D500 vs D750: Pros and cons
Nikon’s full-frame DSLRs cost a lot more than its DX models. For almost the same price as the relatively basic FX-format D750, you can get the high-spec, high-performance DX-format D500. So how do you choose? We explain the pros and cons of these two models to help you decide when one you should choose.
- You get much more camera for your money – the D500’s specs easily outstrip the D750’s
- DX lenses are smaller, cheaper and lighter to carry around – and you can use FX lenses on DX Nikons too
- The 1.5x ‘crop factor’ makes telephoto lenses effectively 1.5x more powerful
- The smaller DX sensor can’t quite match a full-frame FX sensor for all-round image quality
- The smaller sensor leads to increased depth of field, which can be useful, but can also make beautiful bokeh harder to achieve
- At shorter focal lengths you’ll need to invest in DX lenses, which will be of little use if you upgrade to a full-frame Nikon later
- The larger sensor area opens the way for higher ISO sensitivities or higher resolution sensors that don’t sacrifice overall quality
- Depth of field is shallower, giving images more spatial depth and attractive background blur
- If you want to turn pro, a full-frame Nikon is best both for quality and pro accessories
- Even an ‘affordable’ FX-format Nikon like the D750 is a pretty expensive purchase
- You’ll need to invest heavily in lenses to exploit the quality potential of the full-frame format
- FX cameras are mostly (not always) bigger and heavier, and not designed for novices or those still learning
1. APS-C vs full-frame
Nikon makes digital SLRs in two formats. The smaller, cheaper DX-format cameras use sensors about the same size as old APS-C film, measuring around 24x16mm (half the size of the full-frame sensors in Nikon’s higher-end FX-format cameras). Technically, this reduces the image quality, but the bar is now set pretty high and it’s possible for DX-format cameras like the D500 to produce super-sharp billboard-size images that only an expert could tell from their FX-shot equivalents.
Nikon’s FX cameras have larger sensors the same size as the old 35mm film negative, measuring around 36x24mm. This gives them twice the area of the DX sensor, and increases the potential image quality as a result. The larger sensor pushes up the price, however, and it also requires larger, more expensive lenses. Almost all professional Nikon DSLR users choose FX cameras over DX models, though, so if you intend making money from your hobby, the pressure to move up to the larger format is strong.
2. Pixel density, noise and megapixels
Megapixels are not the only factor in image quality; the size of the pixels (or ‘photosites’) also matters. Bigger photosites mean less noise and better dynamic range; smaller photosites mean more noise and less dynamic range. So because the DX-format sensor in the D500 is smaller than that in the D750, there’s a limit to how many megapixels Nikon can cram in before these other aspects of image quality start to suffer. Nikon has used 24MP DX sensors, but it clearly feels 20 megapixels gives the ideal combination of resolution and overall image quality in the D500.
The larger sensor area of the FX-format D750 means that although it has only slightly more resolution than the D500 (24 megapixels versus 20.9 megapixels), there’s space on the sensor for much larger photosites and hence the potential for lower noise and better dynamic range.
Alternatively, the larger sensor area can be used to offer much higher resolution with the same photosite sizes – so you get sharper photos with no penalty in noise or dynamic range. The D810 is a good example of an FX-format Nikon that exploits the full-frame resolution advantage.
D500 vs D750: Depth of field
3. Depth of field
The size of a camera’s sensor has a big impact on the depth of field in your photos: the smaller the sensor, the greater the depth of field at a given lens aperture and equivalent focal length. This is a good thing if you’re photographing landscapes, still lifes, macro shots or any other kind of photography where you want as much depth of field as possible. It’s not so good if you want to make your subject stand out by blurring the background.
As a rule of thumb, DX cameras will effectively give you one f-stop more depth of field than FX ones at a given aperture, assuming you’re using an equivalent focal length to allow for the sensor’s ‘crop factor’ and to get the same angle of view.
