Thursday, December 07, 2006

A dirty little secret

click on this photo to see the shadowy dust spot in more detail
My new Pentax K100D isn’t even a week old, and horror, there is a black dot in the middle of the picture, there it is again in exactly the same place on the next frame, there again, and again…. My first thought was a dead pixel, nothing in the troubleshooting about that, in fact dots on pictures aren’t mentioned anywhere in the troubleshooting section or the index…. What it did find, after a lot of looking, was instructions to clean the CCD, and yes that was the problem. Something like dust on my CCD, that goes all the way back to my first photos I just didn’t notice them at the time. Yes tem, there were at least three. So the dust was in the camera when I purchased it (or as I screwed on the first lens)

Cleaning the Pentax wasn’t hard but it must be done with care, follow the instruction in the manual exactly. There is a menu item to lift the mirror and you can use a blower (not a brush blower) to gently blast air over the CCD. There are numerous warnings, to many to cover here. SO READ THE MANUAL! However I had to do it four times, which brings me to the real purpose of this blog post.

How do you know that your CCD requires cleaning?

It is easy to test for a dirty CCD. Aim you camera at the sky on a nice clear day, away from the sun, so the sky is evenly exposed. Take a few exposures moving the cameras around. A few clouds, a bit of a tree or horizon can help you make sure you do this. Then upload the photo to your computer and have a look at a large magnification, in software that lets to scroll from one image to the next. If to see a shadowy spot and it is the same position within the photo frame its very likely to be dust on the CCD
A well lit sky makes it easy to see the dust shadows Moving the camera around confirms the dots are in the same position in the frame clean at last!

WARNING: looking around on the net with the key words like digital, slr, cleaning, ccd, cmos it would appear that the web is awash with complaints and horror stories. Also some of the articles may not be all that well informed. If you can not find instructions in your camera manual be careful about trying to clean its CCD. In fact don’t, take it back to the dealer, or a reputable camera shop. Nikon digital SLR owners must pay particular attention to Nikon’s disclaimers about this. If you own a Nikon I suggest you read the article by thom about cleaning your camera.
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