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I took a photo on my phone where everything appears twice. When zoomed out, it just looks blurry, but when zoomed in, you can see a faint, slightly shifted copy of the original subject.

See below a sample from the photo. It's a drawing of a circle with three arrows, but there is a fairly crisp shifted ghost image overlapping.

Ghost image

What's the best way to correct this?

Edit:

The HDR option on my phone was turned off.

Flash was not used.

  • Do you have any image editors available to you? – Crazy Dino Apr 12 '17 at 10:30
  • @CrazyDino I have GIMP. – nnn Apr 12 '17 at 11:29
  • @nnn was there a flash involved? – Michael C Apr 12 '17 at 17:24
  • @MichaelClark nope – nnn Apr 13 '17 at 13:50
  • By "everything appears twice", are you referring to a multi-exposure? – WClarke Apr 15 '17 at 0:59
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the drawing is smeared between the main image and the ghost, which makes it look like a motion blur. such movements can be quite random and you get more focused "ghosts" in the motion path wherever the motion pauses for a moment.

it should be possible to improve such images by applying the motion blur correction if the given algorithm is smart enough to deduce the atypical shape of the point spread function.

we have some software recommendations in the motion blur question: Can anyone recommend *freeware* to reduce motion blur by deconvolution?

  • Thanks for the link. I don't have Windows/Mac, and don't have time to figure out the ImageJ plugin, so I will likely give up for now. – nnn Apr 13 '17 at 13:49
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It's possible to painstakingly correct by hand, and there might even be something you could do in math-focused image manipulation software to cancel out the doubling, but — especially when it's something like this! — the best thing to do is simply to re-shoot.

  • Yes, there are standard algorithms to fix this -- basically they do a correlation integral over one or both axes and add/subtract a fraction of each pixel's value based on the correlated pixel. Whether these are available in common commercial photo-manipulation apps I don't know. – Carl Witthoft Apr 12 '17 at 11:47
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The problem is that you moved the camera as the picture was being taken. It looks like this was indoors, so the shutter speed was probably slow. Most likely, the motion is due to your pressing the "button" to take the picture. Real cameras are designed for the shutter trigger action required by your finger and hand to cause minimal camera motion.

The way to fix this is to be more careful in the future. There are fancy algorithms that make assumptions about the camera motion and try to correct for it. Sometimes they work somewhat.

As a aside, no, this is not due to auto-HDR where the camera takes two pictures. If it were, you'd see two distinct images. What you actually see are two images with smudging between them. This is particularly evident at the bottom arrow. The camera was more still at the beginning and end of the exposure, and moved rapidly some time in the middle.

  • Either that or a weak flash fired at the beginning of the exposure while the camera was moving and then the camera settled into the same position for the end of the exposure. – Michael C Apr 12 '17 at 17:24
  • You're probably right; I didn't look closely enough. – mattdm Apr 13 '17 at 15:09

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