So, some time later, Nikon launch the D7200 offering a 24mp sensor and 6fps - so what is the difference and is it worth the upgrade?
D7200 offers a new 51-point AF system which is far more sensitive that the D7100 which promises faster and more accurate AF especially with slower lenses or in poor light- the D7200 will now operate down to -3EV.
The buffer size has also been substantially increased - by a factor of between 3-5x depending on settings-so you can take far more shots in continuous mode than with the D7100 before the camera pauses to write to the card. 100 Jpeg fine images at 6fps is now possible.
The sensor too is a new sensor unit which again promises improvements in low light performance and noise control and the full ISO range is now native at ISO 100-25,600 whereas with the D7100 above ISO 6400 was only available via expansion settings.
The imaging processor has moved from EXPEED3 to EXPEED4 which enables all these improvements.
There are a few other refinements - with a clarity setting added to the picture control customisation menus - which adds local congrats to fine detail in your subjects and built in WIFI and NFC.
My standard airshow lens is the superb Tamron 150-600mm f/4.5-6.3 Di VC USD. With the D7200/D7100 in DX mode this gives a full frame equivalent of 225-900mm or in 2x crop mode up to 1200mm. The VC system is highly effective and the USD focus motor does a good job keeping up with fast moving subjects.
For airshows I tend to shoot in Manual mode fixing my shutter speed at around 1/320-1/400 for propeller aircraft (to get propeller blur) and 1/1000-1/200 for fast jets. I set the lens aperture around F10 to get a fraction more depth of field and to maximise lens performance at 600mm, I then set Auto ISO on the camera so the exposure is controlled by raising or lowering the ISO. For this test I also set the clarity setting to +1 in the picture control and had D-Lighting switched on (auto setting).
Taking shots of aircraft on the ground I could immediately see that the focussing was snappier with the D7200 and there certainly was an increase in fine detail with the clarity setting increased in the picture control.
Moving to aircraft in the air, the D7200 provided me with the highest hit-rate of images in focus I have ever achieved at an airshow - testament to the improved AF system.
With the D7100 I often find that I run out of buffer when shooting aircraft - especially if I shoot in Raw - with the D7200 no such problems. Throughout the day I was able to shoot freely without worrying about the camera suddenly stopping as the buffer was full thus preventing me from getting shots.
So, if you are a D7100 owner should you upgrade? If the higher buffer size, better high ISO performance and WiFi are important to you then yes. If not, then the D7100 remains a great camera and you can mitigate the buffer issues by shooting fine Jpegs rather than raw files and turning off features like distortion control, D-Lighting and shade compensation which all use up processing power. Both cameras benefit from using the fastest possible SD cards - UHS-1 or UHS-3 with 95mb or faster write speed are the ones to go for.