A common thing I see written about the D800 or even the D7100 for that matter is "what's the point in all those pixels". In truth I very rarely need them myself as I don't print big, however they are very useful to me for the following reasons.
The thing with points 3 and 4 is that an image should be processed based on what distance it will be viewed. If you print very big and stand a long way back a noisy image will look much better. However, if you view a D800 image at 100%, 18 inches from your eyes and it's anything short of perfect in terms of noise and sharpness and it won't look great. Lots of new owners say they are not impressed and this is why.
The other thing I love about this sensor is the dynamic range and the ability to recover blown or underexposed detail; that's just wow.
- If I ever do manage to take a great image and want to print big I've got it available.
- If I need to crop I've got plenty to play with. Sometimes I take things like buildings with plenty of space around so I can straighten them in post. In reality, if I always need to crop because I can't get close enough I would be better with the high resolution per mm of the D7100 and thats what I use for shooting small stuff, but the D800 gives me the option.
- Noise. This is one of my biggest things these days since I realised the impact of sizing. As most of my stuff goes on Facebook, online competitions or Flickr, the biggest dimension is about 1600 pixels. If I go into Photoshop and change the image size down to this it removes lots of noise. My ISO 6400 images are stunning (in my mind) with regards to noise. I've been a little late realising this, but it now allows me to shoot with a very relaxed attitude to ISO.
- Sharpness - Doing the resize described above also makes the world look sharper.
The thing with points 3 and 4 is that an image should be processed based on what distance it will be viewed. If you print very big and stand a long way back a noisy image will look much better. However, if you view a D800 image at 100%, 18 inches from your eyes and it's anything short of perfect in terms of noise and sharpness and it won't look great. Lots of new owners say they are not impressed and this is why.
The other thing I love about this sensor is the dynamic range and the ability to recover blown or underexposed detail; that's just wow.