Also, I assume that D800 and D600 do not allow as high ISO as the 5DIII because noise at those ISO value would be unacceptable. Is this a wrong assumption?
While all these cameras hypothetically support shooting at these immensely high ISO values, in practice, you'd never want to go so high unless you were only trying to get something barely usable when you shrink the picture down mercilessly.
Also, here's a trick to keep in mind. When you shoot raw, there's no such thing as the camera restricting the ISO. Instead, the sensor gets what it gets. If you shoot at the base ISO, then the high bit may well be one or zero. If you shoot one stop faster, then (assuming you're not blowing highlights) the high bit will always be zero. Basically, you're left-shifting the results by one bit. You want to shoot four stops faster? Left shift by four. The more you shift, the more you're digging into the low-order bits, which give you progressively less useful information.
Can you elaborate a bit more on this? This is very interesting.
I understand what you're saying, but isn't that true only limited to one specific sensor? In other words, if you take SensorA and shoot at ISO 800 instead of ISO 100 specifically to reduce the time the shutter stays open, then you are obviously exposing SensorA to less photons, therefore losing information (high bit will be zero) compared to a longer exposure at ISO100.
But, aren't different sensors responding differently? Isn't the point of sensors/cameras reaching ISO 25.000, for example, precisely the ability of those sensors of retaining more information out of that shorter exposure to photons?
In other words, would I be wrong in assuming that a Canon 5DIII "SensorB" will have LESS zeros at high bit at ISO 25.000 at 1/320 shutter speed, for example, than the Nikon D800 "SensorA" at those same settings (if it could reach that high ISO)? If so, then I'd rather have that possibility, which I assumed was the whole point of such sensors compared to competition. And I *think* I saw some nice pictures at high ISO from the 5DIII, but may be wrong there.
What am I missing?
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