Noise, resolution and sensitivity
The Nikon D800’s native sensitivity range of ISO 100-6400 can be extended at either end, to ISO 50 (Lo1) and up to ISO 25,600 (Hi2), giving a total range of 10EV. In comparison, the D4 extends up to ISO 204,800 for a 13EV range, and the Canon EOS 5D Mark III reaches up to ISO 102,400.
Nikon has made a neat refinement to the auto ISO control, as the camera detects the attached lens and focal length, and adjusts its settings to give the minimum possible ISO to achieve the longest shutter speed for blur-free handheld images.
For example, with a 200mm lens attached, auto ISO sets the shutter speed to 1/200sec and selects the appropriate ISO setting for a ‘correct’ exposure. In most situations this is very accurate and eliminates the need to change the ISO manually (if shutter speed isn’t the primary exposure concern), although this can be achieved quickly via the control on the dial on the top left of the camera.
Given the high resolution of the sensor, I had great expectations for the level of resolved detail and I was not disappointed. The D800 resolves the highest level of detail of any full-frame camera, and comes very close to some medium-format models,.
At ISO 100, the D800 comfortably reaches the 38 marker on our resolution chart, with sections of the lines visible all the way to the end of the chart. Also a pleasant surprise, the level of resolved detail is high all the way to the extended ISO 25,600 (Hi2) setting, at the 30 marker.
While resolved detail is impressive at higher ISO settings, images are not free of noise. When viewed at 100%, luminance noise is evident at ISO 800 in shadows, but it is adequately controlled all the way to ISO 3200 in highlight areas. Beyond these ISO settings, luminance noise steadily increases in shadow and highlight areas.
In the extended ISO settings of 12,800 and 25,600, chroma noise is also obvious, with an array of yellow, red and blue blotches. It is in noise control that the D800 cannot quite match the competition, but this is to be expected to a degree, due to the camera’s high resolution. Images all the way up to ISO 3200 look clean and are perfectly acceptable.
It is possible to use the high resolution to control noise. By exporting raw files in a smaller format (with fewer pixels), the level of noise is also reduced. I shot the same scene at ISO 6400 with the D800 and the Canon EOS 5D Mark III. In full-resolution files, the 5D Mark III controls noise more effectively.
By reducing the output of the D800 file to a similar number of pixels as the EOS 5D Mark III, the difference in noise levels is less noticeable, although the Canon model still has the edge.
These images show 72ppi (100% on a computer screen)
sections of images of a resolution chart, captured using the Sigma 105mm f/2.8 macro set to f/8. We show the section of the resolution chart where the camera starts to fail to reproduce the lines separately. The higher the number visible in these images, the better the camera’s detail resolution is at the specified sensitivity setting.
