Cleaning clouded mirror Makinon 300mm f5.6

caerwall · Joined: 11 Nov 2010 Posts: 51

Loved the lens, but have not used it for years as the mirror surface went cloudy and images assumed a '"milky" appearance.

Unable to come in through the front element as it is surely very "stuck" I found a reference to removing the rubber grip - slide it forwards and remove the tape underneath - works with this lens and you can unscrew the front part and the helix - but this is not necessary to clean the mirror and also the helix is a big bother to get back together again. Spent a happy hour before it decided to re-thread without jamming.

The easy way is to remove the five screws holding the mount to the lens body. Not the the three screws that hold the silver metal mounting flange but the five in the outer rear part of the lens. They are quite hard to shift as they seemingly have been fixed with some sort of locking material.

Once removed you can access a large locking ring and remove it with a suitable spanner tool. There is a gasket underneath that comes off as well. The mirror element can be carefully removed along with the rear lens element. The mirror is a sandwiched piece of glass with the silvered surface inside well protected. Not like some of the horror stories that I have heard about front surfaced mirrors - "one touch and they are destroyed".

It is easier cleaning to remove the rear element as well - another locking ring and gasket and the mirror is free and unencumbered.

After making sure it was indeed glass that I was cleaning I just cleaned the scum off normally and polished the glass with a clean micro fibre cloth. Re-assembly is the usual reverse process. I had to re-assemble the front element and helix but if cleaning the mirror was the only task the only big issue is removing the first five locked down screws. This lens had a PK mount but I presume that other mounts are set up similarly.

Mirror is as shiny as new and that cloudy cast is well gone.

Not as hard as I had imagined.

TomC

Attila · Expire: 2025-11-18

Many thanks Tom for this guide!

pat donnelly · Posted: Thu Jun 30, 2011 4:32 am Post subject:

Thanks!

All part and parcel of liking manual focus lenses!

caerwall · Joined: 11 Nov 2010 Posts: 51

If you do decide to screw out the helix to re-lubricate it or anything else the locking tape has to be replaced with the focus ring in the right place. I thought I put it back correctly but found that infinity was at 15' on the scale.

Remove the tape, find infinity visually, with digital it is "a soda" in daylight. Make sure the loose scale reads infinity at the fixed mark as well and re-tape it correctly. Easy.

I was able to re-use the silvered tape but fresh tape might be required. Insulation tape might work but it has to hold the two sides of the lens sufficiently well to stop them unscrewing in regular use. Insulation tape might also degrade with heat, but I think it would work if carefully applied - once the rubber grip is replaced there should be less tendency to unscrew the halves when working focus.

Obviously this applies to the Makinon lens I worked on - but the construction is pretty simple really.

This lens had the mirror surface in a glass "sandwich" and protected. I have seen some warnings on the web advising not to directly clean an exposed mirror surface as it is EXTREMELY fragile and very easily damaged.

Lens is now working well (for a mirror lens) - all those years in a drawer - what a pity.