Taking a selfie at night or in a dark room... we have all done it, did you ever wonder why the image is usually very grainy, and lacking detail?
The tiny sensor behind that small lens on your phones camera is smaller than the size drawing pin, this is very small compared to even a point and shoot camera.
Ever wondered why the Flagship DSLRs from both canon and nikon have moderate mp counts?
A "mere" 16mp for the D4s and 18mp for the 1DX may seem few compared to the D810 and 5DIII R having 36mp and 50mp respectively.
Now the primary reason these £6000+ cameras have these mp figures is, the more pixels the sensor provides, the more noise it will inherently produce also, and these two flagship models are designed to be unstoppable when it comes to low light, and high ISO performance.
The Nikon D4s can, in expanded mode, be used at 409,600 ISO, which it performs staggeringly good at!
Now we should already know that the larger the sensor, the more light inevitably falls on the sensor, especially when comparing full frame 35mm sensors, to the smaller APS-C sensors found in 1.5 and 1.6 times crop factor,
So by that account the full frame sensor will produce less what is called signal to noise ratio, than its smaller cousin.
A full frame D700 will produce cleaner images than a D300s, even though they have the same mega pixels, I know the D700 at 10,000 ISO produces similar amounts of grain to a D300s at 2000 ISO.
So if the sensor size is the same between 2 cameras, say the D50, with its 6.1mp aps-c sensor, along side a D300s, with a 12.3mp aps-c sensor, the smaller pixel count of 6.1 on the D50s sensor will at the same ISO, produce less noise and grain than the D300s, as I will show below.
Here are samples I took from the APS-C D50 (6.1mp), D200 (10.2mp), D300s (12.3), and the full frame D700 (12.1mp) for comparison.
Here I will compare the D300s at 2000 ISO, and the D700 at 10,000 ISO to demonstrate how better off a full frame sensor can be at managing noise.
And finally both cameras at the same 6400 ISO
To summise what you see in the photos, when it comes to low light and high iso performance, the 12mp D700 sensor is a absolute gem of a performer, only outshone by its twin the D3, and the D3s/D4/s bigger brothers, where as the smaller APS-C sensors yet with an identical mp count doesnt perform half as well!