Odd results with old AF 35-70 3.3-4.5 on newer body

<p>I just got back from an easter camping trip in the mountains. Before leaving I decided to take a lens and camera combo I didn´t need to be too worried about getting thrown around in the tent or getting wet in the snow etc... I was only going to be shooting holiday snap-shots so I wasn´t too concerned about the quality of the pictures. So I put an old cheap 35-70mm 3.3-4.5 AF on my D3s and went about taking pictures. Before long I noticed that the lens was overexposing as I increased the f-number.<br /> The aperture ring was locked on f22 and in the display everything appeared normal. The aperture number increased as I rotated the sub command dial and the shutter speed subsequently decreased. I was shooting in A mode with matrix metering. There was no exposure compensation applied. The combination of shutter speed and aperture displayed should have given a correct exposure, but it didn´t. <br /> This led me to believe that the aperture was in fact not changing as the shot was taken, although it was changing if I pressed the preview button. Pictures taken at the max aperture of 3.3-4.5 were always correctly exposed, but by the time I reached f11 the overexposure was just horrible. At f22 the picture was almost completely white. <br /><br />Puzzled by the fact that the aperture wasn´t physically changing I began exploring solutions to the problem. I found that I was able to get the correct aperture if I did any of the following...</p>

<ol>

<li>shot in Mup mode</li>

<li>activated exposure delay</li>

<li>locked focus, pressed the preview button and fired a shot</li>

</ol>

<p>This in turn got me thinking that maybe the aperture lever in the camera wasn´t closing the aperture blades fast enough, so I took a picture of a dark scene, where the shutter speed fell to around 1/3 of a second for an aperture of f16. Guess what? I got a correctly exposed picture! <br /> Anyone else ever experience something like this? I know most people don´t bother putting cheap old lenses on their newer cameras, but maybe someone has tried?<br /> I tested the lens on a D300 and a D800 when I got home and the results were the same, so I was able to rule out the D3s as the problem. I should add that the aperture lever on the lens appears to be working normally and is not abnormally stiff. So what am I doing wrong? Surely the camera should stop down the lens before the shot is taken, regardless of the shutter speed?</p>

<p>You can remove the lens from the camera and play around with the mechanical lever on the rear end to see whether it opens and closes the aperture diaphragm smoothly, or maybe it is semi sticky and opens too slowly.</p>

<p>Since you have a D3, in live view, you can change the aperture on the lens and you should see the effect changes, e.g. the depth of field changes.</p>

<p>Possibly sluggish aperture blades due to oil or other debris. The lens may need a CLA.</p>

<p>Seems you are both right. At first glance the aperture diaphragm seems to open and close perfectly when I move the lever up and down, although there is a tiny delay, or stickyness, in the closing of the blades when I let go from fully open. It´s only just noticable, but would indeed be enough of a lag to effect the exposure. I saw it more clearly when I compared it to a newer lens. <br /><br />Thanks for your help. </p>