D300 "Crashes" with Manual Lenses?

<p>I have today experienced a repeat of a problem my D300 has had in the past with manual focus lenses. I like to use a 105mm f/2.5 AI and a 50mm f/1.4AI Nikkor with my D300. I shoot in the studio on Manual with off-camera strobes. All of a sudden, in the middle of a shoot, the lens will fail to stop down when I expose my shot. This gives me a frame that is about (usually) five stops or so overexposed. It repeats this problem frame after frame.<br>

The first time I had no idea what to do and after my shoot I called Nikon. They told me to do the "reset" thing with the green buttons and that seemed to fix the problem. It did the same thing today, with my 105mm and then my 50mm and resetting it did not fix the problem. I put my 18-70 Autofocus Nikkor lens on it and everything was fine but WHY did the body fail to stop down my other lenses? I have them both properly programmed into the camera body as "Non-CPU Lenses" and they work fine 99.9% of the time. Then this!<br>

Is this a known issue? Can anyone help me out?<br>

Thanks-</p>

<p>Peter</p>

<p>Peter,<br />Are you sure its the camera ? It could be the lenses too maybe ?<br />Did you check the lenses for "sticky Blades" ? <br />( check the working of the aperture blades by gently operating the aperture lever of the lenses and let go a few times .).</p>

<p>Try to assign F-n button to one of the non-CPU lens and see if that solves the problem ? If it works, assign the second lens the same way, and use the Main command dial to select one lens or another to match the mounted lens.</p>

<p> </p>

<p>I would personally check the lenses on another body if you have an old Nikon sitting around. If they work fine, then you know it has to be your D300 body.</p>

<p>Does the lens stop down when you press the DOF-preview button?</p>

<p>I use MF AiS lenses all the time on a D700 and have never once had this problem. Even using the "wrong" non-cpu lens setting (i.e. a different maximum aperture) doesn't cause any problem, just incorrect EXIF data. Nor do using non-Nikkor or Ai converted lenses.</p>

<p>It definitely sounds like a camera fault, since it's unlikely that 2 different Nikkors would produce the same issue. Sticky blades will overexpose, but usually consistently and not suddenly halfway through a shoot, only to then miraculously cure themselves a short while later. Also the two lenses you're using aren't "blacklisted" as being known to have aperture blade problems.</p>

<p>Double check for sticky apertures by pressing the DOF preview before releasing the shutter and as mentioned above try testing the aperture action. Set the lens to its minimum aperture and "flick" the lever with your thumb so it closes and opens as fast as possible. You should still be able to make out the iris closing fully when you look through the lens. A sticky lens won't be able to close fast enough for this to happen.</p>

<p>However I suspect that for some reason your camera suddenly thinks it's got a G-type lens attached and only tries to stop down electrically. I think it might be time to get Nikon's repair bods involved - and good luck with that!</p>

<p>Thank you, one and all. Now I've got some new things to try out in my effort to solve the problem.</p>