Rear End Cleaning: 85mm f/1.4D

Oh dear.. Whilst I don't care too much about dust on internal lens elements, I do care about the dreaded 'f' word.

Look again at the object on the rear element near the 4 lens contacts - I noticed this whilst changing lenses recently. At first I didn't pay much attention to it even though it was a new foriegn object on the inside of the rear element - all lenses of all grades (even top of the line pro lenses) get dust sucked into them at some point.

But after a little while I took another look at how such a big foreign object could just suddenly appear - I knew of the other dust and other objects (see top right of frame) but this was new. And large. On closer inspection I still wasn't sure what it was. Could it be the dread 'f'?
^{100% zoom of Nikon AF-D rear element taken with micro-Nikkor}

I didn't think it could be fungus but it looked like a very odd shaped dust particle. Could it be some frabric or something else. My lenses are stored with large packets of silica gell and in a non humid location so I hoped it was just dust. But what if it wasn't...

So what to do? I read many places online that people cleaned fungus using various potions: ammonia, hydrogen peroxide, distilled white vinegar.. it started to weigh on my mind as this was the rear of my favourite and most used lens. All that I read stated that once the 'f' sets in then no matter how well you clean it's bound to return.


The first step I want to try was to blow off this particle to avoid any "setting in" just incase it was fungus starting to grow. But that meant removing the rear element. A couple of sources (Lens Rental and Photography Life) had tutorials for cleaning dusty rear elements - these of course come along with very clear disclaimers.

I had nothing to lose (wait on have a lens potentially destroyed by fungus!) I thought and the removal of the Nikon AF-D rear elements appear to be fairly easy - removal of 3x large screws (not the smaller ones securing the CPU contacts) and the rear element pops out. And that's exactly what I did with an optician's screwdriver. A few rocket blower puffs later, with the rear element far away from any lenses, and all was clear.

Right now I'm still not sure whether this foreign object was just textile fibre or fungus or what but at least it's no longer sitting on the rear element, potentially growing. If the 'f' does return, I will know that this lens will have to go for professional clean but lets hope it's not going down that way.


For those a that are a little more comfortable with disassembling their lenses further: