Can I use Nikkor AI and AI-S manual focus lenses on my Nikon DSLR? Yes, you can!

Virtually all Nikkor lenses produced since the introduction of AI in 1977 can be mounted and used on virtually all Nikon cameras produced since 1977, because the Nikon F-Mount has remained fundamentally unchanged since 1959.
In other words: Nikon DSLRs are almost 100% backwards compatible with Nikkor lenses back to 1977...
That this is no small feat, is particularly well demonstrated by the fact that Canon have had to change their mount 5 times in the same period (R, FL, FD, new FD and EOS), while these mounts are not always backwards compatible.

Mounting a lens on a camera is one thing, however, can you actually shoot with it? Yes you can!
The following manual focus (non-CPU) lenses and accessories are compatible with the D40, and if they are compatible with an entry-level camera, they ought to be compatible with most everything else.
• AI, AI-S, E-series
• AI-P (post-chipped AI)
• Medical 120 mm. f/4
• Reflex Nikkor
• Nikkor PC (perspective control)
• AI tele-converters
• PB-6 bellows
• PK-11A, 12, 13 and PN-11 extension rings.

Note 1: If you are any good at DIY, you might want to try to “chip” your lenses with a so-called “dandelion”. For more information about the chip, click here, for detailed installation guidelines click here.
Note 2: on Nikon cameras without a built-in focusing motor – D40(X), D60, D3000 series and D5000 series – Nikkor AF-D (motor-less, non-AF-S) lenses work only in MF mode, with two exceptions: the 17-35mm f/2.8D and the 300mm f/4D.
However, because these are cpu lenses, they will meter-couple and can be operated from the control dial(s). Remember to block D-type lenses (with aperture ring) at their smallest aperture – typically f/22 – to avoid getting a fEE error.

To find out exactly what usability a particular lens has on your camera, I'd strongly suggest you consult your camera manual, because more than a few lenses and accessories have their specific limitations.
Still, as a rule of thumb, the following:
To function properly on a DSLR, AI, AI-S, AI-P & E-series manual focus lenses ought to have an f/max. of f/5.6 or less (f/4, f/2.8, f1.8, etc.), with the exception of some of the recent models, like the D7100, D4S and D810, which achieve AF on one or more of their focus points with lenses or lens-combos with a minimum aperture of f/8 (see this article for more info)
When a lens is used in combination with an accessory (bellows, extension rings, tele converter, etc.) the combined f/max. should not exceed f/5.6 (f/8), either.

Compatibility and functionality.
• Nikon D1, D1H, D1X:
AI, AI-S, AI-P & E-series MF Nikkors can be mounted and used with either aperture priority or manual, center weighted, auto exposure metering.
Aperture is not indicated in the viewfinder and/or control panels (F- -), lens data (lens description, max. aperture, selected f-stop, focal length) is not included in Exif.

• Nikon D2-, D3- and D4 series, D200, D300(S), D700, D600-, D7000- and D800 series:
AI, AI-S, AI-P & E-series MF Nikkors can be mounted and used in either aperture priority or manual mode, with center weighted, auto exposure metering.
Once the user includes lens data (max. aperture, [min.] focal length) in the camera’s lens database, the selected f-stop will be indicated in the viewfinder, control panel(s) and aperture priority auto exposure with color matrix metering becomes available.
Aperture cannot not be controlled from the camera body with the control dials and must be set manually.
Lens data (lens description, max. aperture, selected f-stop, focal length, etc.) is included in Exif.
The camera's lens database can be accessed through the Shooting Menu > Non-CPU lens data, or – alternatively – assigning the FN button to this function (D200, CSM f4; D7100, CSM f2: assign func. button > lens data), in which case the focal length and f/number are set with the main and secondary control dials.
All mentioned cameras automatically select A-mode when a non-CPU lens is attached, with exception of the D600 and D7000 series, where A- or M-mode must be set manually. Else the camera will refuse to fire.

• Nikon D40(X), D50, D60, D70, D80, D90, D100, D3K- and D5K series:
AI, AI-S, AI-P & E-series MF Nikkors can be mounted and used in Manual mode only (you must set the Mode Dial to M), the exposure meter does not work.
If the camera is not set to M-mode, it will not fire and show a blinking F-- symbol in the viewfinder and/or control panel(s)
Aperture is not indicated in the viewfinder and/or control panel(s) and lens data is not included in Exif.

