Nikon experts please?

What does FX mean please?

It means full frame & is the designation used on lenses for full frame cameras. Full frame means that the sensor is the size of a 35mm negative (as opposed to the 'cropped' sensor, or APS-C size of consumer DSLR's which is slightly smaller).

You can use FX and DX (DX lenses are those designed to be used with a crop sensor camera) lenses on a crop sensor camera; you can also use both on a full frame camera, but when you mount the DX lens on an FX camera, it only uses the central portion so you'll get a smaller image size.

Fx = Full Frame sensor - the same size as 35mm film.

Dx = smaller sensor, about 60% the size of a Fx sensor. Also known as a cropped sensor.

Larger sensors are more expensive to make, so much so that in the early days of DSLRs, most all cameras used cropped sensors. But as time went on, the cost of sensor production has dropped, along with the increase in technology, which makes cameras having Fx sensors less expensive (D600 at around $2, 100).

However, there's still a bright future for Dx cameras. One thing that will not be reduced in price anytime soon is the cost of high quality Fx lenses. Since a camera is the combination of a body and lens, Fx lenses still tend to keep Fx cameras fairly expensive, so many still prefer the lower cost Dx cameras.

Which one you pick is largely up to your pocketbook. Either Fx or Dx DSLR is capable of extremely high quality photographs.

FX indicates the camera has a full frame sensor. This means the sensor is the same size as a 35mm frame.

DX indicates a sensor which is 1.5x smaller than full frame.

DX lenses won't give you full coverage on FX sensors, but FX lenses will give you coverage on both FX and DX sensors.