Originally posted by LightBug I was shooting away with it using my Pentax-M 100mm F4 lens with in-camera flash enabled. Then I switched to my DA50-200mm lens. I got few shots at 200mm, then when I changed the zoom to 100mm, ... the camera just take real dark pictures. ... I then switched to my 18-55 kit lens, same thing when flash is used. I switch back to my 100mm manual macro lens, K100D works fine with the macro lens. But I can't seem to take any photo with my auto-focusing kit lenses anymore, what gives?
This seems a bit strange. A couple of things came to mind, but we need more information. First, with the kit lens is the view finder bright? That is, is the kit lens kept at full aperture when it is on the body? With the kit lens (and an M lens) the aperture will be wide open until you take the photo, or use the DOF switch (or with the M lens, use the AE-L button in M mode). If the viewfinder is bright (assuming you have optical DOF preview Custom setting), just for your peace of mind, set the camera to Av, set to a small aperture (say f11) and make sure that when you use the DOF switch the viewfinder goes darker. If so, then the coupling between the body and the aperture actuator on the lens works.
If that is the case then you need to work out if the camera is using a correct exposure. Did you use M mode? If the camera is in M then you won't actually use the metering unless you tell the camera to use it (press the AE-L button), so you might just be using a small aperture and fast shutter speed that's not appropriate to what you are shooting with the kit lens.
To test that the metering is working in M point the camera to an outside scene on a sunny day, press AE-L and see if the value follows the sunny 16 rule (that is on a sunny day at f16 the shutter speed is 1/ISO). So assuming ISO 200 the meter should read f16 and 1/200th. (Adjust accordingly, so if the meter gives f8 the shutter should be 1/100 and so on). In Av mode it's easier - just set to f16, point the camera to the sunny scene and the viewfinder should show 1/(ISO setting) for the shutter.
Richard