The larger sensor in FX-format Nikons like the D750 means that you need to use longer focal length lenses to get the same angle of view, and this produces shallower depth of field. In the days of film, when focusing was relatively primitive and photographers relied heavily on ‘zone focusing’, extra depth of field would have been a bonus.
However, with today’s super-sharp lenses and pin-point focusing, photographers can properly exploit their cameras’ shallow depth of field effects, creative background blur and beautiful ‘bokeh’ – and FX Nikons can do this better than DX models.
The differences are subtle. In our sample shots, you have to look quite closely to see that the background in the picture from the D750 is more blurred.
The important thing to remember is that depth of field is not an ‘on-off’ thing. Sharpness falls away progressively, not all at once. The difference between the D500 and D750 is not the difference between sharp and blurred, but degrees of blur. After a while, though, you do start to notice that this tends to give full-frame shots a bit more spatial ‘depth’.
4. Lenses, sensors and image circles
All lenses need to produce an image circle large enough to cover the sensor area. Nikon’s DX sensor is smaller than its FX sensor, so it’s possible to make smaller, cheaper and lighter lenses specifically for this format. The drawback is that these lenses are little use on FX-format Nikons (except in Nikon’s lower-resolution ‘crop’ mode). Sometimes, though, a DX-format lens is the only option for owners of DX cameras because although you can use FX-format lenses too, their longer focal lengths usually rule them out for everyday and wider-angle photography.
The larger area of the FX-format sensor in the D750 means that you need lenses with a larger image circle to cover it – in other words, full-frame or FX-format lenses. You can physically mount smaller DX lenses on these cameras, but they must switch to a ‘crop’ mode that uses a smaller area of the sensor with half as many pixels (actually, rather fewer than half), so this is an emergency measure rather than something you’d want to do every day. The larger image circle easily covers DX sensors too, of course, so you can use FX lenses on DX cameras as well.
DX super-wide zooms: Smaller choice
If you want a super-wide-angle lens for a DX-format Nikon like the D500, you’ve no choice – you have to get a DX-format lens, typically a 10-24mm zoom, and almost all are variable-aperture ‘consumer’ lenses.
DX standard Zooms: More for amateurs
Again, the only way to get a useful range of focal lengths in a standard zoom for a DX-format Nikon is with a DX-only lens, typically in the range 18-55mm or 18-105mm. There are some constant-aperture lenses, but the only Nikon one is the old and expensive non-VR 17-55mm f/2.8.
Telephotos: DX has an advantage
With telephotos, though, an FX-format lens makes sense, even on a DX camera. The effective focal length increase is a benefit rather than a drawback, so Nikon’s 70-200mm f/2.8 becomes a 105-300mm f/2.8 equivalent – and you can still use it if you switch to an FX-format Nikon later.
FX Super-wide zooms: Better choices
On an FX-format Nikon you need super-wide-angle lenses designed for the bigger sensor size. These weigh more and cost more than their DX equivalents but they are better lenses, including the spectacular Nikon 14-24mm f/2.8 and the VR-equipped 16-35mm f/4.
FX Standard zooms: Better for pros
The standard, or ‘kit’ lens on a DX-format Nikon will typically offer a wider zoom range but a variable maximum aperture. If you want a constant-aperture lens, the FX format offers more choice – Nikon makes an older 24-70mm f/2.8 and a newer VR version.
Telephotos: Good but expensive
This is one lens type that works just as well on both FX-format Nikons like the D750 and DX models like the D500. The difference is that the crop factor of the smaller DX sensor gives lenses an effective 1.5x magnification, so here’s one instance where the DX format offers a bonus.
D500 vs D750: Autofocus
5. Size, weight and cost
This is where you might expect Nikon’s DX cameras to have an advantage, and they do at the beginners’ end of the market. But once you start looking at more advanced models the differences quickly disappear. Indeed, the D500’s body is slightly larger than the D750’s, not smaller. It’s true that DX lenses are generally smaller than their FX counterparts and less expensive, but that’s partly because there is a dearth of pro-quality constant-aperture zooms at shorter focal lengths for the DX format. Variable-aperture lenses are lighter and cheaper partly due to their lower spec.
