Nikon 50mm f/1.8G looks different from f/1.2 or f/1.4G. What is that extra labeled scale that makes it look different?

Nikon 50mm f/1.2

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Nikon 50mm f/1.4G

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Nikon 50mm f/1.8G

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These are completely different designs from decades apart. The F/1.8G and F/1.4G have a window to show the focus distance because the camera can control it via autofocus. When the camera drives a lens like that, the focus scale rotates within the window. The user can also turn the focus ring itself to change the focus distance.

The F/1.2 has a direct focus ring which is labelled in both meters and feet. The user turns it until its set to the desired focus distance. The camera cannot change it. There is also a second ring to control the aperture, closer to the mount. While you control the aperture directly, Nikon DSLRs can still meter with it properly. Since aperture control is manual, you can only use it in Aperture Priority or Manual mode, but that depends on the particular camera. From the comments:

For Nikon lenses with the aperture ring on the lens, they can still be used in P and S modes on the pro / prosumer line cameras (like D800). Just set the aperture on the lens to the max (f/16 in this case). Some lenses have a lock you can engage to keep it fixed there. On the lower end consumer cameras (like D5100), you can only use those lenses in M mode. (Not even Aperture Priority)

  • F/1.8G or F/1.4G has a similar focusing mechanism as my 18-55 kit lens. Right? I can't get what you mean by "window". Is there a similar "window" on my kit lens, too? Jun 17 '16 at 3:00
  • You see in your photos where the infinity symbol is? That is behind what I call a window. When the camera changes the focus distance, the focus ring does rotate but the label shown behind the window will. No, the kit lens probably does not have a window, although there are a number of variations, so I don't remember if none of them have it.
    – Itai
    Jun 17 '16 at 3:12
  • Now I understand. Yes, my kit lens doesn't have such a window. A quick question. For lenses (e.g. f/1.2) which does not have an in-lens motor (e.g. SWM), do they always have such an aperture ring to control the aperture manually? In other words, if the lens can't be auto-focused, it's aperture, too, can't be set by the camera, right? Jun 17 '16 at 4:49
  • No. The AF has nothing to do with whether there's an aperture control ring. The "G" in the 1.4G and 1.8G lenses names means "Gelded", having no aperture ring.
    – scottbb
    Jun 17 '16 at 11:53
  • 1
    As @scottbb said, no. Those are two separate things. There are manual focus lenses without aperture rings and there are autofocus lenses with an aperture ring too (sometimes those have an A position to auto aperture as well, I don't recall if there is a Nikon lens like that but it exists).
    – Itai
    Jun 17 '16 at 12:17

The extra scale is a depth of field scale. It's basically using slide ruler technology against the distance scale to let you set your DoF the way you want. The symmetrical numbers are for a given aperture setting. If you set the one number against one distance, them matching opposite number tells you the other end of the DoF, in distance. To set hyperfocal, you would put the infinity sign (∞) opposite the f-number you're using. Using this scale is known as zone focusing (see also: Is it possible to Zone Focus with a DSLR?).

Also see:

  • All the lenses shown have a depth of field scale under the focal distance. It's just not as clear with the newer ones
    – tschundler
    Jun 18 '16 at 3:44

The twin row of numbers is the Distance Scale. The Depth of Field scale is the unlabeled set of inscribed lines in the silver ring behind the distance scale to right & left of the black focus point indicator dot. These lines show the depth of field when the aperture is set at f/5.6, f/11 & f/16. In this image the lens is focused at just under 1.2m, the aperture is set at f/5.6 and the depth of field range is shown by the two lines closest to the black dot which point at the near (right line) and far (left line) ends of the range as shown on the distance scale. If you look at a color picture of this lens the pairs of DoF lines are color coded to correspond to with their f/stops.

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