon bodies without a drive motor, and Olympus Zuiko 50mm f/2.0 for Four Thirds and Micro Four Thirds bodies). To insure that the hair detail we use for making critical judgements about camera noise processing and detail rendering is in sharp focus at the relatively wide aperture we're shooting at, the focus target at the center of the scene is on a movable stand. This lets us compensate for front- or back-focus by different camera bodies, even those that lack micro-focus adjustments. This does mean, though, that the focus target itself may appear soft or slightly out of focus for bodies that front- or back-focused with the reference lens. If you click to view the full-size image for one of these shots and notice that the focus target is fuzzy, you don't need to email and tell us about it; we already know it. :-) The focus target position will simply have been adjusted to insure that the rest of the scene is focused properly.

Extremes: Sunlit, dynamic range and low light tests
Very high resolution with very good highlight and shadow detail. Very good low-light performance, capable of capturing bright images in near darkness.

+0.3 EV	+0.7 EV	+1.0 EV

Sunlight:
The Nikon D5100 handled the deliberately harsh lighting very well in the above test. Though contrast is a little high, highlight and especially shadow detail are very good. The camera's contrast adjustment also did a good job of decreasing overall contrast without producing strong color variations; see the section below. The +1.0 EV exposure did the best job here, as the model's face was still a bit too dim at +0.7 EV. A few highlights were blown in the model's shirt and bright flowers, though not as much as we're used to seeing, and good detail was preserved in the shadows with lower than average noise. Note that these shots were captured with the Nikon D5100's Active D-Lighting control set to its default of "Off." See below for how Active D-Lighting and contrast settings help with hot highlights and deep shadows.

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. In actual shooting conditions, be sure to use fill flash in situations like the one shown here; it's better to shoot in open shade whenever possible.)

Contrast Adjustment
We really like it when a camera gives us the ability to adjust contrast and saturation to our liking. It's even better when those adjustments cover a useful range, in steps small enough to allow for precise tweaks. Just as with its saturation adjustment, the Nikon D5100's contrast setting meets both challenges, the contrast steps actually being a little finer than those for saturation, and thus even more to our liking.

Minimum Contrast
Contrast set to lowest, +0.7 EV	Contrast set to lowest, 0 EV

At its lowest contrast setting, the D5100 did a really excellent job of preserving highlight detail, maintaining natural-looking skin tones, and bringing nice detail out of the shadows. Overall, excellent results here, especially when the contrast setting is tweaked. (This is a really tough shot; the Nikon D5100 does a better than average job handling it.)

Contrast Adjustment Examples
-3	-1	0	+1	+3

The series of shots above shows results with several different contrast adjustment settings, showing the minimum step size around the default, as well as both extremes. There is also an Auto setting available. While you can see the extremes, it's hard to really evaluate contrast on small thumbnails like these, click on any thumbnail to go to the full-size image.

One very nice feature of Nikon's contrast adjustment is that it has very little effect on color saturation. Contrast and saturation are actually fairly closely coupled, it's a good trick to be able to vary one with out the other changing as well. Nikon did a good job here.

Active D-Lighting
Active D-Lighting attempts to preserve detail in both highlights and shadows in high-contrast situations, while maintaining moderate levels of contrast. The series of shots below show the effect of the various Active D-Lighting settings available on the Nikon D5100 on our high-contrast "Sunlit" Portrait scene. Note that Active D-Lighting is different from the touch-up menu's D-Lighting, as it is performed during image capture instead of after. (It does affect only JPEG images though, Nikon very properly doesn't apply tonal adjustments like this to RAW file data. NEF files, however, are tagged so that Nikon software can automatically apply the effect when converted.)

"Sunlit" Portrait Active D-Lighting (0 EV)
	ADL Settings: Off (Default) Auto Low Normal High Extra High

Mouse over the links to see how the various levels of Active D-Lighting affects our "Sunlit" Portrait shot at default exposure. Click on a link to get to the full-res image. (Active D-Lighting's effect can be a little subtle in shots like those above, so we decided to use a mouse-over to better show how each setting compares to Off.)

