When you’ve spent a lot of time with a certain camera or lens, you sort of develop a relationship with it. You become familiar with its sharpness, field-of-view, and contrast, and know when to use it for taking the best images.
But, over time, technology changes, and camera bodies have become more intelligent. Since your old favorite lenses can’t electronically communicate with the new bodies, they might have been sadly relegated to the bag in the back of the closet. Surely, you didn’t sell any of your old faithful AI-S Nikkors, did you?
Assorted AI-S lenses
There are several older autofocus-capable Nikon film bodies that will fully or partially meter using non-CPU lenses (non-CPU = no electronic chip in lens). Many of the newer Nikon film and digital bodies won't. Instead they will disable the light meter, and turn our expensive computerized cameras into completely manual models as soon as a non-CPU lens is mounted.
The reason Nikon chose to do this is simple. A non-CPU lens has no microchip inside to inform the camera body of lens settings. If you’ll notice, many of our newer AF lenses have no mechanical coupling to engage the camera body aperture control ring. In fact, many of our new lenses (G-Type) do not even have an aperture dial. Instead, the aperture and shutter speed functions are controlled by the command dials. On most of the newer Nikons, the aperture control ring is not even there any more.
RETURN OF THE RING (or THE RING OF POWER)
Ignoring my lame Tolkien references above, look at figure 1. Notice the aperture control ring on my old Nikon FE (circa mid-1980s), and the connector notch on the lens. How long has it been since you thought about this old mechanical feature? Until I wrote this article, I didn’t even notice that it was missing on the newer camera bodies. I checked my D100 and D70, but it’s just not there!
Now, in comparison, look at the D2x aperture control ring below. It looks very similar to the one found on the old Nikon FE above. It is clear that the D2x is prepared to mount AI-S Lenses.
Since the aperture ring remains on the D2x, D2h, and F6 cameras, they can tell when we change the aperture on an old non-CPU lens.
But, the old lens has no micro chip inside to tell what the maximum aperture is. And without the CPU chip, the camera doesn’t know what the focal length of the lens is, either.
So, the cameras have a relatively simple means to let their bodies know those values. You use the FUNC button on the front of the D2x, and the command dials, to inform the D2x of maximum aperture and focal length. It only takes a few seconds, and allows the D2x to use Matrix Metering with your old faithful non-CPU Nikkors.
This article is written from the perspective of the D2x, but virtually all of this information also applies to the D2h and F6.
Why not get your D2x, an old favorite AI or AI-S Nikkor lens, and your D2x manual, and let’s examine how this works. It’s a lot easier than the manual makes it look!
The procedures below work best on single focal length lenses, or zooms with a constant aperture across the zoom range. You can use zoom lenses with variable apertures, but there are some minor difficulties which we will discuss later. On pages 128-131 of the D2x manual, you’ll find detailed information on these procedures. Also, pages 3-5 of the manual shows the names and locations of the various controls used in Method Two below.
There are two ways to set the lens specifications. We’ll consider the two methods next.