Autofocus does not work consistently

<p>I have a D200 and a small range of primes and zooms. I swap lenses quite a bit and my biggest frustration is that after swapping a lens, the autofocus may not work (on zoom, 3rd party zoom, and AF-D lenses) at all.</p>

<p>This can sometimes be fixed by turning off and on the camera repeatedly while trying to autofocus. Sometimes this can be fixed by detaching and reattaching the lens. I will usually </p>

<p>I have cleaned all the contacts on the camera and lens with a lens cloth but it doesn't seem to help. Is there anything else I can try before sending it in?</p>

<p>Out of curiosity, is the camera powered on, or off, when the lenses are being changed?</p>

<p>If this is occurring with "screwdriver" type autofocus Nikkors and third party lenses, is it possible the blade driven by the body and the mating slot in the lens haven't meshed? Out of habit, whenever I mount a mechanical linkage AF Nikkor or third party lens I always gently twist the lens focus ring until it mates with the driving blade on the body.</p>

<p>If it happens with all lenses, then it must be one of two things. Either the contacts on the camera are bad or you're not attaching the lenses properly.</p>

<p>Can you try mounting one of your lenses on a friend's Nikon to see whether it has the same problem?</p>

<p>@Matt: I try to change lenses with the camera off, but don't always remember to turn it off first.</p>

<p>@Lex: I have tried moving the focus ring until it clicks, and then auto-focusing but it doesn't help.</p>

<p>@Dan: I have mounted my lenses on a friend's camera and they work fine. Also, I doubt the same problem can occur across 5-6 of my lenses. :(</p>

<p>One thing I noticed about my D200 was that, because of how I grabbed the body with my left hand - often while about to change lenses - I sometimes nudged the M/S/C lever switch to a position slightly between two of those positions, making the camera stupid. I caught myself with this problem several times. Does this happen regardless of which position that switch is in?</p>

<p>I am having the same problem on my D90 with the 18/105 3.5vr and the 70/200 2.8 vr. The focus will be clear for an instant then will blur. I can touch the focus ring just a little and it will clear up. Cannot take a candid action photo because of this. I have cleaned contacts also.<br>

Bill</p>

<p>@Matt: That has happened before so I always check that now, but it still has the same AF issues after checking.</p>