Shadow noise

Nikon's DSLRs have gained a well-deserved reputation for outstanding noise performance. And with 24MP now becoming common among enthusiast DSLRs, we thought it would be interesting to see how the D7100 performs against both a full frame and APS-C rival. In the comparison below we've drastically opened up the shadows using Adobe Camera Raw 7.4 with sharpening and noise reduction turned off, to shine a light on the sensors' inherent capabilities. We've compared the D7100 with two 24MP rivals, the APS-C Sony SLT-A77 and the full frame Nikon D600. All three cameras were shot at ISO 100.

Nikon D7100 - ACR +3.0EV 100% crop
Nikon D600 - ACR +3.0EV 100% crop
Sony SLT-A77 - ACR +3.0EV 100% crop

As you can see, the D7100 keeps chroma noise impressively well under control. As expected, its output is not quite as clean as that of the larger sensor D600. But the D7100 does not suffer by much in terms of retaining detail in the spools of thread. See the high ISO comparison page of this review for a low light comparison of the D7100 and D600. The D7100 provides noticeably cleaner results and more visible detail than the Sony SLT-A77.

Real world sample

While the results of our studio scene reveal interesting information about the sensor's maximum capabilities, it's important to place those results in the context of real-world photography. Below is an image shot outdoors at ISO 100. The high contrast in this scene required an exposure compensation adjustment of -2.3 EV below the camera's matrix metering in order to hold detail in the sky. We've taken the same file .NEF raw file and converted it in ACR 7.4 three times - once at ACR's default exposure settings, and twice more with the Basic Panel adjustments detailed below. Noise reduction was disabled in all three examples. This example was shot with the 18-105mm kit lens.

ACR default settings with NR off 100% crop
ACR with Exposure +.60, Highlights -30, Shadows +30 and Blacks +60 with NR Off 100% crop
ACR with Exposure +1.00 Highlights -70, Shadows +95, Blacks +60 and Clarity +50 with NR Off 100% crop

Looking at these examples, it's obvious that by exposing for the highlights, the default conversion blocks significant shadow detail. In the second conversion we were able to boost exposure and open the shadows substantially with no meaningful noise penalty and maintain a pleasing compromise between image contrast and shadow detail. In the third attempt we purposefully made an extreme adjustment to open the shadows as much as possible. Despite such an aggressive move, you only see a marginal amount of chrome noise, even with ACR's NR slider set to 0. While this HDR-like result may not be to everyone's taste, the point here is that at base ISO, the D7100 provides enough headroom in shadow detail to create this effect from a single exposure.

In short, the D7100's raw file shows an impressive ability to withstand luminance boosts in the shadows, revealing usable detail while keeping noise at very low levels. We've seen this in other current generation Nikon DSLRs like the D600 and D800 and it represents a significant improvement in sensor performance compared to older cameras like the D300S and D90.

Overall image quality

The D7100's image quality is very impressive across its standard ISO sensitivity span of 100-6400. From an image detail standpoint, there is precious little separating the D7100 from the lower-spec'd D5200, though this really speaks to just how good the latter is rather than being a criticism of the former. At high ISO sensitivities the D7100 does a good job of retaining fine detail while minimizing chroma and luminance noise, falling just a bit shy in this regard to the larger sensor full frame D600. And after a few weeks of real-world shooting with the camera we've not found the D7100's lack of an OLPF to produce moiré to any meaningfully greater degree than its APS-C rivals which do use a filter.

As we've come to expect from Nikon DSLRs, the default JPEG settings of the D7100 produce files that lean more towards a more natural, 'unprocessed' look, avoiding sharpening-induced edge halos and overly aggressive smearing at high ISOs. This means that at high ISO settings, JPEGs tend to be gritty - compared to those from Canon and Sony, for example - but relatively detailed. The camera's raw files deliver excellent detail and can tolerate a fair degree of low-radius sharpening for crisp-looking results without prominent edge halos. Chroma noise is also kept well under control - though not at the level of the D600 - throughout high ISO settings.

The D7100's Auto white balance setting is consistently accurate. And if the images look a little too neutral for your taste, the Auto2 setting can be used to give a slightly warmer result. As we demonstrated in our Nikon D800 review, Nikon's matrix metering can be biased according the brightness of the object on which it locks focus. While this makes sense, as most times you do want to give priority to the subject on which you're focusing, it is something to be aware of when shooting high-contrast scenes.

Even taking AF point bias into account though, in real-world shooting we regularly found ourselves boosting exposure compensation by about 0.3 EV above the matrix metering setting for more pleasing results when shooting indoor scenes of moderate contrast. We don't want to make too much of this, as a conservative approach to metering is preferable to clipping data and the D7100 does a very good job of protecting highlight information.

Nikon has chosen well-considered default JPEG settings but if you're interested in tweaking these to taste, the D7100 offers a comprehensive range of color, contrast and sharpening settings that can be adjusted with a minimum of fuss. For the greatest degree of editing flexibility, however, you'll want to edit the raw files of course, which can withstand more extreme exposure edits like the ones we've demonstrated here.