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The camera on my HTC One phone adds a strange purple cloud pattern to one end of an image when the light is low.

What is a good technique I could use to remove these, or is there one, using Photoshop 6.0.1?

I have tried working with the various options under Image-Adjust, and the closest thing to working well seems to be Replace Color with fuzziness 40 or less and a low Saturation adjustment, though I have to use the dropper+ or else I don't get it all (just reducing and changing the magenta clouds) or it ends up changing some of the magenta to black.

It seems like there could be a way to filter out this cleanly since it seems to be added magenta to images with no magenta in them. Does anyone know a better way to do this?

Here is the noise taking a picture into darkness. Here is an extreme example of it affecting a dark picture. Often it is less than this, or not noticeable at all if there is enough light.

Often it is less than this, or not noticeable at all if there is enough light.

  • Interesting that magenta is red+blue, and the sensors and bayer processing treats green and r+b differently. It might really be a problem with green being too low, or subject to excessive noise. Use rawdigger to look at the unprocessed sensor data and see what's really happening. Oh, it's a phone? I don't know if there are utilities to get raw data. You can also try a different camera "app" on case it's a processing bug. – JDługosz Jun 4 '15 at 0:57
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    You could post on woowoo sites and claim you're detecting auras or ghosts or something. Then sell the phone on eBay for an inflated price to the incredulous. Being intermittent is all the more convincingly mysterious. – JDługosz Jun 4 '15 at 0:59
  • @JDługosz Good ideas! I tried another camera app and it's the same behavior. When I first saw the purple cloud, I was taking a picture of a dark cat and I thought I was picking up cat dream magic or something. But it's always a constant unmoving pattern. – Dronz Jun 4 '15 at 6:06
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is this what you wanted?

done with gimp (loaded both images as layers, adjusted the size/position to match, dimmed the dark part of the pattern using "curves" and then subtracted the pattern layer from the photo)

subtracted the first magenta pattern from your second photo

  • Yes, thanks, that's pretty much it. Though since it comes in different intensities, which creep in I think at a different rate than the high-end reference noise, I probably would need a range of examples to use. Probably more work than it's worth, but yes, that looks pretty close, and would be useful for images that are worth the effort! :-) – Dronz Jun 5 '15 at 19:55
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This don't answer your question regarding the use of Photoshop 6. But resolves your problem.

Use a noise remover like this one: http://www.neatimage.com/ You can make a noise pattern profile of your camera and use it to remove noise taken is the same iso settings.

There is a chance it can work as a plugin for photoshop. But you can use it as a standalone aplication.

If the magenta cast is not noise but a general tone can be related to some adjustments in the camera. In some cameras, you can adjust the color temperature (red-blue) and the tone (green-magenta)

  • Is it possible to use Neat Image to filter out the irregular pattern as above? I am trying using it for the first time, and to make a noise pattern profile it has me select a small box, but the box is much smaller than the pattern, which is about the size of the whole image and doesn't repeat predictably. – Dronz Jun 3 '15 at 20:01
  • Oh. My God! What is that! I answered the question before you posted thoose images... NO that is not noise... That is a blob invasion. :o) No It can not remove it. – Rafael Jun 3 '15 at 20:07
  • Oh ok. Yeah it is strange, eh? It only emerges when the lighting is low, and is sometimes quite faint, sometimes not there. – Dronz Jun 3 '15 at 20:24
  • Probably your sensor is "burned" or something like it. – Rafael Jun 3 '15 at 20:29
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Something tells me that your phone's camera has a defect of some kind. Warranty issue perhaps. I would look into it if you want to verify what is going on.

  • Yes, there is some sort of defect with it. Out of warranty though so now it's just a special "feature" ;-) – Dronz Jan 24 at 0:00

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