There are currently 3 different versions of Nikon 50mm lenses that you can buy new: The 50mm f/1.8D, 50mm f/1.4D and 50mm f/1.4G. In addition to these lenses, there are third party lenses, like Sigma’s very capable 50mm 1.4 HSM, and some older Nikon lenses still in circulation.
Shallow depth of field. Nikon D300, 50mm f/1.4D at f/1.4, 1/160, ISO 200.
If you are using a Nikon DX or 1.5 crop body, like my Nikon D300, the 50mm lens acts like a 75mm: in other words, a short telephoto. I bought mine specifically for shots where I need extremely shallow depth of field, and so I intend to use it wide-open or close to it. I can also use it for low light shots, although the short telephoto focal length will make it a bit cumbersome to work with for general low-light shooting.
A low light example: Releasing a lantern during Loy Krathong at Krabi, Thailand. Nikon D300, 50mm f/1.4G at f/1.4, 1/200, ISO3200.
Which one did I get? I bought all three, tested them, and ended up keeping the new 50mm f/1.4G.
My main problems with the older ‘screw-drive’ versions, the 50 f/1.8D and 50 f/1.4D, was that they had a higher tendency to misfocus on my D300, and focusing accuracy is critical when shooting with shallow depth of field. The new 50 f/1.4G, despite being equipped with a supposedly faster AF-S focusing system, actually focuses slower on my D300, but is much more accurate.
Who likes a big wet kiss on the face? Nikon D300, 50mm f/1.8D at f/1.8, 1/2000, ISO 200.
I really wanted to like the cheap and light 50 f/1.8D, but I had some bad front focusing issues with it, and the lens tended to be quite soft wide open closer to the edges.
I’m hesitant to recommend the 50mm f/1.4G outright. Not only is it the heaviest, it is also the most expensive. In fact, for a 50mm prime lens, it is absurdly expensive. Quality control also isn’t that great. All three ‘Made In China’ samples I looked at had dust inside the lens, which means it happened during manufacturing in the factory.
If you can afford to stop the lens down a little, say to f/2 or smaller aperture, and you’re happy with the focusing accuracy, I’d say take a closer look at the older 50’s. If you must have the best, the new Nikon 50mm f/1.4G is the best in terms of overall performance, but you’ll pay through the nose for that performance ;o)