Wednesday, August 5, 2015

Nikon D750 vs Sony A7 Mark II

Left: Nikon D750     Right: Sony A7 Mark II

The Nikon D750 and Sony A7 Mark II  are the zeitgeist of the 2015.... at least as far as the camera manufacturers would prefer. Nikon and Canon have been trying to move their enthusiast shooters upmarket as far as possible, and for Nikon, that means switching users from APS-C to full frame. Sony, even if they aren't being accused of it, is also doing the same thing, as there as been a marked proliferation of full frame FE-mount lenses in 2014-2015 at a time when their traditional APS-C E-mount lens range has remained stagnant. In other words, these two cameras are representative of how the camera companies are trying to shape the camera market.

For all of the little stumbles (shaded flare issue and one firmware update) that the D750 has gone through, it is probably the best refined concept of what a DSLR could be at the moment.... capable, full featured and most importantly in this day and age, smaller and lighter than what came before. It's not perfect, but it is pretty much excellent at the core of what it is.

The Sony A7 Mark II is a more ambitious device, and arguably representative of what the future of cameras will be. It is an improvement over the first A7, a good camera that had more than a few Version 1.0 traits, but compared to the many, many times that Nikon has iterated their serious DSLR range, the Sony is still the new comer on the black. Smaller body, built in image stabilization, on-chip phase detection during live view. All of these are useful and crowd pleasing, but do they add up against the tried-and-true DSLR form factor?

General Usage Considerations

The Nikon D750 is a full frame device with the soul of a crop frame camera. Except for the taller viewfinder prism, the D750 is more or less the same size as the APS-C D300... but volume-wise it is smaller and lighter.If you prefer to shoot with primes, the overall package is fairly un-burdensome for a full frame camera.

Nikon D750 with AF-S 50mm f/1.4G

Paired with pro-zoom lenses, the proposition changes. All of the 24-70mm f/2.8 zoom lenses are bulky, and though not as heavy as when paired with the D810, the D750 reverts back to the feeling of "large and bulky" when paired with these lenses. If you are using the Nikon f/2.8 trinity (14-24, 24-70, 70-200), those lenses tend to balance better on the D810 anyway, as they feel somewhat front heavy on the light D750 body.

The Sony A7 Mark II, though smaller than a DSLR, is also not a light weight device. Volume and weight went up from the transition from the first A7. Most will find the second version easier to hold because of the larger grip, but the button placement isn't as ergonomic as on the Nikon, and neither is the tactile feel of the command dials. To its benefit, it is an extremely versatile system for adapting third-party lenses and for videography. The D750 is the "video" DSLR for Nikon, the A7 cameras have the added benefit of focus peaking (...we're waiting, Nikon...), image stabilization and the fact the smaller overall size makes them easier to fit with things like video cages and slider dolly's.

Sony A7 Mark II with FE 55mm f/1.8

Like that other famous "small" full-frame system, the Leica M, the Sony A7 Mark II is a wonderful camera to build a prime lens system off of... particularly with the superb Batis lenses. However, the Sony's size advantage becomes blunted when you switch to longer/faster lenses. The system is still smaller and lighter, but mostly by virtue of being composed of primes and f/4 zooms. Your messenger bags or roller cases might be smaller, but you will need them nonetheless.

Nikon D750 with AF-S 70-200mm f/2.8       Sony A7 Mark II with FE 70-200mm f/4

One area where the Sony E/FE-mount system falls short is in its reliance on the (widely-available) NP-FW50 battery, which lags behind in capacity with the batteries used in the advanced Nikon and Canon cameras. Sony addresses this with the A7s and A7r Mark II cameras by supplying a second battery, but the fundamental problem is that the battery pack is too small. This is the same issue that Leica users faced with the M9; when the M240 succeeded it, the battery pack grew approximately twice in size.

Top: Sony NP-FW50  Bottom Nikon En-El15

For practical purposes, the A7 Mark II has less than half the battery life of of the D750. This is more than enough for a days worth of casual shooting or for a short client session. It becomes more of an issue if you are doing a full days wedding shoot, or if you are prone to leaving the LCD screen on for extended periods of time. Sony really ought to be commended for keeping their battery lineup simple, one smaller size for the RX100 cameras and the NP-FW50 for everything about it, but they really need a pro-spec battery for their next generation of cameras.

