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Blue dot in the picture with sx20is

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Blue dot in the picture with sx20is
« on: 07 / June / 2010, 12:06:00 »
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While on a recent vacation, I noticed that I was sometimes getting a blue dot in the picture if it was shot with a blue background. I've uploaded a few examples to flickr for you to check out. IMG_1062
I have a lot of blue sky shots that don't have the dot, and maybe 7-9 shots that have it. I also noticed that almost all the shots with the blue dot happened the first day we were there, one picture from the second day has it, and it's no where to be seen on days 3-5. I'm not sure if this was something that worked itself out, or if I should worry about this happening again. I haven't had a chance to use my camera much since we got back, so I'm not sure if it is still doing this. I hope not.
Any ideas?

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Offline hotvedt

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Re: Blue dot in the picture with sx20is
« Reply #1 on: 07 / June / 2010, 14:17:15 »
Looks like dust on the sensor. It will be more visible (but smaller) with a smaller aperture. The dot is probably not blue, but dark.
Try taking some photos of for example a white sealing, out of focus, with your smallest aperture (highest F-number),
and look at the result. Auto-levels in photoshop may make it more visible.
« Last Edit: 07 / June / 2010, 14:18:59 by hotvedt »

Re: Blue dot in the picture with sx20is
« Reply #2 on: 07 / June / 2010, 15:29:36 »
Well, looks like dust is the case. Aimed it at a white background with the smallest aperture, and the dot appeared. What would be the best way to clean the sensor when the lens doesn't come off?

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Offline hotvedt

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Re: Blue dot in the picture with sx20is
« Reply #3 on: 07 / June / 2010, 16:24:38 »
Use warranty if possible. I suspect it is very hard to clean it yourself, and get a result that is less worse than it already is.

I have a dslr with some dust that appears with smaller apertures. There i try to avoid it by using bigger aperture when possible,
or clone it out in photoshop.


Re: Blue dot in the picture with sx20is
« Reply #4 on: 09 / June / 2010, 17:59:09 »
Damn, that's a pain in the [admin: avoid swearing please].

Thanks a lot for your help.

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Offline wontolla

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Re: Blue dot in the picture with sx20is
« Reply #5 on: 09 / June / 2010, 19:20:49 »
I had the same issue once. I used a can of compressed air and blowed a little near the edge of the lens. After a few attempts the dust disappeared. It probably is still inside the camera, but at least not on the lens.

 

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