When Active D-Lighting is enabled, the camera usually exposes for the highlights in an attempt to preserve them, then adjusts the tone curve to bring the midtones and shadows back up to produce an image that doesn't look underexposed. In this case, the default exposure without Active D-Lighting didn't have any blown highlights to preserve, so this is not the best example. To see how Active D-Lighting works with some positive exposure compensation (about +0.7 EV) with this shot, see the examples from our Nikon D7000 review below:

"Sunlit" Portrait Active D-Lighting (D7000, +0.7EV)
	ADL Settings: Off (Default) Auto Low Normal High Extra High

As you can see from the thumbnail images and histograms above, higher values of Nikon's Active D-Lighting do a very good job at preserving highlights while bringing up shadows and deeper midtones, without making the image look too flat. Normally, there is a noise penalty to be paid for boosting shadows, but noise levels in the shadows are very low with this sensor (on both the D7000 and D5100), so increased shadow noise is not much of a concern here.

See below for how Active D-Lighting worked on our Far-field House shot.

Far-field House Active D-Lighting (0 EV)
Off	Auto	Low
Normal	High	Extra High

Here are the results with our Far-field House shot. The D5100's Active D-Lighting worked better here, as the default exposure wasn't underexposed like it was for its "Sunlit" Portrait scene. As you can see, Active D-Lighting brought up shadow detail while holding on to more of the highlights. Also note the slight blue cast in the white trim of the house as the strength of Active D-Lighting is increased. The Auto setting did a pretty good job here.

New HDR Mode
The D5100 marks a first for Nikon by offering an in-camera high-dynamic-range imaging function, something we've seen in several DSLRs from competing manufacturers. When enabled, the D5100 captures two images with one push of the shutter button, one underexposed and one overexposed and combines them in-camera to produce a high-dynamic-range JPEG. (RAW format is not supported). We don't believe the Nikon D5100 performs any micro-alignment of the two images even though the user manual warns of possible cropping. If it is, it can only correct for very small amounts of camera movement between shots, and so Nikon recommends the use of a tripod. Obviously moving subjects should also be avoided.

"Sunlit" Portrait HDR (0 EV)
	HDR Settings: Off (Default) 1 EV S=Med 2 EV S=Med 3 EV S=Low 3 EV S=Med 3 EV S=High

The Nikon D5100 allows you to set the exposure differential between the two images from 1, 2 or 3 EV, and there is also an Auto setting where the camera decides. Nikon says exposure differential can be expanded up to 5 EV when HDR is combined with Active D-Lighting. There is also an option to adjust the amount of "smoothing" that is applied to the boundaries between the two images, with selections of Low, Medium and High. Mouse over the links above to see how various levels of HDR affects our "Sunlit" Portrait shot and click on a link to get to the full-res image. As you can see, the higher levels make quite a difference to the overall exposure by opening up shadow detail and toning-down highlights while at the same time reducing shadow noise, but lower levels of smoothing can lead to artificial looking shadows around bright objects or halos and glowing around dark ones. As mentioned in the Field Test, colors can also be adversely affected in HDR mode, such as a drop in saturation. Still, it's a useful feature for capturing static scenes with dynamic range that exceeds the sensor for those not willing to use manual HDR techniques (bracketing exposure and then combining images while post-processing).

Far-field House HDR (0 EV)
Off	1 EV, S=Med	2 EV, S=Med
3 EV, S=Low	3 EV, S=Med	3 EV, S=High

Here are the same HDR settings with our Far-field House shot. Again, some settings do a very good job of taming hot highlights while bringing up some of the shadows and deeper midtones, though notice the desaturation of colors, especially in the sky when using higher settings. You can also see ghosting in the tree branches and leaves from movement between the exposures caused by wind, as well the artificial-looking and uneven exposure when using the Low Smoothing setting.

Aperture Priority Mode 0 EV	Auto Exposure Mode 0 EV	Live View Face Priority AF 0 EV

Face Detection. Here, we can see the effects of the Nikon D5100's full Auto Exposure mode and face detection in Live View mode versus Aperture Priority mode. As you can see from the shots above, the Auto mode made only a modest improvement to exposure, though default contrast has also been toned down. But in Live View, Face-priority Autofocus mode made a huge difference, actually slightly overexposing the image.

