Gear Talk > What the Nerds Do
Chipping a Nikkor - A Walk-through
Bjørn Rørslett:
It is worth noting that most medium or longer focal length lenses don't need the cut-out in the bayonet mount itself. The case of the 18 mm exemplifies the typical shape of the bayonet for Nikkors such as 20, 24, 28 mm etc. These shorter lenses also requires a short (5-pin) contact block from an AF/AFD/IX-Nikkor or third-party lens, whilst most other lenses are well served by any long block (7-10 pins; of which only 5 are used) found on AFS lenses.
A cut-out of the rear light baffle, on the other hand, always is necessary, otherwise there will be no space in which to seat the contact block.
The typical layout of the CPU print is the "L" shape shown in this walk-through example. The "L" is a general-purpose form factor that can be used with most lenses. There are other specialised shapes as well, and they can facilitate the modification of some otherwise tricky lenses. The 35/1.4, 16/3.5, and 85/1.4, to name some, can only be modified with CPU print with alternate print layouts.
The time necessary for the modification ranges from 15 minutes for the easiest ones to a whole work day for the really difficult challenges.
Bjørn Rørslett:
In answer to the following
" I am just curious how would this chipping allow the dial on the camera to set the aperture? "
It does, believe me. The technical explanation is rather long, so I'll skip it. But there is no magic involved.
You can also realise this is happening since the "P" and "S" modes are available and fully functional; they both work by changing the actual aperture on the lens.
The CPU chips can be programmed to work both in "P" ( the AI-P designation originally used by Nikon for 45/2.8, 500/4, and 1200-1700/5.6-8) or "G" mode, which encompass virtually all AF lenses made the last 30 years. All AF and AFS lenses also are AI-S, meaning they have a linear aperture mechanism. To complicate the matter further, Ai-P are also Ai-S. Nikon never made their nomenclature crystalline clear. The problem is mainly the earlier classes of lenses, pre-AI (before 1977) or AI (1977-ca. 1981). The pre-AI class can be converted to AI (often designated AI'd) so I treat both under the AI category.
Initially, there is no difference as both kinds will allow the aperture to be set from the camera side and on the surface, all exposure programs (A, M, S, P) will be functional if a CPU is added to them. However, although the read-out metering value is correct in both cases, the actual exposure can differ substantially. This is because the camera calculates the amount to stop down the lens (actually, the travel of the stop-down plunger inside the camera) based on a linear model, but the aperture movement of the AI/AI-modied Nikkors is non-linear. So for example, the meter reading says f/8, 1/250 (and these are the settings you get with an AIS lens), the actual settings at the time of the exposure might be f/11, 1/250 for the AI due to the non-linearity. Thus, one easily gets underexposure with the AI kind.
However, if the aperture is set directly on the lens, using the aperture ring, both meter reading and the actual exposure will coincide, and there is no difference between AI/AI'd or AIS lenses.
The contact block acts as a control interface and simply relays the electric signals from the CPU print. In addition, there is the CPU, that does the real stuff.
If you employ a factory CPU unit scavenged from a broken lens, its signature cannot be changed. In some cases, using a unit from a zoom lens, you can fake a lens signature by short-circuiting the section that reports the focal length as this will alter the maximum aperture sent to the camera. However, such factory prints are large and bulky and very few lenses have the required space to host them. The customised CPUs shown in this thread are always the better and easier approach.
richardHaw:
Hello, is this the daisy chip that I have been reading a lot about? Thanks!
Bjørn Rørslett:
Naah. You are thinking of the 'Dandelion' chip that is a low quality product and quite likely to get damaged in use. (Seen some of those failures over the years).
My CPU chips are custom made and hand assembled. Each is carefully tested before shipping. They are programmed to the exact specifications of the hosting lens, and that includes EXIF showing the correct zooming range for a zoom lens. Depending on the actual lens to be used with, I program them either as "P" or "G" mode of operation. I recommend they be mounted with factory contact blocks so as to provide maximum reliability and robustness.
richardHaw:
--- Quote from: Bjørn Rørslett on February 05, 2016, 08:33:55 ---Naah. You are thinking of the 'Dandelion' chip that is a low quality product and quite likely to get damaged in use. (Seen some of those failures over the years).
My CPU chips are custom made and hand assembled. Each is carefully tested before shipping. They are programmed to the exact specifications of the hosting lens, and that includes EXIF showing the correct zooming range for a zoom lens. Depending on the actual lens to be used with, I program them either as "P" or "G" mode of operation. I recommend they be mounted with factory contact blocks so as to provide maximum reliability and robustness.
--- End quote ---
Thank you! i have always wanted to chip some of my lenses but i just cannot source cheap ones here in Japan :o :o :o
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