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06-06-2010, 12:56 AM   #1
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Can sensors go bad?

Hi, I'm new here. I'm primarily an artist but nowadays I do photography more than paint. I've been a serious photographer for over 25 years. I've got a dark room, (which I don't use anymore) and this DSLR is my 4th Pentax camera. I've had a Pentax *ist D since about the time they came out. (I think someone's cat got on the keyboard and gave it that strange name.) To be perfectly honest, I haven't been happy with the camera. The auto focus stinks and I miss a lot of shots. But it has always taken good pictures when I can get it to fire.

For the last couple months, the pictures are all over exposed and the high lights especially are washed out. It doesn't matter what lighting or which lens I have on the camera. It's hard to even correct them on my computer. Today it was overcast and the lighting was very soft and it still did it. None of the setting had been changed. I've tried changing the lighting and contrast setting and changing which meter pattern I use. I can only make it worse. Could my sensor be going bad?

Thanks

06-06-2010, 01:57 AM   #2
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Give us some full sized samples with EXIF intact.

To answer your question - yes they can. Often in two cases - when they are brand new (defective sensor) and when they are VERY old (had a LOT of use).

But if the sensor didnt show any odd behaviour before, or dosn't gets worse, it might as well be somethig else. Dying sensors usually get smeared stripes which progress untill the whole frame is white or black. Sometimes it is just a bad contact (sensor detached from board).

Last edited by ytterbium; 06-06-2010 at 04:43 AM.
06-06-2010, 02:36 AM   #3
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QuoteQuote:
None of the setting had been changed.
Without being nasty, did you check that?

Although sensors can go bad, overexposure/underexposure is often user error; in this case possibly unknowingly. I suggest that you first set everything back to factory defaults and work your way through the settings or thoroughly check all your settings.
06-06-2010, 11:25 AM   #4
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Aside from user error (eg, dialing in compensation or switching to spot metering without realizing it), if it does turn out to be an equipment malfunction, it's more likely to turn out to be the aperture blades on the lens getting partially stuck than a sensor issue.

06-06-2010, 12:19 PM   #5
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What lenses are you using ?
06-06-2010, 12:43 PM   #6
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"Give us some full sized samples with EXIF intact." I'm new here and don't know how to do that. I'll see if I can figure it out. Thanks
06-06-2010, 12:53 PM   #7
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QuoteOriginally posted by sterretje Quote
Without being nasty, did you check that?

Although sensors can go bad, overexposure/underexposure is often user error; in this case possibly unknowingly. I suggest that you first set everything back to factory defaults and work your way through the settings or thoroughly check all your settings.
That is the first thing I checked. The camera has always took good pictures at the factory default. I went through and checked everything and they were still at factory default. Then I went through the settings one at a time and tried to fix it. I tried switching from multi pattern metering to center weighted. I even took a few test shots with the spot meter. I expect pictures to be contrasty in harsh mid day sun but these are like that even in soft light. To an ordinary snap shooter, they would be "ok" but this camera has always done better that that.
06-06-2010, 12:58 PM   #8
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QuoteOriginally posted by Marc Sabatella Quote
Aside from user error (eg, dialing in compensation or switching to spot metering without realizing it), if it does turn out to be an equipment malfunction, it's more likely to turn out to be the aperture blades on the lens getting partially stuck than a sensor issue.
I've had aperture blades stick before. I've been doing this long enough to wear out several lenses. That is exactly what it acts like but it is doing it with both of the main lenses I use. I have a Pentax 12-24 lens I just bought and haven't used very much yet. I'll try a few test shots with it.

Thanks

06-06-2010, 01:06 PM   #9
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QuoteOriginally posted by LucVer Quote
What lenses are you using ?
A Pentax 18-55 zoom and a Tamron 28-300 zoom. It does it with both. I just bought a Pentax 12-24 zoom but I haven't used it much yet. I'm going to do some testing with it. The previous person suggested that maybe my aperture blades are sticking. It's unlikely that it is doing it with both lenses but I suppose it is possible. That is exactly what it acts like. Or maybe it is something mechanical in the part of the camera that controls the aperture. I'm going to do some testing with the camera in manual and at different apertures.

Thanks
06-06-2010, 04:28 PM   #10
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QuoteOriginally posted by J Merrill Quote
A Pentax 18-55 zoom and a Tamron 28-300 zoom. It does it with both. I just bought a Pentax 12-24 zoom but I haven't used it much yet. I'm going to do some testing with it. The previous person suggested that maybe my aperture blades are sticking. It's unlikely that it is doing it with both lenses but I suppose it is possible. That is exactly what it acts like. Or maybe it is something mechanical in the part of the camera that controls the aperture. I'm going to do some testing with the camera in manual and at different apertures.

Thanks
Red = Unlikely

Blue = More likely

Sounds like the lenses are being held wide open during exposure regardless of setting. If you happen to have a manual lens, one with an aperture ring, try that.

06-06-2010, 05:34 PM   #11
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QuoteOriginally posted by J Merrill Quote
"Give us some full sized samples with EXIF intact." I'm new here and don't know how to do that. I'll see if I can figure it out. Thanks
Easiest way is to open a free account with photobucket or picasaweb, ulpoad you picture, then paste the URL of the uploaded image here. Or you can use the "attachment" feature of this forum (see the buttons below where you type your post). You can also post to flickr, but it strips exif when it resizes, so you'd have to resize before posting, to a size smaller than flickr's largest non-pro size. Although it looks like someone suggested a full size sample, don't do that - the images would be far too big to see all at once, and we don't need to see the image that big to tell if it's overexposed or not. The sites I mention all resize to a usable size automatically on upload.
06-06-2010, 10:09 PM   #12
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Does your camera have optical DOF preview (I don't have the manual at hand)? If so, you can test if the aperture closes.
Set aperture to e.g. f/16 and activate optical DOF preview. You should see the image in the viewfinder go dark.
06-06-2010, 10:24 PM   #13
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I use *istD also and it does have tendency to blow out highlights. However, it was never a problem for me. I think a sample pic with full EXIF will let us help you better.
06-06-2010, 10:48 PM   #14
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Some test results

I had sort of a busy day but I went out this evening and did some testing. See if you can open this; Picasa Web Albums - jlmerrill73
A shot aperture priority through all of the f-stops on my three main lenses. I didn't upload all of them.

The first one is my 12-24 zoom stopped way down, the second one is with it wide open.

The third is my 18-55 zoom stopped down and the forth is it wide open.

The fifth is my 28-300 stopped down and the last is it wide open. This lens showed the most difference but not a lot.

As you can see they are not real bad, but these were taken in the shade as the sun was going down. The highlights are blown out like it was mid day. It just started doing that about a month ago. It is really bad in bright sun, even with a polarizing filter.

I have a manual 50mm lens off of my 35mm camera and I will do some tests with it tomorrow. I ran out of sun today and if I did this with a flash, it would just complicate things.

Thanks for your help and suggestions.

Last edited by J Merrill; 06-06-2010 at 10:56 PM.
06-07-2010, 07:50 AM   #15
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Hard to say without the EXIF info. Could you repost without stripping that off? Presumably the program you used to resize did this? Like maybe you used Photoshop's "save for web" option? Don't do that; use the resize fucntion, or better yet, as I said, don't resize at all and let picasaweb do it for you.
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