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I got the error pretty consistently 1 month after getting my D90,
usually when first turned on. It was pretty obvious what it was, a
slight rotation or the 18-105VR lens cleared it immediately. It never
happened with my 50mm or 70-200VR f/2.8
I simply removed the lens and applied a very thin coating of D-5
De-Oxit deoxdizing chemical to the lens spring loaded contacts. D-5
is available at any electronics supply store or some hi-fi stores.
Exposed contacts are likely to pick up dirt or a layer of oxidation
after contact with atmospheric oxygen.
DO NOT us contact "cleaner" or DW-40, common substitutes used for
oxidation that will in fact make any switch or contact much worse and
eventually ruin the device. The chemicals sold as contact cleaners
like the Radio Shack contact cleaner are fine for cleaning oils and
grease from small parts but do nothing to breakup the very thin layer
of oxidation that forms anytime metals are exposed to air. Normally a
few molecules of surface metals will combine with the oxygen to form
an oxide of that metal which is an insulator that does not conduct
electron flow. The layer of oxide is normal and in normal thickness
of 2-6 molecules is easily jumped over by normal voltages used in
electronic devices. The oxide layer actually is desired to prevent
further, deeper oxidation that would require higher voltages to
overcome the barrier. Some metals resist oxide formation, such as the
gold contacts on the D90-lens contacts. But gold is not used in pure
form, but an alloy that has other metals that give it hardness also
makes it subject to oxidation just like other metals. Some metals
depend on oxide for protection because their surface is so reactive,
such as copper and aluminium that they are intentionally oxidizes
when formed.
The problem with normal contact cleaners is that they are overly dry,
cleaning exposes the metal to rapid and deeper oxidation. It will
work sometimes but after a few minutes the problem with contacts will
be worse than ever or permanent.
That is why a special deoxidizing chemical has oxide removing
properties but also a wetting agent that covers and adheres to the
metal surface that prevents any direct oxygen penetration and oxide
build up.
It comes in a liquid or spray form. If spray is what you find, do not
spray the D-5 chemical onto any part of your camera or lens. Spray a
little in the plastic cap for the can and wet a Q-tip and use that
to paint a very thing layer of the D-5 on the contacts of the lens
and camera. It can be used immediately afterwards.
The contact problem is NOT a D90 or Nikon problem, it is normal for
contacts to sometimes build up resistance to the flow of electricity
after exposure to dirt or oxygen. If you ever hear a scratchy sound
coming from speakers when a volume or tone control rotated on a
stereo, you are hearing this same effect and a tiny amount of D-r or
other deoxident will take care of the problem immediately.
Exchanging the camera might not take care of it if the oxide is on
the lens....or simply rocking the contacts back and forth a couple
times when mounting the lens or removing the lens once in a while and
reinstalling it will self clean the contacts to make it go away for a
month or two. It went away on mine after I bought other lenses and
occasionally mounted those, although 80% of the time I have the
general purpose kit lens mounted.
