Cleaning the internal optics of a Nikon Coolscan 5000ED film scanner.

  8 minute read  



Exposed optics in a Nikon Coolscan 5000ED
Exposed optics in a Nikon Coolscan 5000ED

One problem with the Nikon Coolscan scanners is that they tend to accumulate dust on their internal optics which can manifest itself as flare in the scans. The mirror in the optical path is especially prone to this as it sits at the front of the scanner, just below the front opening of the case. Dust can easily get in, fall under gravity and end up resting on this mirror surface. Just behind the mirror, under the scanning body, is a lens that directs the image onto the sensor, although this tends to attract less dirt than the mirror.

The Nikon Coolscan 5000ED is especially bad for this as it does not have a built-in cover for the front opening. Thus it is essential to always have a film adapter inserted into the scanner to obscure this opening. The MA-21 is a simple solution. My scanner normally has the SF-200 bulk slide adapter fitted when not in use.

Another tip is to keep the scanner sitting on its side, so that the film plane is vertical. This also keeps the mirror vertical reducing the chance that dust will settle on it. If enough dirt gets in then the mirror needs to be cleaned. Unfortunately this will require dismantling the scanner a little. A bit of a pain that requires some care to avoid damaging the mirror or the scanner.


Prepare a clean, well lit, work area.

I used:

  • Jeweller’s cross head screwdriver. I used a JIS 3.0mm screwdriver. Japanese equipment usually uses JIS crosshead screws and a normal Phillips or Posidrive screw driver can damage the screw head.
  • Jeweller’s flat head screwdriver.
  • A case to organise the screws that are removed from the scanner during the dismantling process.
  • Latex gloves (to keep the grease and oils of your hands away from the optics).
  • Giottos Rocket Blower. Used to blow dust of the mirror before cleaning.
  • Soft brush. Used to sweep dust off the mirror. I use a clean makeup brush.
  • Lens cleaning fluid.
  • Pec Pads. Non-abrasive tissues intended for cleaning delicate optical surfaces.
Scanner cleaning equipment

When doing repairs on complex equipment it pays to stay organised. These devices often have lots of different parts, secured with all types of fastenings, that need to be disassembled and reassembled correctly.

I would recommend having a tray with lots of compartments for holding screws and fastenings from each step of the disassembly. I marked each compartment with a number showing the order of the various steps the parts placed in that compartment come from.

Storage container for screws

I next recommend you take a picture of each stage of the disassembly process. Take a picture before conducting the step, and then another picture afterwards. This helps in the reassembly as you can reverse the steps you made during disassembly and see what part fits where.


Step 1: Remove Outer Case

Unplug the scanner and remove the mains and USB cables. Remove any film adapter. Place the scanner upside down on a clean work surface.

Scanner placed upside down

Remove the 6 screws on the back panel that secure the cover to the scanner.

Step 1 Disassembly

Pull out the 4 rubber pads that act as feet to the scanner. These pads cover additional screws that secure the cover. Remove these 4 screws.

Step 2 Disassembly

Slide the cover backward away from the front panel of the scanner, and then remove it. Alternatively, you can push the back plate forward to slide the scanner internals out from the cover. Make sure the scanner internals are resting upside down at the end of this step.

Scanner without cover

Step 2: Remove Mirror

Once you have access to the internals of the scanner. you need to move the scan head backwards to improve access to the mirror box. The movement of the scan head is controlled by a worm gear driven by a large white plastic gear at the front.

Scanner head in forward position

Rotate this white plastic gear to move the scan head all the way back.

Scanner head in backward position

Once the scan head is all the way back, you can see the mirror box. The mirror is fixed in place by a little clip. Using a jeweller’s flat screwdriver prise one of the bottom fingers of this clip forward to release it from the mirror box.

Remove first mirror clip finger

Then prise of the second finger of the clip.

Remove second mirror clip finger

Remove the clip. Lift it upwards and it should be easy to extract it. So long as the scanner was placed on the work surface upside down the mirror should remain in place inside the mirror box.

Mirror clip

The mirror is now free to be removed. As the mirror is silvered on the front surface it is very delicate and easily scratched. The reflecting surface of the mirror will be facing down at this point (it is the side away from where the retaining clip held the mirror).

