Anyone who has a digital single lens reflex camera, dslr will have either a dx or fx sensor. The dx (Nikon) sensor is smaller than fx (Nikon) which relates to the 35mm film format 36x24mm. Nikon introduced their first digital dslr in 1999 which shot 16 x 24mm frame. When sensors started to have 10 megapixels, there were too many pixels for the size of the sensor. Because the pixel’s were so squashed together, they collected less light and produced more noise or grain.
DX sensors are roughly 1.5x smaller than 35mm film, although some are 1.3x. They will show an area equivalent to the area shown by a lens 1.5x as long on 35mm film, this is called the 1.5x crop factor. A 100mm lens on a dx camera shows the same area of view that a 150mm film or full frame, fx, camera. If you tried to use a dx lenses on a full frame of film camera you would get black out corners.
In 2007 Nikon introduced their first fx full frame camera, Nikon D3, the following year the D700 was launched. All Nikon’s will work fine with all their lenses, even their manual one.
The D3 and it’s later version the D3s, launched in Oct 2009, still use 12.1 megapixels. There are other fx cameras which boast more megapixels. Indeed Nikon D3x has a whopping 24.5 megapixels. So if you have a dx camera with 16.7 megapixels you would think that the images would be sharper. Well, there more to size than meets the eye. Bigger pixels collect more light and more light means a cleaner image. This means that they can collect more light in a given period of time. If you have a large sensor with fewer pixel then they can spread out and catch more light. So the larger camera doesn’t have to amplify them so much for the same ISO sensitivity.
Before digital entered our lives, professional photographers either used medium or large format. A 6x6cm ,5″x4″ or 10″x8″ negative or transparency would provide a more superior result than a 35mm. Nothing has changed since.