D3s was ranked 1st in low light performance by DxO. The 2012 sensor tech used in the D4 is cutting edge by means of maximizing sensor's microlens light transmission and microlens shape in order to gather and focus all the available light on the CMOS area which has also been improved over the D3s. Low light performance is not only about ISO, it's about how much DR would be achieved in that settling, how much color sensitive it would be etc. Nikon has it's own standards in determining how high it will rate the normal sensitivity. The photograph taken with ISO 12800 can be printed large and nobody will notice it is taken at that setting, it will look just the same as it would be taken with ISO 100. Nikon gives the indicated quality at 16MP, that's D3s+4MP, usable for unseen until now detail at all normal sensitivities, and fair results at ISO52k and 102k (Hi - modes), which by my opinion give charm or charisma of a photograph (little bit of noise). By comparison one would achieve excellent poster sized detailed results photographing the milky way at ISO8000 f/4 14mm, 30sec. With the D3s we had this ability, but now we have lots of detail too and even more improved high ISO, the D4 is a marvel, the crown of the camera world.

The question is not how high it gets, but how clean from noise it will be.
If , for example, the 6,400 ISO on the D4 will be as clean as 800 ISO on the D3s - would be awesome!

Blessings from Israel
Eitan

Hi4 is 204,800, without the "hi#"s its 12,800

It's my understanding that the new batteries had to conform to the current Japanese regulations for recycling.

Since the introduction of the D3 a lot has happened in the electronics field, especially with processors and memory. Specialist processors have doubled in performance while the size of the die (each transistor) has reduced by half. Smaller transistors lead to higher speed and less power usage.

The magnets and circuits used to create the motors have much more torque and can operate a lower voltages.

Typically Japenses, design a battery that supplies the right amount of power at the right time.

The only way to correctly assess the performance is to use them in side be side under the same conditions.

Try comparing a torch with a tungsten bulb with one with an LED - the powr usage ratios are so very different - I would reckon the same applies between the D3 and D4 - 4 years is a very long time in electronics.

But the voltage and amperage is lower on the new batteries. They should have made them at least as big (power wise) as the old ones.