Pentax ME super underexposing (my fault?)

<p>Hi everyone!</p>

<p>I recently came across a nice Pentax ME Super body in and exchanged it for one of my Zenits at the local camera fair. It is in great condition with light seals recently replaced and i wanted to get into the PK system for lightness and to check out the lenses. I ordered a 1.7/50 and a Sigma mini-wide to go with it. However, i must have done some damage to it when cleaning it because it now greatly underexposes. Let me explain: While i was waiting for the lenses to arrive i noticed some sticky foam material between the mirror and the focusing screen where a band of fabric is. As it was clearly ready to peel off i gently removed it. Today the Sigma arrived and after fitting it to the camera i noticed serious underexposing (2.8 directly into the sun, the camera chose a slow 1/250 with ASA set to 400) which persisted after removing the lens. Removing this thin foam stripe must have moved some of the sticky goo onto the light sensors or there must be some light leak into the mirrorbox causing the camera to underexpose. Any help would be great. I'll upload a picture of the mirrorbox as it is now so you can have an idea. </p><div></div>

<p>Update: The meter has come back to normal, apparently remnants of goo were blocking the other two sensors at the corner. Without lens on, looking straight at the sun drives the speed to above 2000 (blinking) and in darkness it goes beyond 4 s with plausible values inbetween, depending on available light. HOWEVER, the underexposing still remains with the Sigma mini wide on the camera. Changing the aperture does not affect shutter speeds as the best i can get is a slow 1/250 in bright sunlight and 1-2s when pointing at the ceiling lamp, both at 2.8, staying there despite any changes to the aperture. I am not familiar with the Pentax bayonet, but it seems to me the small lever in the groove (green arrow) should be the one telling the camera what the aperture is, and extent of its movement should be according to the aperture when the other lever (magenta) is moved when the shutter fires. With the tall (magenta) lever held down, changing aperture should cause the small lever in the groove to move to an extent dictated by the aperture. Problem is the small lever just moves one click (from 2.8 to 4.0?) and then stops, despite continuing to turn the aperture ring. When the tall lever is to its resting position, using a toothpick i can move the small lever freely along its groove without any changes to the aperture or any resistance. Is any of this normal? I'm pretty sure it's a lens problem and i'll probably have to send it back.</p><div></div>

<p>Ehm... I should really say OVERexposure shouldn't i? I mean the speeds are slower than they should be.</p>

<p>Yeah, looks like the meter coupling lever on your Sigma ain't working. I just checked the only PK mount lens I have and the lever moves the full distance when moving the aperture ring from f2 to f16. Maybe when you get your f1.7 50mm lens you'll be able to check proper function of the meter.</p>

<p>The situation is crazy. If the aperture ring is set to 2.8 when i put the lens on the camera (coupling lever all the way down), then the shutter speed stays the same when i change the aperture and the aperture ring turns throughout its whole range. HOWEVER, if i have the aperture ring a bit stopped down (say 5.6, coupling lever somewhere in the middle) when i put the lens on the camera, then everything works fine, BUT the aperture will not go wider than 4.0 (i cannot turn the ring all the way to 2.8). In other words, max aperture is 4.0, not 2.8.</p>

<p>At mid-aperture, i have turned the lever myself, as it doesn't move there by itself as i already said. </p>

<p>Yep, it's the lens allright. Even in the second case when some response of the shutter speed occurs in response to aperture change, it is way too fast (eg 1/1000 when with a Helios attached via adapter the speed is 1/125 at same aperture and ASA, consistent with my Powershot G11).</p>