What is the difference between Nikon Nikkor AF 50mm f/1.4D and AF 50MM F1.8D Lens?

Well besides the price though…

The 1.4 is faster, obviously. What this means is that the aperture on the 1.4 is wider at its max opening than the 1.8. The faster your lens, the less light you need to shoot and the shallower depth of field you can have.

The f-number denotes the maximum aperture of the lens. The lower the number, the wider the maximum aperture and the more light that can be captured. Lenses are known as "faster" lenses the wider their maximum aperture. Thus, you need less light to shoot with f1.4 compared to f1.8. The trade-off is that you will have very limited depth of field (how much of the shot is in focus) with the wider aperture, but the difference between 1.8 and 1.4 is minimal.

Faster lenses are more expensive to manufacture, are typically larger in bulk, and weigh more too. But the results can be astounding, as it is possible to shoot in almost complete darkness.

Of course, the simple answer is, not a lot - assuming these are both Nikkor AF-D lenses, these are very similar lenses indeed

The 1.4 is faster, build much better and upto f4 it's also sharper than the 1.8

Better light usage…

bigger aperture…

bigger price…

but unless you are a professional, you wouldn't notice the difference, except in you pocket…

1) Build Quality -- Which means

a) Feels better in hand
b) works better
c) more 'pro type'…

2) Faster
3) Better Bokeh
4) 'sweeter bokeh'.sweeter means more soothing to the eyes, smooth.
5) better when you'r tryin it in an environment where you wanna single out something more particularly then anything else.say your nose is in focus but the eyes are not…

get the f/1.4D… Personal recommendation… 1.8/d isn't actually tht cool…

The f1.4 has a wider maximum aperture.