Cleaning Optics of a Micro-Nikkor 105mm f/2.8 AF-D

The 105mm macro lens has its origins in the 1960s and 1970s with the legendary 55mm macros and eventually deliverying its 105mm f/4 and f/2.8 variations from the lates 1970s into the mid 1980s . As with lenses of that era they were only capable of 1:2 reproduction ratio, even with the 1984 105mm f/2.8 AI-S. Work on the AF macro lens started in 1987 with full redesign (including optical rework) completed and release in 1990 with a priority to support autofocus and push the maximum reproduction ratio from 1:2 up to 1:1 (life-size) and eventually in 1993 the AF-D was released, with changes for the distance encoder

As with many old lenses cleaning of the optics might be necessary and the following appears to be only source to document front, middle and rear elements.

Optics

The optics consist of 9 elements in 8 groups and housed in 4 logical blocks.



To service all optics, work with the front and middle logical blocks before going to the rear.

Front Optics Only

• Ensure lens is not limited and then remove the front collar
  
  
  
  
  
  
  
  
• With the lens a MFD, use a rubber tool or spanner (slots visslbe now) to unseat the front element logical block of 3 elements
  
  
  
  
  
  
• This block of 3 elements seem to be a sealed unit - I didn't need to explore futher as I only needed access to the rear of this block for cleaning

Front and Middle Optics

If you need full access to the middle block of optics (elements 4,5 and 6) behind the aperture mechansim you will have to remove them from the front. They do not come out from the rear and when you remove them this block is again a sealed unit.

• As above, strip off the front collars but you do NOT need to remove the optical block. We need access to the nylon rollers at MFD
  
  
  ^{ignore that the focus ring has been removed}
  
  
• Remove the next retaining collar
  
  
  
  
• Remove the 6x (2x sets) nylon rollers and pull forward the housing for the front logical block AND the aperture mechanism. Screwed onto the rear of the aperture mechanism is the middle logical block as a seal unit.
  
  Unscrewing the middle optical block needs some torque and you have to be careful of the aperture actuation lever - I use a long plumbers's grip and rubber to grip the optical block to easily twist after applying accetone.
  
  
  
  
  
  

Rear Optics

This is a little complicated and the elements are in 2 housings that require the removal of the rear mount and aperture ring. With being an AF-D lens with CPU contacts you need to be very careful to avoid damage. Annoyingly you have to pay attention to the length of the screws in certain places as they are not all the same - the black screw on the mount seems identical as the other longer screws but best to put this back where it was originally.

• Remove the screws on the CPU block and then the baffle
  
  
  ^{ignore that the rear mount screws are gone - do not remove those screws to give you more stability}
  
  Note the short screw location for the rear baffle
  
  
  
• Remove the rear mount
  
  
  
  Note the location of the shorter screw
  
  
  
  When lifting the mount take care of the long aperture lever.
  
  
  
  
• Lift the aperture ring and note the structure - the ring sits as 2x peices with one that moves the aperture and one that locks aperture/captures the screw drive
  
  
  
  
  
  
  
  There is a brass ring that sits over the aperture tab which sits in a grover between 2 chrome posts. Take note to ensure the brass ring aligns correctly when reassembling but it only sits one place over the chrome posts.
  
  
  
  
• Remove the rear (9th) element - the slots are right up against the wall so you need a straight edge spanner and be careful of the flex cable for the CPU block. You could remove the brass ring that holds the flex cable to give yourself a bit more space if required.
  
  
  
  
  
  As you can see the rear element is not removable from its housing and can be challenging to clean the inside edges of the lens element.
  
  
• Remove the 7th and 8th elements - the spanner slots are in a better position for this housing.
  
  
  
  
  
  Again, this 2x elements appear to be in a sealed unit but I didn't explore futher since I only needed access to the face of the 7th element.
  
  
• A viewing to the rear of the milddle block and the rear of the 6th element.
  
  
  
  You could try tro clean this from this position but it sits a little deep so anything other than a blower is risky. The middle block does NOT exit from the rear, you have to go from the front.
  

Reassembly Gotchas

The nylon rollers can be difficult to sit especially since the housing itself is not snug in the barrel so float and you need to support the housing whilst trying to catch the screw holes.

On the rear, seating the screw drive and the aperture ring assembly can be fiddly - I reassembled with the aperture ring in two, first the aperture lock with the shaft of the screw drive and then the aperture ring assembly on top to ensure it catches the aperture tab.

For the rear mount align the screw drive hole correctly and engage the stop down actuation tab so that its under tension as you seat it - I've had the spring unhook otherwise. With the lens as below, the aperture lever goes the LEFT of the aperture activation lever



Kenneth Olsen has a video that shows disassembly of the lens to address a focusing issue - whilst it gives you a view of the lens and in particular the removal of the rear mount, its not helpful for servicing the optics.