You might assume that an FX-format Nikon system would be bigger, heavier and more expensive, but there’s more going on than just an increase in size. In fact, the range of lenses available for the DX and FX formats is not directly equivalent. Direct lens comparisons are difficult because most DX-format lenses are designed for cost-conscious consumers, while most FX-format lenses are designed for quality-conscious pros. Our tables compare like-for-like lenses as closely as we can get them, but there are important differences in the three key lens areas we’ve chosen. What it boils down to is that DX gives you the value, but FX gives you the choice.
Interestingly, Nikon DX and FX cameras use the same basic autofocus sensor modules, with only small modifications for the different formats. This means that autofocus advances happen across both formats – the D500 has essentially the same brand-new state-of-the-art autofocus system as the flagship Nikon D5.
But there is a further bonus for DX Nikon users: because the sensor area is smaller, the area covered by the autofocus sensor stretches right to the edge of the frame. For sports/action photography, the D500 comes out a clear winner partly because of its autofocus system.
The D750 uses Nikon’s older and less sophisticated 51-point autofocus system. It’s still very fast and powerful, even today, but not in the same league as the D500’s new 20K AF module. The key difference is not just the number of autofocus points, however, but their distribution.
The D750 has a larger sensor area, with the result that the autofocus sensor area does not reach right to the edges of the frame. It’s not necessarily an issue for general photography, since most shots are composed with the main subject near the centre of the frame, but it could prove an issue with erratic, fast-moving subjects.
D500 AF system:
- Multi-CAM 20K autofocus sensor module
- 153 AF points, including 99 cross-type
- Single-point AF, 25-, 72-, or 153-point dynamic-area AF, 3D-tracking, group-area AF, auto-area AF
D750 AF system:
- Multi-CAM 3500 II autofocus sensor module
- 51 AF points including 15 cross-type
- Single-point AF; 9-, 21- or 51-point dynamic-area AF, 3D-tracking, group-area AF, auto-area AF
D500 vs D750: Conclusion
7. Continuous shooting
One of the purposes of this comparison is to show how a DX-format Nikon can give you more for your money than a similarly-priced FX model, and this is most apparent for action photography, where the D500 excels. The smaller mirror and shutter assembly allows high-speed continuous shooting without a massive step up in cost, and the D500 has a powerful Expeed 5 processor and twin cards slots, one of which uses super-fast XQD memory cards. It can shoot continuously at 10 frames per second and capture up to 200 RAW images in a single burst. The D750 cannot come close to this performance.
It’s amazing that you can get a full-frame Nikon DSLR for less than the cost of its flagship DX-format camera, but the D750 is a modest jack of all trades whereas the D500 is a cutting-edge action specialist. The maximum continuous shooting speed of the D750 isn’t bad, at 6.5 frames per second, but this is some way short of the D500’s flat-out performance, and the D750’s buffer can only capture 15 14-bit lossless compressed RAW files in a burst. It can’t match the D500’s speed and endurance, and the only FX camera that can is the Nikon D5, which costs three times more at £5200/$ 6500.
Conclusion: D500 or D750?
The D500 is an out-and-out sports specialist that easily outperforms the D750 for action photography. It might seem expensive for a DX model, but you’re getting (almost) the performance of the Nikon D5. But while it’s perfect for telephoto photography, the relative lack of pro-spec shorter focal length lenses means the DX format has limits for other areas of photography.
FX cameras are expensive, so it’s no surprise that all you can get for D500 money is a relatively modest all-rounder in the D750. But while it can’t keep up with the D500 for action photography, the D750’s larger sensor delivers images with a little more spatial depth and – more importantly – it’s compatible with a much larger selection of pro lenses. Ultimately, it’s the system with most potential.
This feature was originally published in N-Photo Magazine, to subscribe, click here