Tuesday, March 20, 2007

Run Spot Run

I've been saying for a while now that I need to clean the image sensor on my camera. And here's the shocking proof. The images above and below are shots taken of a plain white background with the aperture stopped way down, making it a long exposure with just a small amount of light entering the camera. It's also deliberately out of focus and handheld, so anything sharp on the final picture is internal to the camera. The black dots you see are pieces of dust, dirt or some unknown sort of crud on the image sensor in the heart of my camera. I suppose this is the price you pay for having a camera with a removable lens. Every time I change lenses, the interior of the camera is exposed to the elements for a few seconds. Over time, a mess builds up. I need to either learn to clean it myself, or get someone to do it. I'm reading up on the process here. FYI-looking at the image sensor doesn't reveal much of anything. I can't spot anything on the surface. I'm probably exposing it to more dust just by opening it and looking. What's the difference between these two shots? The one above is at a lower ISO setting (100). That means I should get a clearer picture with less noise in it. The shot below is at ISO 800, and I think it's a little rougher. Both shots were processed in Photoshop to highlight the defects. I find the dark corners interesting, too. I guess the better your lens, the less of that you get.

So, what effect is this dust having on my final pictures? Plenty. That big chunk at lower right shows up in just about every picture I take of the sky. It's there in all my pictures, but it's often mixed into the image such that it's hard to spot. But it's still making my images less sharp. I really blew the contrast out of the water, but the image below shows the spot. I see it on almost all of my shots, always in the same place. If I want to use the picture, I have to spend a few minutes in Photoshop trying to clone over it. It's a pain.


Anonymous said...

Where is that spot located, exactly? I ask, because I have one, too, and it's in the very same spot in every picture I take. Mine is situated almost in the very right bottom corner.

Ernie said...

The spot is on a glass low-pass filter located just in front of the actual CMOS sensor at the back of the camera. I ordered a kit yesterday that should have all the tools I need to get in there and properly clean the internals. I'll post when I get some results to share.