Lens surgery

I’ve not been having the best luck with my lenses recently.

I’ve just got my beastly 80-200mm f2.8 lens back from the repair shop after it had an outbreak of lens fungus deep within the glass elements of the lens that I noticed after spending a wet few hours on the Isle of Staffa chasing Puffins. The stripping, cleaning and rebuilding cost about £100, but the lens is easily worth 6 times that so it was not too much of a shock. Plus I did get some great Puffin images which is something i’d been wanting to do for ages.

d300_3

That was all well and good and sorted. But now I have noticed oil on the aperture blades within my favorite 35mm f2.0 lens that I’ve been using on my Nikon FE a lot recently.

This is bad for two reasons. Firstly the aperture blades are so thin and delicate that a small amount of oil between the individual blades creates drag between them and slows the response of the aperture down, threatening your correct exposures in the short term and potentially jamming completely in the longer term. Secondly the oil could eventually transfer onto the glass elements either side of the aperture, causing a loss of sharpness and requiring a proper clean.

So, as any sensible person does these days, I found an internet forum post explaining how to take the lens apart and clean the aperture blades and i fetched my screwdrivers!

The aperture unit is buried within the middle of the lens so i took a deep breath and proceed to remove the back of the lens casing. One then has to negotiate the aperture ring and coupling system and the innards of the autofocus mechanism, but these things are well made and of sufficient age to have been designed with maintenance in mind so they pull out of the way without any annoyingly easy to break plastic clips of the kind of springs you need a 10 tonne press to push back into place. The rear three glass elements can then be removed from the lens through a combination of unscrewing and (delicately!) prying out with a small screwdriver.

All of this exposes the aperture blades themselves, which were stuck partially open as the oil (visible as shiny smears on the blades) is creating enough friction to overcome the spring that parks the blades in the closed position normally.

It took about an hour and a big pile of cotton buds and some isopropyl alcohol to dissolve and remove the oil to get the thing looking better and the mechanism moving more freely. There is a risk to doing anything like this, but I am of the opinion that these things are not designed and built by wizards so there is always a basic mechanical logic to follow when stripping, repairing and reassembling them.

After reassembling (twice, as after the first attempt I realised why they build these things in clean rooms to keep the dust out) it all still seams to be working fine again. Which is good as I now have another new Nikon body to run a test roll through.

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