Jan Anne: Thank you. I thought that some info about the D5 might be of interest to the community (being curious by myself
)
Frank:
Better AF with slow lenses?
Why not.
It is not always speed what counts. Finding a contrast pattern in low light is more dependent on the AF system than the speed of the slow lens. What is more important is
a) that the lens is not decentralized, especially if it is a fast lens - this introduces a long list of issues on AF accuracy with cross-type AF sensor fields
b) the AF system is not spectral sensitive (i.e. the AF of the D3 and others from this period is impacted by different spectral distributions). The D5 seems to be fine in this sense what I've seen initially.
wrt to larger pixel and better DR:
I am sorry to say, that this saying (coming from the CCD days) was carried over to the CMOS world and seems to never die. Good DR is dependent on 2 major things: High Full well capacity and low read-out noise. The reason the D800 became such a success, because it excelled in both vs. the D3 and D4 (not surpassing everywhere, but getting very close). Both, D3 and D4 had a sensor design with an external (fast) A/D converter. This converter has to transform the analog values for all pixels serially. Given the high speed, high precision is very hard to achieve in an economical way. The Sony sensor Nikon used for the D7000 and the D800, has a lot of parallel A/D converters on chip. 2 benefits: 1) each one has a lot of time for the conversion (relatively speaking) and 2) what is integrated on a chip is easier to be calibrated. If interested, look up Sony's whitepapers about ramp wave conversion for more info. This provides excellent (=low) read noise levels for these type of sensors.
On the full well capacity, it is true that larger pixel can register more photons/electrons in the larger pixels. But there are fewer of them on a given sensor size. Let me suggest a different and simple metric, which served me well in the past to understand sensor performance. Full well capacity per full sensor area. According to
sensorgen.info, the D4 has a full well capacity per pixel of 118.339, the D800 of 48818 and the D810 of 78803. Multiplied by the number of pixel on the FX chip gives you the following "light budget":
D4 = 1.912.812.661.760 registered photons FWC for the whole FX sensor
D800 = 1.764.883.957.760
D4s = 2.076.875.637.760
D810 = 2.848.911.272.960
D750 = 1.971.670.171.648
Given that equal output size should be considered in such comparison, this simple number helped me in the past to get a rough estimate how a sensor will perform relatively to others. Just an initial estimate.
For historic comparison:
D2H = 84.277.315.584
D3 = 610.194.772.992
(This is one contributing factor why you can pull so much out of the shadows of an D800/D810/D750/D600 image vs. their ancestors)
Don't know if the real ISO base went up for the D5 (vs. indicated ISO Setting). Bill Claff uses set ISO levels, DXOmark uses measured ISO levels and DXOmark numbers aren't out yet.
rgds, Andy