Editors' note: This story was originally published in a different form on March 20, 2014. The most recent update includes review-based recommendations for the D3400.
Not everyone approaches the dSLR buying decision as a tabula rasa choice. If you've already chosen Nikon -- whether it's because you already have some lenses, your friends are enamored of the brand, or you simply have had good experiences with the company's point-and-shoots -- here's some help selecting the right dSLR model.
On a general note: if your budget is tight, and unless there's a specific feature or performance level you need from a particular model, it's usually a good idea to save money on the body and spend it on a better lens.
Still to come: the D5 and D810.
The last-generation entry-level dSLR in Nikon's lineup, the D3300's price has finally dropped below (or gotten very close to) that of the D3200, rendering the much older D3200 a forgettable option; with the older 18-55mm II kit lens the D3300 costs about $500 (£400, AU$500) or £370/AU$550 with the AF-P VR kit lens (I can't find the same kit in the US). Because old D5200's price has started the upward trend that indicates it's disappearing from the market, it's about $200 (£50, AU$150) to step up to a significantly better autofocus system in the D5300.
A much better value than it used to be, the Nikon D5300 kit with the 18-140mm f3.5-5.6 lens is the best overall choice under $1,000 (£815, AU$1,300) with a more affordable $700 (£630, AU$850) price, at least in the US and Australia. The body delivers better photo quality than all the cheaper cameras (and similar quality to the D7100/D7200), as well as a much broader feature set that includes GPS plus slightly better performance. While the lens is technically still pretty slow, it covers a much broader range and is a lot more flexible -- especially if you only plan to use one lens. The D5300 with the 18-55mm VR II lens ($700, £450, AU$650) is also a better buy than the D5500 ($750, £540, AU$1,000) for the kit with the same lens if you have big hands or don't miss the touchscreen and Wi-Fi.
The D5500 $750 (£540, AU$1,000) for the kit with the 18-55mm VR II lens is very similar to its predecessor -- same video and photo quality and I suspect the same performance (I didn't have a D5300 in-house to retest with our new methodology). It's slightly smaller, and the redesigned grip may not be comfortable if you've got large hands.
I qualify this with "modern" because the old D5300 kit with the 18-140mm lens $700 (£630, AU$850) is an overall better choice. Plus, I don't like the 18-55mm VR II collapsible lens very much. However, if you feel the need to only buy current-generation products, the D5500 is a good choice.
The least expensive choice for action photography, the D7100 is a great camera, delivering better photo quality, performance, and improved weather sealing than its predecessor. That said,folks who don't need the build quality or the extra continuous-shooting speed might be better saving some money over the D7100's $700 (£560, AU$900) body-only price tag and opting for the D5300 18-140mm kit $700 (£630, AU$850. The newer D7200 (body $870, £700, AU$1,100) is almost the same camera with only minor updates -- the only important one is a better continuous-shooting buffer -- but a higher price.
It's hard to really differentiate the D7100 from the D7200: the D7200 has slightly improved photo quality and a deeper continuous-shooting buffer, which makes it a marginally better choice for dim light and long-burst photography. And it has a few updated features, including time-lapse movies. It's a good camera, and the price has finally dropped into great-buy territory at $870 for the body, at least in the US. It's still significantly more expensive than the D7100 in the UK and Australia, though (£700, AU$1,100).
The full-frame D610 competes with the more expensive D750 ($1,900, £1,700, AU$2,500), and the latter is a better camera in many ways. But if your budget's tight, this approximately $1,500 (£1,150, AU$1,800) body is worth the step up to full-frame from APS-C; it gives you access to a larger selection of wide-angle focal lengths (no crop factor) and extremely shallow depth of field in situations where it might not be attainable with an APS-C camera.
The trade-off is that decent lenses are more expensive for this model than for the D7200. While the D610 supports both DX (APS-C) and FX (full-frame) lenses, to get the most out of this camera you need to use more upscale glass.
With a great feature set, excellent performance, photo and video quality, plus a solid design, the D750 ($1,900, £1,700, AU$2,500) earned an Editors' Choice Award for general-purpose prosumer cameras under $2,000 (£1,635, AU$2,625). It has a lot of advantages compared to the more-expensive D810 ($2,800, £2,000, AU$3,200) and better photo quality than the D500 ($2,000, £1,650, AU$3000), but only a few drawbacks. If you have room in your budget, it's worth it over the D610 ($1,500, £1,150, AU$1,800), but you might also find it worth it to spend the difference on a better lens.
Though it costs more than the full-frame D750 ($1,900, £1,700, AU$2,500) the APS-C-based D500 ($2,000, £1,650, AU$3000) is a different beast. The D750 is really a general-purpose prosumer camera, while the D500 is best suited as a camera for shooting action and manually focused 4K video, making it the best choice for big-budgeted bird and sports prosumer photographers and action-shooting pros on a really tight budget. It's fast, with excellent autofocus and great photo quality (for APS-C). The 4K video quality is excellent, but the autofocus in video isn't great.
Although I haven't reviewed the D810, I have tested it. While its filter-free sensor delivers sharper photos with better dynamic range, compared to the cheaper D750 the $2,800 camera (£2,000, AU$3,200) has only a few other advantages. It maxes out at one stop faster shutter speed (1/4,000 sec. vs. 1/8,000 sec.), and it has a higher flash sync of 1/200 vs. 1/250 sec.
It's a bit of a niche, but the D810A ($3,800, £2,900, AU$4,500) is a version of the top-of-the-line D810 optimized for astrophotography with an IR cut filter and some expanded features.
This now last-generation double-grip full-frame model is still great for sports shooting, but the D5 which replaces it has a lot of important enhancements: better continuous shooting, much updated autofocus system, two extra stops of ISO sensitivity in the native range and two in the expanded range and 4K video, to name a few. The price isn't as low as it had been earlier this year, but at $5,000 (£4,200, AU$7,000), it's still a good buy if you can't afford the D5 ($6,500, £5,400, AU$7,000 for the CompactFlash version) -- at least in the US and UK.
If you're really cash strapped, I suggest that you look for a used model since a lot of people will likely be selling them to buy a D5, and used pro cameras retain their value pretty well.
While I haven't finished testing it yet, I the D5 has the best Nikon autofocus and metering system specs to date, at 12fps it's the fastest Nikon as well (though the typical continuous-shooting speed is 10fps and it only hits 12fps under specific circumstances), and it's the first Nikon to offer 4K video. You'll pay for the privilege, though at $6,500, £5,400, AU$7,000 for the CompactFlash version. It comes in two models which differ by storage media: one with two CompactFlash slots and one with dual XQD slots, the fast but not widely supported media format introduced in 2010.