CPU-modification of Nikkors : Which Lenses Can be Upgraded?

By Bjørn Rørslett

During the autumn of 2002, I began a project aiming to modify a large number of my manual-focus Nikkor lenses. By inserting a matrix chip print into such lenses, they could be made compatible with all of my modern Nikon cameras. Rolland Elliott has offered such a service for several years, but won't upgrade all lenses and doesn't do bellows or extension tubes.

Be aware that Nikon officially won't recognize the potential of upgrading older lenses. This may be interpreted to mean they are more interested in selling you new AF lenses, than trying to make the most of your existing ones. Not an entirely surprising attitude, perhaps, but still an annoying and not commendable position.

Benefits achieved by upgrading MF lenses are several. You get matrix metering with all Nikon cameras supporting this metering method by electronic means, and colour metering is possible with F5 and D1-series cameras. Programmed operation modes (P, S) are available for people desperately in need of those short-cuts. You can set apertures by the command wheels on the camera, thus allowing manual lenses to operate with fully functional metering on F80/N80, D100, or similar models which Nikon has crippled. This is possible because Nikkor lenses have no linkage between the aperture control and the lens electronics, the steering of the aperture stopping down is entirely performed by the camera and depends on the camera being told some crucial data about the lens. Here the matrix CPU chip implanted in the lens comes into play. As long as it fakes the necessary data and communicates the needed information to the camera, the camera itself doesn't understand it has been tricked. The EXIF header in the image files will show data from the chip, not those of the lens in which the chip has been inserted, if case you wondered - any miracle has inherent limits. The aperture value will be correct, however.

To get maximum metering accuracy, apertures should be set directly on the lens. All my cameras are programmed this way if they support the feature. This is in fact always necessary for converted AI or non-AI lenses, and won't do any harm for AIS lenses either if your camera allows the aperture setting to be made in this manner (with F5, the camera will meter correctly, but aperture values are not displayed). If converted lenses are deployed on a D100, you have to control aperture from the camera itself and only using AIS lenses is recommended in this situation.

Modification of an older Nikkor lens is not very difficult in many cases, but you do have to drill holes in the lens mount and sometimes disassemble the lens completely or partially. Only recommended for the truly brave of heart amongst Nikon aficionados. You are warned. A local repairshop might be persuaded into doing the job in case you don't feel up to the task.

I have amassed data on the upgrade potential for a large number of Nikkor lenses, which are compiled in the following tables. I don't do upgrades for other people on a routine basis, so the list aims only to showing the huge potential that exists and I'll add more lenses along the road. For details about modifying special lenses or extension tubes, see the relevant articles found in my Review area.

* A maximum aperture of f/2.5 needs a custom-programmed chip. You
can replace this with a suitable f/2.8 chip, but then an exposure correction
needs to be set on the camera.

** Using a custom-programmed chip set to indicate "800/8 Ai-P".

*** Since this lens has a fixed aperture, any chip can be employed to give in-camera metering
(issues exist if a hand-held external meter is used). Or, a custom-programmed chip
specifying "1000/11 Ai-G" and with a single aperture setting of f/11 can be used.

**** Needs a custom-programmed chip so you can get the readings to encompass the range f/11-f/32.

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A number of Nikon bellows units can be modified as well. This would make the units much more versatile with all newer Nikon cameras. So far, I have converted my PB-4 Bellows, a small Novoflex bellows, and the Nikon Multiphot photomacrographic stand. An alternative is just chip-updating a narrow extension ring and insert it between the camera and bellows. Stop-down metering is the norm for bellows-based photography so any CPU-chip of a suitable size would be eligible for the update, you don't need to match the maximum aperture. The chip for the 45 mm f/2.8 AI-P Nikkor is perfect for such purposes. Even better is programming a "G"-type chip because you can dial in the actual aperture setting of the lens.

Recently, I have had access to a [limited] supply of programmable chips. These are much smaller than the original Nikon and can be programmed to specification with regard to focal length and aperture setting (to 1/6 of a stop, so f/1.1 or f/2.9 or similar "exotic" values are feasible). For a zoom lens you can specify the end points of the focal range, It was interesting to note that all Nikons could display apertures such as f/1.0, f/1.1, f/1.2, or for that matter, f/95, even though no CPU-enabled Nikkor lens has been made with such values. Unfortunately, the EXIF standard limits aperture to f/1 or smaller, so I can't give my f/0.75 lenses this value (but f/75 is OK). Another point worth mentioning is that all Nikkor CPUs inform the camera of the position of the exit pupil, and for a zoom lens, this data can change signficantly along the zooming range.