|Left: Nikon D610 Right: Nikon D7100|
Now that the D600 has been updated to the D610, the question of which 24mp Nikon DSLR to get comes up again: the D610 or the D7100. With these two cameras we have one of the most level playing fields in comparing FX and DX. Both have 24mp, both with near identical control layouts. These are essentially the same camera with different sensors... that's it. This is about as equal a playing field as possible between full frame and crop sensors. The real question, of course, is not about debating the merits of these two. When most people ask this question, what they are really asking is: is there a way to justify the full frame camera, which costs nearly double the price. As they say, bigger is always better... until it isn't.
Updated April 2014. New ISO samples and various additions.
Lenses, Diffraction Limitation and Moiré
All to often, photographers only focus on the noise and dynamic range aspects of full frame cameras versus crop, but the differences in optical systems have just as important influences on shooting experience and image quality.
Diffraction and Perceived Lens Sharpness
Whatever advantages that the D7100 has in removing the low-pass filter are mitigated by the high pixel density of the sensor and the demands this places on the quality of the lenses being used. Even though full frame lenses are cheaper than DX lenses, the larger pixels of the D600 place "less of a burden" on the quality of the glass. T
An Overlooked FX Advantage
Another advantage of the FX over DX is that for the equivalent depth of field, the FX camera will be using a lens one stop down. At close range, this is an advantage that is often over-looked. Imagine going for a trendy super-shallow depth of field shot with the D7100 and a 50mm f/1.4 lens. Wide open, fast primes have all sorts of optical flaws, though some would use the more flattery term "dreaminess" rather than "flawed." For the equivalent D610 image, an 85mm (because a 75mm doesn't exist) lens shot at f/2 would give the equivalent depth of field. The D610 image would be superior because stopped down, the FX lens would be operating in a more optimal portion of it's aperture range, meaning that even though both lenses would give similar looking out of focus backgrounds, the D610 and FX lens would be more contrasty and would suffer less from chromatic and spherical aberrations.
This is the big DX advantage, further magnified by the better 51-point autofocus system in the D7100. The 70-300VR is a popular lens for both DX and FX, and gives good optical results up to the 200mm mark on both systems. However, of DX, the lens fully extended gives you the equivalent of 450mm, something that you can't achieve on FX without buying a more expensive lens. When you combine the better AF system and further reach of the DX D7100, you have a camera that is better suited for sports, like soccer and baseball. However, the D610 would be capable of achieving higher shutter speeds because of its extra stop of ISO power.
It bears repeating that there is no inexpensive way to achieve 400mm on either DX or FX. Even "inexpensive" lens options cost over $1000 USD.
Buffer capacity is the most glaring shortcoming of the D7100. Though it is rated at 6fps, the buffer will fill after only 6 shots in NEF mode. However 12 shots are possible in JPEG FINE mode before the buffer fills. In comparison, the D610 can shoot approximately 14 NEF images before its buffer fills, or roughly 30 images in JPEG FINE. The D7100's small buffer size is an especially aggravating issue for bird photographers; if you are interested in this area of photography, its recommended to use the fastest SD card that you can get a hold of so that the camera is still (somewhat) usable during an extended burst after the buffer is full.
ISO/Safe Hand Holding Ability
With the D7100 for non-professional usage, ISO 3200 is about as high as you would want to take it for quality results. ISO 6400 would be the equivalent limit with the D610, which is in keeping with the 2.3x increase in sensor surface area. Under equivalent circumstances, you would get one additional stop in terms of safe hand holding speed. However, one additional stop is not the advantage that it used to be. In the D3/D300 generation, ISO 1600 was as high as you would want to take DX, and ISO 3200 for FX. As the ISO ranges of cameras increase, the additional stop of light gathering power becomes less significant. Here are high(er) ISO samples (pop refrigerators) for the two cameras, normalized for field of view and depth of field. Images are out of camera JPEG (L).
- D7100 with 18-140mm, 24mm, f/5.6
- D610 with 24-85mm, 35mm, f/8
Click on the following images to view at 100% crop size:
With the current set of cameras, assuming viewing angles close to "normal" human vision (however you define it), you can safely handhold the D7100 at maximum ISO and aperture in an indoor room. The extra stop that D610 gives you means that you can safely handhold if the room is dimly lit. The take-home message is this: the advantage that the full frame D610 gives over the D7100 depends on what lens set that you are using. If you are already using a f/2.8 fast zoom with DX, then a move to the D610 would be less of an improvement than if you were using DX with a variable aperture kit-zoom. However, when shooting conditions become dim, you will still produce sharper results by using the built-in fill-flash.
However, there's a subjective difference that isn't as easily conveyed by objective tests. Shooting with a D610 tends to produce more "3-dimensional images" due to the shallower depth of field, the greater apparent acuity coming from the full frame lenses and the higher dynamic range of the sensor.
There is not much of a meaningful difference between these two cameras. If you go for the D610, you get the extra 'dreamy' bokeh from having a larger sensor, but if you were serious about full-frame videography, you would have likely gravitated to Canon because of the larger videographer following in that community. Even though Canon's are regarded as the go-to cinematography DSLR's, on a video quality basis alone, all modern Nikon's are extremely competent in this field, and easily the equal of their Canon counterparts.
Having endured a year of troubles with the D600 debris issue, Nikon hopefully will have turned a corner with the D610. Truth be told, almost all of the recent launches seem to have had some quality issues, though the D7100 appears to be relatively trouble free at the moment. A bit of oil splatter on a new camera is not unheard of, but the problem with the D600 was that oil and debris accumulated with continued usage. As much of an annoyance this can be, especially when you are spending $1000 or even $2000 for a camera, the bright spot is that Nikon did finally issue a broad based service advisory for all D600 cameras. For Nikon, their communication has been a much bigger sin than their servicing.
Value for Money
This one's not a contest. The D7100 gives much more bang for the buck than the D610. Both cameras can do most things on a relatively equal footing. The D610 does what traditional full frame cameras do well: creating quality images that have a smooth tonal transitions. There is no question that the D610 will produce higher quality and more pleasing images, but you have to have the ability to bring it out of the camera if you want to produce images that stand out from the DX crowd. Think of all of those "what camera did this come from" threads that you see on DPReview... The D7100 is a more versatile camera, though, and its high speed crop mode and more advanced autofocus system alone make it a more intriguing choice.
That said, both models represent Nikon well at their respective price brackets, and offer photographic capability that was dreamt of at these prices not just a few years ago. However.... in certain circumstances, a full frame system can be less expensive than a DX system, depending on the incentives that are in place. This was certainly the case for the D600 in the Christmas season after its launch. However, the market conditions at the end of 2012/beginning of 2013 aren't likely to be seen again, and all things being equal, a FX system will for most people, be more expensive in the long run than the equivalent DX system.
Choosing between the D7100 and D610 is likely a decision about wants rather than needs. The D7100 is an extremely competent camera; the D610 more so. If it were truly an issue of need, the camera in consideration would not be the consumer-oriented D610, but rather, the (mostly) professional quality D800 instead. The great thing about the D7100 and the D610 is that they are basically the same camera with different sensors. Compare that to the Canon pairing of the EOS 70D and the 6D; even though the 6D gains in image quality with it's full frame sensor, it looses out in autofocus ability against the 70D. Nikon thankfully hasn't forced the consumer into that dichotomy; except for pixel density, a photographer will for the most part have a superior shooting experience with the D610 compared to the D7100. So it always comes back to whether or not the performance increase justifies the cost....