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I've placed a camera on a tripod and took photos of different objects, one object per photo, in different positions.

  • Some objects are out of focus due to little depth-of-field.
  • Some objects overlap if cut-pasted to a single image.

How can I combine all the photos to make it seem like all objects were there at the same moment? Using a green (or any other color) cloth behind the objects is an option, but I don't know how to later remove this cloth and transform it into alpha.

  • Definitely "focus stacking" is what you need. A very creative approach taken from the microscopic domain. – sepdek Dec 30 '14 at 9:41
  • Focus stacking isn't appropriate, as I want to preserve the out-of-focus blur. – Michael Litvin Dec 30 '14 at 10:04
  • it is possible that I got it wrong. Do you mean you have a scene constant in all photos and you add and remove objects? If this is the case then you seem to need to put all these layers on top of each other and mask out everything except the object. – sepdek Dec 30 '14 at 10:10
  • Yes, this is the case. But how do I mask the blurred edges? In these areas several objects need to be blended. – Michael Litvin Dec 30 '14 at 14:01
  • If you have to do it "scientifically" it is a bit complex: you have to apply an algorithm that will detect the background that is common in all cases and remove it in all object photos. This is typical in camera-based security applications. – sepdek Jan 1 '15 at 8:40
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The technique you're talking about is called compositing. It can be both time consuming and technically challenging and require a software program like Adobe Photoshop or something equivalent.

there are a couple of alternatives that might make sense.

One is to retake the shot with a much deeper depth of field. It might be a lot faster and give you better quality to do this than to try to patch the images together by hind.

It might be possible to merge the images together using a tool that does focus stacking processing, which finds the sharp parts of each image and stacks them together to combine all of the sharp parts. Depending on how you took the images this might or might not work because it requires a stable camera and a series of shots that move the sharp part of the depth of field across the subject (see http://en.wikipedia.org/wiki/Focus_stacking for more)

Chances are, if you aren't a bit of a photoshop whiz, an attempt to composite something like this will end up disappointing with the result. It's rarely easy (or possible) to take flawed photographs and patch them together in a way that doesn't look patched together.

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