lens reassembly (after cleaning)

[Neil Grant]

...obviously elements should go back where they came from but is it important to maintain their original position from a rotational point-of-view?

 

[Kino]

...obviously elements should go back where they came from but is it important to maintain their original position from a rotational point-of-view?

Not unless they are anamorphic or telecentric objectives. Of course, if you can do it, why not and be doubly sure...

 

[AgX]

Not unless they are anamorphic or telecentric objectives.

The elements in telecentric lenses are rotational-symmetric too.

 

[David Lyga]

Rotation does not matter: that part is homogeneous! But beware: make certain that they go back in the correct direction. This becomes especially difficult to do when you dare to dismantle anything wider than 28mm, Only then will you worship at the altar of lens manufacture when you see all those tiny optics tumble out of a 24mm lens! It is truly terrifying.

When reassembling, take each element and carefully wipe it in circular fashion, using a ultra soft tissue, with a few drops of window cleaner. This is preferred, even essential, as compared with alcohol because the alcohol will impart static and the window cleaner (even a drop of dish liquid in a little water will do) will negate that static, allowing dust to be blown away. Work carefully and remember that dust is everywhere and is an especially pernicious annoyance.

Beware of this!!! There are a few lenses out there (one of which is the next to rear element of the Minolta PF 1.4 / 58mm) which, if the element is rubbed even gently, will force scratches into its surface. I have one which has a multitude of circular marks because I was not aware of this 'rare earth' glass. This problem is really not too frequent, but it is there with some 'esoteric' optics. - David Lyga

 

[Neil Grant]

Rotation does not matter: that part is homogeneous! - yes i would have thought so. Anyway i marked the element with felt tip before removing it (so, the outer surface) and the inner barrel opposite as well (so i had two red marks). Carefully cleaned with isopropyl alcohol (without erasing the felt tip mark), soft brush and dropped back in with some tweezers gripping the element protected by a tiny bit of lens tissue. Fiddly because the 'seat' was a long way down the lens barrel.

 

[REAndy]

I setup a video camera (your phone will work too) to record the disassembly process. This can be invaluable information when reassembling. I have also disassembled a lens (or other things) inside a fish aquarium on its side. Helps to keep parts contained, and I like to think it also provides some dust protection.