Bottom Lines Up Front:
1. Sensor subsystem performance (Senor Rating) matters...A LOT.
2. High performance sensors can alter what and how you shoot.
My Basis of comparison
Nikon D300 (DxOMark 67 overall)
Nikon D7100 (DxOMark 83 overall)
Nikon D810 (DxOMark 97 overall)
Last night, I took the new D810 out to exercise it in a non critical situation shooting high school basketball. I very rarely shoot indoor sports. Mostly I'm a baseball, softball, soccer shooter as far as sports go. I popped the 24-70mm f/2.8 as I was just playing. Normally, shooting indoors, I would opt for fast f/1.4 - f/1.8 primes.
I was shooting in Manual mode, RAW, but mostly JPG (Large, Fine, Neutral) with Auto WB and Auto ISO. Image ISO ranged from 400 to 6400. With the D300 I hated shooting over ISO 800 and with the D7100 I always tried to stay under ISO 1600. While I wish I had taken a couple images at base ISO 64 as a control, all I can say is that the image quality blew me away. The D7100 has one of the best APS-C sensor subsystems and the D810 quality just blows it out of the water!!
Normally, shooting sports, I would opt for the APS-C for getting more pixels on target and sacrifice some image quality. Now seeing how much better the D810 is than the D7100 (and that much better than say the Canon 7DmkII) that decision isn't automatic at all. In fact, the D810 with 36MP still provides a 15.6MP DX 1.5 image crop mode and a 25MP 1.2X crop mode. In addition, it obviates the need for a different set of lenses. I am willing to shoot with smaller apertures at higher ISO too. The speed of the D810 was also fast enough for how I shoot sports even though it only shoots 5 fps in FF and up to 7fps in DX crop mode.
I've already been in discussion to sell the D7100 and while I will evaluate the D9300 if it ever appears, it would have to provide a 24MP sensor of similar quality of the D810 to tempt me to buy. The D810 is a game changer for me. I love this thing.
BTW, I did not find dealing with the 36MP images a big deal. I usually convert using ACR and edit in Photoshop CS6. I have a Trancend USB 3.0 card reader and Lexar 1066x 32GB CF and Lexar 600X 32GB SD cards in the D810.
