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03-31-2015, 09:14 PM   #1
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What is this?

Can someone please tell me what the heck this blue dot is to the left of the knife block?


Last edited by jayman_1975; 04-05-2016 at 06:49 PM.
03-31-2015, 09:16 PM   #2
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dust? kinda odd to be a bad pixel....maybe pixel map?
03-31-2015, 09:19 PM   #3
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Stuck pixel, maybe? As described here:
https://photographylife.com/dead-vs-stuck-vs-hot-pixels
03-31-2015, 09:21 PM   #4
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It shows up at different spots on the wall depending on how far im zoomed in. Would a bad pixel act that way?

03-31-2015, 09:25 PM   #5
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Does it appear with a different lens on the camera? Do you see any blemish on the lens in question? On the mirror?
03-31-2015, 09:34 PM   #6
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happens with two different lenses. ill have a look at the mirror.
03-31-2015, 09:37 PM   #7
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doesn't the mirror flip up when the shot is taken? wouldn't it only be seen in the viewfinder if it were?
03-31-2015, 09:49 PM   #8
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To me it really looks like failed pixel mapping, since it's perfectly circular and has a little halo. Does it show up in unprocessed raw files?


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03-31-2015, 10:47 PM   #9
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You do not mention what body is producing this, but anyway, it surely looks like a bad (hot) pixel. The halo effect is normally produced by the camera's alogarithms that handle jpeg compression as well as sharpening and contrast alogarithms. This phenomena is most evident on jpeg images (from camera) and if the bad pixel falls within a relatively smooth or even image (the wall in your case).

If shooting raw, the bad pixel will be just white but with no halo or compression artifacts. If your camera has pixel mapping, then a single pixel map course should fix this.

I've seen this happen with my *istD. For piece of mind, no sensor is 100% free of defective pixels. Every sensor (new) will show a fair amount of bad pixels, around 0.03% of them (on a 20 Mpix sensor, the average bad pixel count that should be "mapped out" at quality control, is around 4000!)

After mapping out bad pixels (factory quality control), around 3% on the sensors will produce new bad pixels, but in very small quantities (2-3 bad pixels per year). The pixel mapping in camera is used to deal with this small amount of bad pixels.

Last edited by rburgoss; 03-31-2015 at 10:53 PM.
04-01-2015, 05:37 AM   #10
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Yup. Turned out to be a bad bad/stuck pixel. Did pixel mapping and its gone. It's a k5IIs.
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