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12-04-2015, 12:38 PM   #1
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Red Dot in Photos

Hello,

I am new to this forum, and to the Pentax world. I bought my brand new K-3 II about a week ago.

Now the problem is that today I noticed that there is what seems to be a 'hot pixel' on all my photos (I took 5-6 of them), at the same spot. These pictures (attached) were taken at ISO 800, Aperture 5.6 and Exposure 1/30. They are zoomed in at around 200%, but the 'red dot' is even visible at actual size (at least in the darker images). Never before today did I ever notice one. I even looked back into some of my pictures and could not locate any. So my guess is that 'something just went wrong'. What did I do?

Any help would be greatly appreciated!

Cheers,
Ashish

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12-04-2015, 01:02 PM   #2
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Hot pixel?
12-04-2015, 01:07 PM   #3
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Yup, that's a hot pixel. Nothing to really worry about; the camera's pixel mapping feature should be able to get rid of it.

Adam
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12-04-2015, 02:06 PM   #4
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As Adam wrote above, find pixel mapping in the menu and that will fix it for future photos. The sensor has millions of pixels and sometimes one will get stuck on. As a sensor ages it can develop additional hot pixels; just repeat pixel mapping if that happens again.

QuoteOriginally posted by ashykoenig Quote
I am new to this forum, and to the Pentax world. I bought my brand new K-3 II about a week ago.
Welcome.


Last edited by DeadJohn; 12-04-2015 at 02:06 PM. Reason: typo
12-04-2015, 03:22 PM   #5
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QuoteOriginally posted by ashykoenig Quote
'red dot' is even visible at actual size (at least in the darker images). Never before today did I ever notice one. I even looked back into some of my pictures and could not locate any. So my guess is that 'something just went wrong'.
That means there's a prankster standing behind you with a laser pointer. Hold up a mirror and they'll blind themselves.
12-04-2015, 05:41 PM   #6
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As it is always there, and also shows on black background, it's a hot pixel.

If it would show only on brighter background, and additonally was not removed by pixel mapping, it could also be a tiny spot on the filter.
If this would affect only one physical pixel, it would change the colour mix of the the four neighbouring virtual (= interpolated) pixels. In this case the colour of the faulty spot in your pictures would depend on the neighbouring colours, and not be always the same.
12-04-2015, 06:51 PM   #7
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It is a hot pixel all right. Using the Pixel mapping feature should eliminate it.

QuoteOriginally posted by RKKS08 Quote
it could also be a tiny spot on the filter.
not a chance, you can put a piece of blu tack the size of a pinhead on the front element of a lens and you will only barely be able to see it until f/16. Also if it was a spot on the filter or sensor it would be dark, not bright.

QuoteOriginally posted by bar_foo Quote
That means there's a prankster standing behind you with a laser pointer. Hold up a mirror and they'll blind themselves.
I like the way you think.
12-04-2015, 09:00 PM   #8
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Just run the pixel mapper. Most of the other brands necessitate sending the camera to a repair facility...

12-05-2015, 10:15 AM   #9
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Tried Pixel Mapping and it fixed it.
Just did this long exposure shot with no hot pixel in it. I can stop freaking out now.

Thanks for all of your responses!

---------- Post added 12-05-15 at 10:18 AM ----------

Thanks a lot! Pixel Mapping helped

I grew up with a Ricoh point-and-shoot camera. Now I'm excited to own a Pentax!
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12-05-2015, 10:22 AM - 1 Like   #10
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Since only 2 dozen people have said the same thing... yep that is a hot pixel. You can make use of the pixel mapping feature. You're welcome!
12-05-2015, 12:47 PM   #11
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Glad it all worked out for you and problem is now resolved.
12-05-2015, 01:38 PM   #12
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@Digitalis
QuoteQuote:
Also if it was a spot on the filter or sensor it would be dark, not bright.
That's a simplification which is not helpful.
Of course the physical pixel stays "dark" if it is not met by a light beam (or that cell/amplifier does not work anymore). But the user will never see that directly. Even in the raw file the values of each pixel are added ones of what the four physical pixels surrounding it got.

So, what happens with that pixel if the light path to one of the surrounding physical ones is blocked, depends.
If that spot in the picture was dark anyway, nothing changes.
If it would have got some light, the colour balance of the resulting values will change. In most (but not all) cases, this pixel will not show the correct colour, and it will be darker. But there are many combinations possible. For example, if the physical pixel was covered by a blue filter, and the light blocked did not contain much blue, changes will be very small.

What I wanted to say in my last post (and you rejected it) is:
If the light path to one physial pixel is blocked, or the cell is not working anymore ("cold pixel"), you will see in most of you pictures at that position a point with a wrong colour, which also may be slightly darker than it should.
As far as I know, the test facilities of the manufacturers do map these faults, but I have no information whether the built-in pixel mapping of the bodies can do it as well.

I think I stumbled on this when I remembered the discussions in a German forum about the faulty ROM routines of the K20D for making hot/cold pixels unvisible. It probably was cured with an update, I never owned that model. The result was that, if such a pixel was met by a contrasty line of the scenery, coloured points could emerge (even if the scenery shot was just b&w in this area). I think this was dependend on whether the line was horizontal or vertical. Pixel mapping did not help, as in some respects the fault was a result of pixel mapping.

Last edited by RKKS08; 12-05-2015 at 01:48 PM. Reason: Info added
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