Dynamic Range
A key parameter in a digital camera is its Dynamic Range, the range of brightness that can be faithfully recorded. At the upper end of the tonal scale, dynamic range is dictated by the point at which the RGB data "saturates" at values of 255, 255, 255. At the lower end of the tonal scale, dynamic range is determined by the point at which there ceases to be any useful difference between adjacent tonal steps. Note the use of the qualifier "useful" in there: While it's tempting to evaluate dynamic range as the maximum number of tonal steps that can be discerned at all, that measure of dynamic range has very little relevance to real-world photography. What we care about as photographers is how much detail we can pull out of the shadows before image noise becomes too objectionable. This, of course, is a very subjective matter, and will vary with the application and even the subject matter in question. (Noise will be much more visible in subjects with large areas of flat tints and subtle shading than it would in subjects with strong, highly contrasting surface texture.)

What makes most sense then, is to specify useful dynamic range in terms of the point at which image noise reaches some agreed-upon threshold. To this end, Imatest computes a number of different dynamic range measurements, based on a variety of image noise thresholds. The noise thresholds are specified in terms of f-stops of equivalent luminance variation in the final image file, and dynamic range is computed for noise thresholds of 1.0 (low image quality), 0.5 (medium image quality), 0.25 (medium-high image quality) and 0.1 (high image quality). For most photographers and most applications, the noise thresholds of 0.5 and 0.25 f-stops are probably the most relevant to the production of acceptable-quality finished images, but many noise-sensitive shooters will insist on the 0.1 f-stop limit for their most critical work. A full discussion of all the data Imatest produces is really beyond the scope of this review: Visit the Imatest website for details of what the program measures, how it performs its computations, and how to interpret its output.

JPEG. The graph at right (click for a larger version) was generated using Imatest's dynamic range analysis for an in-camera D5100 JPEG file with a nominally-exposed density step target (Stouffer 4110). At default settings and base ISO, the graph shows 10.2 f-stops of total dynamic range, with 7.74 f-stops at the "High" quality level. These are very good numbers. Compared to the Nikon D7000 which uses the same or very similar sensor, the D5100 scored slightly lower at the "High" quality level (7.74 vs 7.97 f-stops), though total dynamic range was slightly better (10.2 vs 10.0 f-stops). Note though that this measurement has a margin of error of about 1/3 f-stop, so differences of less than 0.33 can be ignored. Taking the margin of error into account, dynamic range performance was indeed very similar to the Nikon D7000, which is to say, very good.

RAW. The graph at right is from the same Stouffer 4110 stepchart image captured as a RAW (.NEF) file, processed with Adobe Camera Raw using the Auto setting, then tweaked manually. The Nikon D5100's RAW file scored 2.3 f-stops more in total dynamic range than the JPEG (12.5 vs 10.2 f-stops) and the score at the highest quality level increased 2.26 f-stops from 7.74 to 10 f-stops. This is an excellent score, among the best cameras we've tested to date. Again, results are very similar to those of the Nikon D7000, with nearly the same High Quality score (10.1 vs 10 f-stops) though the D5100 scored slightly higher in total dynamic range (12.5 vs 12.1 f-stops). It's worth noting here is that ACR's default noise reduction settings reduced overall noise somewhat (see the plot in the lower left-hand corner) relative to the levels in the in-camera JPEG, which would tend to boost the dynamic range numbers for the High Quality threshold. Also, the extreme highlight recovery being performed by ACR here would likely produce color errors in strong highlights of natural subjects.

