There is not enough difference between a D90 and a D300 to get excited about. That's the word I got back from Thom Hogan tonight when I asked him directly about this
I would be very
excited about half stop difference.
anyone who thinks they will get noticeably better performance from a D90 than a D300 is misinformedBased on the raw image I have
it is you, who is misinformed or uninformed.
Arguing that someone who is not getting results they are satisfied with at ISO 1600 with a D300 would be satisfied with a D90 instead is setting them up for disappointment; the same is true at base ISO as it pertains to DR
On what do you base your assessment? On how two anyway not noisy images compare as "whole"?
Regarding the issues of not using the same lens, the same focal length, or the same EV; that highlights the lack of rigorous control at Imaging Resource and which is manifested by the 1/3 of a stop discrepancy in their comparative files
You don't understand the very basics of measuring
the noise. If you give me two shots with the same ISO, containing smooth, unicolored, evenly lit areas in the very shadows, the best if several such spots in different darkness, I can measure and compare the noise, no matter which camera, which lens, which scenery, which illumination.
The layers of the TIFF I linked above show the principle of measurement: the noise is measured relatively to the actual pixel level in an area, on the raw channel. It does not matter which color, which lens, whatever. What matters is how high the pixel level and how high the noise is. If I find such areas with closely matching pixel levels, then the noise level shows which sensor is better. If I find areas with the same noise level, then the difference between the relative pixel levels shows how "much" one sensor is better than the other. (One needs to take several samples for a reliable result.)
I uploaded a compilation of such measurements as an Excel chart
(the 5D2 data is not reliable); this is only as demo, it does not include the D300 nor the D90.
Can you see a difference in the lighting between these two?
This is irrelevant. For example at ISO 200 neither the D300 nor the D90 images from IR can be characterized as noisy at all. However, those images are suitable to measure the noise level and predict, how the sensors compare at ISO 200 if the shot contained severally underexposed areas. That is, what dynamic range is about.
Pick very dark areas (smooth, etc. as described above) from any ISO 1600 image and measure the noise; the consolidated result shows, what you can expect in a really low light situation. If the noise in one sensor is the same as in the other but on a half stop darker area, then the first one can create an equal image in lower light, or a less noisy image in the same light (assumed, that the ISO calibrations are equal).