The pop-up flash on the D600 has the same specs as its counterpart on the D800 with a guide number of 12m at ISO 100. Flash exposure compensation can be set from -3 EV to +1 EV.
As on the D800, you can also use the D600's built-in flash to wirelessly trigger up to two groups of Nikon Speedlite flash units. Last-generation flashes like the two SB-800s pictured here can be picked up cheaply on the used market, and make great slaves for tabletop macros or outdoor portraits.

Shadow noise

Nikon's DSLRs have gained a well-earned reputation for outstanding noise performance. In the comparison below we've drastically opened up the shadows using Adobe Camera Raw (a beta version of 7.3) with sharpening and noise reduction turned off, to shine a light on the sensors' inherent capabilities. We've compared the D600 with two full frame rivals, the 24MP Sony SLT-A99 and the 22MP Canon EOS 5D Mark III. All three cameras were shot at ISO 100.

Nikon D600 - ACR +3.0EV 100% crop
Canon EOS 5D Mark III - ACR +3.0EV 100% crop
Sony SLT-A99 - ACR +3.0EV 100% crop

As you can see, the D600 and the Sony SLT-A99 perform similarly, with the former showing a bit less chroma noise in the shadows and greater detail in the spools of thread. The Canon EOS 5D Mark III is displaying noticeably more prominent chroma noise than either the Nikon or Sony models.

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 under daylight conditions at ISO 100. We've taken the same file, converted from a .NEF raw file and converted it in ACR 7.3 beta three times - once at ACR's default exposure settings, and twice more with the Basic Panel adjustments detailed below.

ACR default settings with NR off 100% crop
ACR with Exposure +.45, Highlights -50, Shadows +70, Whites -20 and Blacks -10 with NR Off 100% crop
ACR with Exposure +1.10, Highlights -60, Shadows +70, Whites -40 and Blacks +30 with NR Off 100% crop

As you can see, the default conversion blocks some shadow details. In the second conversion we were able to boost exposure and open the shadows with very little noise penalty and still maintain a pleasing overall exposure. In the third attempt we purposefully made an extreme adjustment to open the shadows as much as possible. Obviously this veers towards a more surreal HDR-like overall exposure. Yet if you did need to pull this much information out of the shadows, in creating a multi-image composite for example, it's important to know that this much data exists within a single exposure in the D600.

In short, the D600's raw file shows an impressive ability to withstand luminance boosts in the shadows, revealing usable detail while keeping noise at very low levels. This is one of the biggest strengths of Nikon's current-generation CMOS sensors compared to older cameras like the D300S and D90.

Overall image quality

The D600's image quality is very impressive throughout its standard ISO sensitivity span of 100-6400. Critically, files from the D600 are hard to tell apart from images captured from the 36MP D800, when they are examined at 100%. At high ISO sensitivities the D600 does a good job of retaining fine detail while minimizing chroma and luminance noise.

As we've come to expect from Nikon DSLRs, the default JPEG settings of the D600 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, but relatively detailed. The camera's matrix metering mode delivers well-exposed images in a variety of lighting scenarios and the auto white balance setting is consistently accurate. If AWB gives you images that look a little too neutral, the Auto2 setting is on hand to give a little warmth back.

While the D600's default parameters offer a reasonable starting point, discerning users will want to tweak the D600's JPEG output to taste. And if you're interested in that sort of thing, the D600 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 which can withstand more extreme exposure edits like the ones we've demonstrated here.