	1 fc 11 lux	1/2 fc 5.5 lux	1/4 fc 2.7 lux	1/8 fc 1.3 lux	1/16 fc 0.67 lux	1/16fc No NR
ISO 100	2 s f2.8	4 s f2.8	8 s f2.8	15 s f2.8	30 s f2.8	30 s f2.8
ISO 200	1 s f2.8	2 s f2.8	4 s f2.8	8 s f2.8	15 s f2.8	15 s f2.8
ISO 400	0.5 s f2.8	1 s f2.8	2 s f2.8	4 s f2.8	8 s f2.8	8 s f2.8
ISO 800	1/4 s f2.8	0.5 s f2.8	1 s f2.8	2 s f2.8	4 s f2.8	4 s f2.8
ISO 1600	1/8 s f2.8	1/4 s f2.8	0.5 s f2.8	1 s f2.8	2 s f2.8	2 s f2.8
ISO 3200	1/15 s f2.8	1/8 s f2.8	1/4 s f2.8	0.5 s f2.8	1 s f2.8	1 s f2.8
ISO 6400	1/30 s f2.8	1/15 s f2.8	1/8 s f2.8	1/4 s f2.8	0.5 s f2.8	0.5 s f2.8
ISO 12800	1/60 s f2.8	1/30 s f2.8	1/15 s f2.8	1/8 s f2.8	1/4 s f2.8	1/4 s f2.8
ISO 25600	1/125 s f2.8	1/60 s f2.8	1/30 s f2.8	1/15 s f2.8	1/8 s f2.8	1/8 s f2.8

Low Light. The Nikon D5100 performed well here, able to capture usable images down to the 1/16 foot-candle light level (about 1/16 as bright as average city street lighting at night), at all ISO settings. As is often the case, the D5100's metering system struggled a bit with getting the exposure right at the lowest levels though, so we used manual exposure for these shots. Color balance with auto white balance was fairly neutral at higher light levels, but took on an increasingly strong blue or magenta cast as light levels dropped. Noise was quite low up to ISO 1,600, and even a higher ISOs there's still a lot of detail to work with when high ISO NR is set to "Off" (which still applies some noise filtering at ISOs over 1,600). The Nikon D5100 gives you four options for high ISO noise reduction: Off, Low, Normal, and High, so you have some flexibility in deciding how much noise to trade for detail. Except for the "No NR" shots in the table above, these were all shot using the Normal NR setting, and Long Exposure NR was enabled so it was applied to exposures longer than one second. There are a number of hot pixels visible at higher ISOs (ISO 800+) and also at lower ISOs when Long Exposure NR is turned off, but that's not unusual. We did not detect any significant banding issues.

The camera's phase-detection autofocus system was able to focus on the subject down to between 1/8 and 1/16 foot-candle light level unassisted with the kit lens at 18mm and f/3.5. That's pretty good for a relatively slow kit lens. The Nikon D5100 was able to autofocus in complete darkness with the AF assist enabled. In Live View mode, the camera's contrast-detect autofocus was only able to focus down to just below 1/4 foot-candle and AF assist is not supported in Live View mode.

(Keep in mind that the longer shutter speeds here demand the use of a tripod to prevent any blurring from camera movement. A useful trick is to just prop the camera on a convenient surface, and use its self-timer to release the shutter. This avoids any jiggling from your finger pressing the shutter button, and can work quite well when you don't have a tripod handy.)

How bright is this? The one foot-candle light level that this test begins at roughly corresponds to the brightness of typical city street-lighting at night. Cameras performing well at that level should be able to snap good-looking photos of street-lit scenes.

NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim lighting. (For example, a child's ballet recital or a holiday pageant in a gymnasium.) Digital SLRs like the Nikon D5100 do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects.

Print Quality
Makes excellent 24 x 36 inch prints from ISO 100-400; ISO 3,200 shots still have great detail at 11 x 14; ISO 12,800 shots make a good 4 x 6.

ISO 100 images make excellent 24 x 36 inch prints with great detail and color. This is true at ISO 200 and 400 as well. Good wall display prints are possible up to 30 x 40 inches.

ISO 800 shots look good at 16 x 20, with very slight luminance noise in the shadows, but not bad at all.

ISO 1,600 prints look quite good at 13 x 19 inches.

ISO 3,200 makes a nice 11 x 14, with minor apparent noise in some shadowy areas.

ISO 6,400 shots are pretty good at 8 x 10, better than usable. There's a little luminance noise in the shadows, but overall it's a good performance.

ISO 12,800 prints a respectable 4 x 6.

ISO 25,600 images are too muted and noisy to be called good.

Overall a very impressive performance from the Nikon D5100, on par with the Nikon D7000 to a large extent.

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 Pro9000 Mark II studio printer, and on the Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)