fly1 wrote:
> Hi Guys,
>
> It has been mentioned on many threads that the D300 has better pixel
> density than the D700 and this is better for shooting birds and
> wildlife,
>
> Why is this so? one would think a camera at the "high end" would be
> able to produce better image quality?
>

First, apologies for clogging your thread with a discussion not directly related to your OP; I tried to set the record straight on Steve Denton's initial reply, which didn't answer your question correctly IMO by bringing pixel density into the picture. This has set off a colloquy on the relevance of pixel density, which is not so relevant to your original question.

And, I didn't answer your initial question, so let me remedy that now.

Two of the aspects of image quality are resolution and signal/noise ratio. Larger sensors capture more photons, which leads to higher S/N ratio in the image. This assumes that the comparison of a larger sensor camera and a smaller sensor camera is made with focal lengths that lead to the same framing of the image -- then the subject occupies the same proportion of the frame for both, but the actual area the subject occupies on the sensor will be larger on the larger sensor camera; for the same shutter speed and aperture, the larger area collects more light (more signal), noise is thus less apparent, leading to higher image quality to the extent that lower noise is an important criterion. Notice that pixel size by and large doesn't enter into this particular metric of image quality -- for instance the D3/D700 and the D300 collect about the same amount of light per unit area (ie the sensor efficiencies are fairly close; the D3/D700 do have about a 1/3 stop advantage in per area photon collecting efficiency, but that's not a huge difference, certainly not as big a difference as that conferred by having over twice the sensor area, an over one stop advantage).

However, in the context of birds and wildlife, one is often focal length limited -- using one's longest lens, perhaps also with teleconverters. Then one doesn't have the option of having the same framing for large or small sensors. At fixed focal length, as long as the subject fits inside the frame, the subject occupies the same area on the large sensor and the small sensor, and so S/N will be about the same (and in particular *independent* of pixel size as I have explained elsewhere in this thread). Then the major discriminant of image quality is resolution, which is governed by the pixel pitch -- the more pixels on the subject, the better resolved details of feathers etc will be. In this situation, the D300 has an advantage over the D3/D700 due to its smaller pixels. A hypothetical high MP count, FF D3x would provide the best of both worlds -- allowing high resolution in focal length limited situations, and high S/N when one can fill the frame with the subject.

Finally, I would like to emphasize that sensor size and pixel size are relevant, but to these two different aspects of image quality --

1. Sensor size controls S/N in the image and has no bearing on resolution;
2. Pixel size controls resolution in the image and has little or no bearing on S/N at a given scale in the image, assuming comparable levels of sensor technology.

--
emil
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