However, it is quite easy to shoot without metering on a DSLR.
In normal daylight, start out with ISO 100, f/8 @ 1/125 s., review your histogram and/or blown highlights overlay in image review and adjust your shutter speed and/or aperture until achieving correct exposure. Remember that manual lenses may be set in between full stops (clicks).
After some practice you will get better at “guessing” quickly.
In all cases the electronic range finder DOES work, just make sure the green dot (4) at the extreme left hand bottom side of the viewfinder goes steady to assure proper focusing.

How to identify a manual focus Nikkor lens?
By focal length, f/ number (maximum aperture: f/1.8, f/2.8, etc.) and serial number, here.

Visually:

- AI:
Screwed-on, semi-circular, pre-AI aperture coupling prong with cutouts.
Aperture ring with Aperture Direct Readout (ADR) scale (an additional series of small f-numbers engraved on the aperture ring). This is by far the easiest way to identify (in)compatible lenses, because pre-AI lenses lack the ADR scale.

Thus, if you have a MF lens without an ADR scale, and with thick, and/or triangular, and/or uncut coupling prongs, either fixed or screwed-on, it is pre-AI or NAI and should NOT be mounted, or it will most likely damage your camera!
Although they can destroy the mirror in exceptional cases, with most cameras the damage may not be noticeable at first sight, because pre-AI lenses typically tend to deform or break the exposure meter coupling lever or the minimum aperture confirmation notch (or lever) on cameras that do not meter-couple with non-cpu lenses (D40, D60, D90, etc.).
Even if on some cameras like the Nikomat FT3, Nikon EL2, FM, FE, F3, F4 and now the Nikon Df, the meter coupling lever can be released and moved out of harm's way, on the large majority it cannot.

- AI-S. Identical to AI, plus:
Lens type identification gouge - a small semicircular indentation on the F-Mount (fig. 4, right).
Smallest aperture number marked in orange on the ADR and aperture scales. Note that some pre-AI lenses may have this number marked in light blue or sometimes green, which is another way to identify them as not compatible.
All modern Nikkor lenses are AI-S compatible, while AF-D and AF-S D-type lenses (with aperture ring) include a smallest aperture lock (L) button (fig. 5).
On cameras with control dial(s), these lenses must be set to their smallest aperture and locked.
If the lens is not locked at its f/min. (typically f/16 or f/22), the camera shows a blinking fEE symbol on its control panel(s) and will not fire.
AF-S G-type lenses (without aperture ring) are fully compatible with electronic camera control, and no user intervention is required.

- Series E:
A series of more economical lenses, marked “Nikon Lens Series E” not “Nikkor”. The very first AI-S compatible lens series, thus, AI compatible. Can be mounted without any problems.

- IX-series:
AP-S type, created for the low budget Nikon Pronea S. Can not be mounted because the bayonet is smaller than the standard F-Mount.
Moreover, even if it were somehow possible to mount them, their back-end tube is considerably longer than that of any other AI compatible lens, which means they would inevitably break the mirror of a modern SLR.
Marked “IX Nikkor”, they are mostly silver or silver/black polycarbonate (20-60mm, 24-70mm, 30-60mm and 60-180mm)

Disclaimer:
I have not done exhaustive research on each and every Nikon DSLR or Nikkor MF-lens available.
Yours may be the exception: do not risk mounting unidentified lenses on your camera and always consult your user’s manual: section Technical Notes > Compatible Lenses > Non-CPU lenses, to find out more about compatibility and usability.
To facilitate search, you may want to download your user’s manual in PDF from a Nikon web site, open the file in Acrobat or Reader and do a search for any of these terms.

Finally, and I cannot emphasize this enough: don't even think about mounting pre-AI, F-type (A, C, F, H & HC, K, N & NC, O, PD, Q & QD, S & SC, T, UD, Auto, etc.) lenses on your Nikon DSLR or you will be sorry, except if you are 100% sure that they have been AI-ed, that is, have their aperture ring modified to meet the AI spec.
AI-ing implies machining away parts of the aperture ring to only leave the so-called AI meter coupling ridge and the minimum aperture post, which is exactly why old, unmodified F-lenses will damage or break the meter coupling mechanisms on modern cameras: they have metal where there should be none.
For more on Pre-AI lenses and the F-Mount, click here

You might also want to read this:
The Nikon F-mount and manual focus NAI, AI, AI-S, AI-P, Series E and auto-focus AF-D, AF-I, AF-S, D- and G-Type lenses. A compatibility inventory