« on: August 21, 2014, 02:43:46 PM »
So let's use a hypothetical example... and both cameras use the exact same lens...It's not really the size of the sensor that counts, it's the size of the pixel.
That's precisely back to front, Don - pixel size doesn't matter one little bit in terms of a sensor's light-gathering abilities, in any practical sense. Sensor size is the whole story, at any given "state of the art".
Jon Rista must've explained this about a million times on here - and he's completely, demonstrably right. Simply put, a big window lets in more light than a small one, whether it's made up of one pane of glass, or many - a perfect sensor analogy in this context.
You use the exact same technology to manufacture a pair of sensors. One is a 10Mpixel APS-C sensor, and the other is a 25.6Mpixel FF sensor. The pixels on the two sensors are exactly alike. Both will have the same electrical characteristics and both will have the same optical characteristics. They will have the exact same noise, the exact same ISO performance, the exact same DR..... because they are exactly the same.
Obviously, the FF sensor takes in more light, but it is spread over a wider field of view and the light per pixel is the same.
You use the exact same technology to manufacture a pair of sensors. One is a 20Mpixel APS-C sensor, and the other is a 20Mpixel FF sensor. The pixels on the FF sensors are 2.56 times larger than the pixels on the APS-C sensor. In this case, the FF sensor receives 2.56 times the amount of light. It's performance will be about 1 1/3 stops better than the APS-C sensor. This is your typical scenario when comparing sensor sizes.... both are near the same pixel count and the added real estate lets you make the pixels larger on FF....
The Sony A7S. Larger pixels. ISO409,600. nuff said...
Either way, it is the pixel size that matters....
FF does not perform better because it is larger, it performs better because the pixels are larger. The larger sensor size allows you place a similar number of pixels of greater size. It is a subtle difference.