What exactly is going on with Nikon's ISO 100?

Question

The new Nikon D3 and D300 do not go down to ISO 100 with a direct setting. You use the "expanded range" to drop ISO 200 in 1/3 EV values down to ISO 100. Are they cutting sensor amplification or what? I'm curious...

Piano Man, I am thinking along the same lines as you. The D200 goes from ISO 100 to 1600 without tricks. That's a 5 stop range. The D300 goes from ISO 200 to 3200 without tricks - also a 5 stop range. The full format D3 goes to a 6 stop range on ISO, but there must be a lot more room between those pixels on the larger sensor since both the D3 and D300 are 12.1 MP cameras.

Answer 1

From what Ken Rockwell says about "expanded range" is that the sensor captures in ISO 200 and then the exposure is halved by software. Just like using 3200 with the D200 - it shoots at 1600 then uses software to increase exposure - bit like increasing a stop in PS's raw conversion. Why it's not a direct sensor action I don't know but I'm assuming with the technology at date they don't get a good enough range of sensitivities via hardware control. The only analogy I can think of to explain this is the greater zoom range a lens has, the less quality image that can be achieved.

Edit: I'm with you on that. I think having 12 million amplifiers gets a little mind numbing for the electrical engineer and having to increase and lower the gain for each photosite by 5 or 6 stops is an incredible feat. Well, the gain control isn't but the fact that it can be done without introducing too much noise into the equation given the 6 stop range is pretty awesome.

Answer 2

Dunno partner, but my $1.59 roll of expired Konica 100 film is bang-on with my $25 light meter...good luck with it ;0)