Wear latex gloves at this point to avoid getting grease and oil from your hands on the mirror. Try and touch the mirror only by its sides, not the front surface. Lift the mirror up from its position in the mirror box until it is standing vertically. Then tease it up and sideways out of the scanner with the fingertips from both hands.

Removing the mirror from the scanner

When out of the mirror box you should be able to grasp the edges with two fingers from one hand and be able to lay the mirror on a clean non-abrasive surface, such as a fresh Pec Pad, with its silvered surface facing up.

Mirror removed from scanner and placed on Pec Pad

Step 3: Clean The Mirror

When I cleaned this scanner the mirror had little dust, but a couple of spots of light haze on it. This is almost impossible to capture in a photograph.

Dirty mirror

When cleaning the mirror you need to be very careful not to scratch the surface by dragging grit across it. I aim to remove the as much grit as I can using light actions, before trying to remove any dirt stains. Try and use clean materials each time you touch the mirror surface.

The first step is to blow some air over the surface with a Giottos rocket blower to dislodge any loose dust.

Blowing dust off the mirror

I then give the surface some light sweeps from a soft brush, like a new makeup brush.

Brushing dust off the mirror

Next, I take a fresh Pec Pad and spray a little lens cleaning fluid onto the pad.

Spraying lens cleaning fluid onto a Pec Pad

I then wipe this damp centre portion of the pad lightly across the mirror surface to remove most of any remaining dust.

Wiping the mirror clean with a Pec Pad

Hopefully the mirror is dust free at this point. I then take another fresh PecPad. Again a spray a little lens cleaning fluid on its surface. I then give the mirror surface some swipes covering the whole surface. I try and make sure each time I do a new swipe I use a fresh portion of the pad. Finally I try and dry the mirror by swiping it with part of the pad that were not wetted by the cleaning fluid.

Hopefully, by the end of this process you have a spotlessly clean mirror. If not, you can repeat the process with fresh PecPads. The aim is to be gentle, you can always repeat the action again. The main thing is to not drag dirt across the surface.

Cleaned mirror

Step 4: Clean the Scanner Lens

Good luck with that.

Even with the mirror out the front surface of the scanner optics is very hard to see, never mind clean. I think you would have to disassemble the scanner much more to gain access to this part outside the adapter frame.

Fortunately the scanner optics don’t tend to get anywhere near as dirty as the mirror as they sit vertically. If the mirror was not too filthy it may be sufficient to give the front element a few puffs with the rocket blower whilst the mirror is out.

Step 5: Insert The Mirror

Pick up the mirror from the cleaning surface by using the mirror edges only. You should be able to reverse the actions of taking the mirror out. Bring the mirror to the scanner with the silvered surface facing towards the rear of the scanner. Then using fingers from two hands, one positioned through the scanner gap, position the mirror back into the mirror box standing vertically. Finally, with a fingertip, you should be able to tilt the mirror back down into its diagonal resting position.

Mirror re-inserted into mirror box

Next refit the retaining clip. Essentially place it so that you can slide it down the front edge of the mirror box, with the fingers to the outside. Get it roughly in position at first so the the front edge of the mirror box is slipping into the slot in the clip.

Mirror clip being re-inserted into mirror box

Make sure the clip is centred and it should easily slide down until the retaining fingers overlap the bottom of the mirror box and can spring back into position.

Mirror clip back in position in the mirror box

Step 6: Close Up The Case

Replace the scanner cover. I found it easiest to place the cover standing vertically on my work surface, with the end without the flange for the retaining screws facing upwards. I could then lower the scanner internals into the cover, rear facing down. Once the edges are all located it should be easy to slide the scanner internals down into the cover.

Now replace the 4 screws that fit under the rubber feet. To this I placed the scanner on the worktop upside down. I then had to apply a little pressure to slide the cover forward, and align the screw holes, as I put each screw back in. I just made them loosely snug at this point.

Now replace the 6 screws that secure the back of the scanner cover to the backplate of the scanner. Again I make each screw only loosely snug at first until they are all in. Then I go around all 10 screws to give them their final tightening.

Finally squeeze the rubber feet back into position in their retaining slots.