Image Quality

The following is an ad hoc demonstration of the camera's JPEG output quality through the ISO range. Pay attention to the legibility of the soda bottles for detail retention (or lack thereof) as the ISO value rises, speckling in the broad colour patches for overall image noise, as well as the harshness of the reflections and shadows as dynamic range decreases. These samples are not directly comparable to similar samples found elsewhere in this blog because of variable ambient lighting conditions. Naturally, there is more processing leeway in the original RAW files, but comparing RAW files from different cameras can give one a false sense of fairness. Because each RAW format is different, the best and most representative results depend on each file being processed for best results. Often, different RAW files are compared at default converter settings, which is a bit like comparing default JPEG settings. Hence, for quick comparative purposes we are using the JPEG files out of the camera, as they can give insight into how the competing imaging engineers view the output of their respective cameras.

These are shot at the same settings (24-70mm lenses, NR turned off, dynamic range optimization off, default sharpening) Because they are both Sony-sourced sensors, you would expect similar results, and that is what we see... with some exceptions.  Click on images for 100% crop view.

ISO 100

At base ISO, there isn't much to differentiate except for the different renditions that the cameras JPEG engines use. The Sony has more default sharpening (no surprise, since Nikon uses the lowest default settings of any manufacturer), but both cameras are recording roughly the same levels of detail. 

ISO 12800

At higher ISO, the Nikon JPEG engine does a much better job of preserving detail and keeping chroma noise in check. The EXPEED 4 generation of cameras have some of the best JPEG renderings on the market, as the output is comparable to the previous EXPEED 3 files processed in RAW at higher quality settings.

One of the downsides of all Sony cameras is that even with noise reduction turned "off" it is never truly off. There is a fair amount of detail smearing; the pattern of the noise reduction is the  the same across almost all of the Sony cameras. At the edge of usability, the pattern of the noise reduction looks the same, whether it be a RX100, an A6000 or an A7 camera body. All of this is moot if you use RAW, but the Nikon has an advantage there as well, as the Nikon RAW format can be set at 14-bit uncompressed, whereas the Sony format is fixed at an 11-bit compressed scheme. If you have a light hand during post processing, there won't be much of a meaningful distinction, but if you bend the files aggressively, the Nikon will have better data integrity.

In other words, even with similar sensors, you can get different outputs because of the choices and priorities that the respective engineering departments choose. For example, the following is a 100% crop of an ISO 100 sample taken at 1/4000s with the body cap on. In other words, only the read noise is recorded in this instance, the electrical interference caused by the physical act of pulling the data off of the sensor. The bottom half of the sample has been pushed 8EV to accentuate the noise pattern.

Read noise: ISO 100, 1/4000s

As you can see, the D750 records some of the read noise whereas the Sony A7 Mark II does not. The Sony is how Nikon cameras used to behave (up until the D5300/ EXPEED 3 generation) ; read-nosie reduction by clipping the black point. The practical implication is that the Sony is probably not a good candidate for astro-photographers who need to do deep-sky imaging (nebulas and galaxies.)  The aggressive clipping of the black point mutes the ability of the camera to record photos for faint sources, otherwise for all other night-time photo uses, the Sony is fine.

Here is a 30s image patch at ISO 6400 with the cap on; this lets more of the thermal/dark current noise to be recorded into the image. This is the noise that is inherent in the cameras circuity.  

Dark Current Noise

It's a similar pattern, but the Sony's noise profile is a bit more course than with the Nikon. This isn't surprising, as there is more circuitry on the the A7 Mark II sensor (phase detection elements and the surrounding image stabilization apparatus) than there is on the D750 chip.

So, differences aside, this isn't a particularly new trend, as Nikon's software engineers have generally done well to get (possibly) the best results out of Sony-sourced image sensors. In fact, it's instructive to compare a Nikon APS-C camera to a Sony full-frame camera in order to see how much a difference in-camera JPEG optimization can make.

Concluding Thoughts

One of these products is conceptually a better concept than the other, and one of them is just plain a better camera. Regardless, the one that is specifically better for you will depend on your shooting needs. If the Sony A7 Mark II is the camera of the future, it also doesn't meet all of the needs of every shooter at present. For all of Nikon's mistakes (big and little) since 2011, the D750 is one of the very best of its breed. If only there was one way to combine the best qualities of both cameras....

With thanks to Broadway Camera

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