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12-04-2007, 02:00 AM   #1
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K100D sensor/exposure problem?

Here's what I posted on the other forum, so far no reply there. Maybe some of you can help me troubleshoot what's the problem with my camera:

I just encountered some strange problem with my K100D. 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, trying to check if the image size would be similar to what I get with the macro, the camera just take real dark pictures, i.e. the histogram is narrow band on very left side of the graph, with pretty much no detail at all. This is true when I switch to auto mode and with in-camera flash raised and enabled.

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?

Thanks in advance for any help in solving this mystery.

12-04-2007, 02:16 AM   #2
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I have the K100D and have never found this problem. Check to make sure the batteries are not depleted first. This will happen in any camera constantly using the flash. The voltage drain with SR and flash enabled will override the flash and cause the flash not to fire at full strength, if at all . I use the DA50-200mm for most of my shots because of what I shoot and my wife uses the 18-55 kit for what she does.
Try and give us more information as to what type of lighting you were in and distance from subject and how cold was it where you were shooting. All this may have some effect on what problems your having.
12-04-2007, 03:03 AM   #3
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Here are pics to help troubleshoot:

M Macro Photo on flickr:

IMGP3888 on Flickr - Photo Sharing!

M Macro EXIF on flickr:

Flickr: More detail about IMGP3888

DA Photo on flickr:

IMGP3890 on Flickr - Photo Sharing!

DA EXIF on flickr:
Flickr: More detail about IMGP3890

Thanks very much for your help.

Last edited by LightBug; 12-04-2007 at 03:33 AM.
12-04-2007, 11:13 AM   #4
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The camera miraculously works again. Thanks for all the help.

12-05-2007, 09:10 AM   #5
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QuoteOriginally posted by LightBug Quote
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
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