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craftyste123
Participant
September 4, 2010
Answered

Selecting the difference between two images

  • September 4, 2010
  • 4 replies
  • 45822 views

Hi

I have two photographs exactly the same which I have taken using a tripod, lighting and general studio conditions.  However, in the second picture I have inserted an subject - in this case an intricate sculpture.  Can Photoshop merge those two images together AND in doing so select the difference between the two images - in this case the intricate sculpture?

Basically I need to select the sculpture and don’t want to spend the time manually selecting it due to its complexity.  I need to separate the background and sculpture for editing on their own layers.

Thanks

Stephen – CS3

    Correct answer Reynolds__Mark_

    You posted this in two forums, its been answered in the mac forum.

    4 replies

    N
    nawyer
    Participant
    July 25, 2021

    I actually came here just to double check there wasn't a better way but I see there is some confusion as to whether this is answered so here's mine: invert the top layer and switch the blending mode to linear burn.

    We had a person leave who made a cool gif that I wanted to use for a new campaign but unfortunately I can't get the layered file from him and need to recreate it manually. Its very complex and has 68 frames I need to rebuild where a semi-transparent water splash is the subject to be masked.

     

     

     

    As you can imagine the transparency of the water would be a problem.

     

    So, I make a quick action to 1) go to the next frame and select the target layer 2) invert the layer and change the blending mode to Linear Burn 3) create a mask from the output

     

    and youre done!

    Trevor.Dennis
    Community Expert
    Trevor.DennisCommunity Expert
    Community Expert
    July 25, 2021

    That's a nice animation, but I'd hate to have to reproduce it with Photoshop.  68 frames is precious little to get such beautifully fluid movement.  Do you know what app your ex colleague is likely to have used?

     

    I wonder if After Effects would be be the tool to use?     @davescm could the animation be done with one of the 3D apps?

    davescm
    Community Expert
    davescmCommunity Expert
    Community Expert
    July 25, 2021

    @Trevor.Dennis  Yes a water splash animation can be created in a 3D application with a fluid physics simulation. Doing it that way, the liquid and object in the glass would also move realistically not just the separate splashes above the glass as in the above animation.

     

    Dave

     

    Noel Carboni
    Noel Carboni
    Legend
    September 4, 2010

    I'd probably put one image over the other as a layer, set the mixing mode to Difference, carefully align the two images to minimize the differences, then Select All and Copy Merged.

    After that I'd paste the result as a new layer or channel and enhance it (e.g., with Curves) to black out the similar parts and white out the differences.  You will probably have to paint on this by hand to clean it up a bit, because no two exposures are ever identical.

    Then you can Select All and paste as a new channel, or use the data as a mask, or whatever.

    -Noel

      Reynolds__Mark_
      Reynolds__Mark_
      Inspiring
      September 4, 2010

      That precise method, without all the unecessary merging of layers and faffing around has already been suggested Noel. Twice.

      There is another way, by simply inverting one of the layers. And using Vivid light on it. Using Color Range to isolate the gray you can generate a difference mask in this way too. Many ways

      Noel Carboni
      Noel Carboni
      Legend
      September 4, 2010

      Reynolds (Mark) wrote:


      That precise method, without all the unecessary merging of layers and faffing around has already been suggested Noel. Twice.


      So?  Does it hurt to have more than one description?

      Regarding "faffing around", do you have a definition for this nonsense?  PC users tend to be more down to Earth and prefer real English words. 

      -Noel

        JJMack
        Community Expert
        JJMackCommunity Expert
        Community Expert
        September 4, 2010

        Photoshop Extended has stack mode blending options that most likely could do what you want in standard Photoshop this is grayed out its under menu Layers>Smart Objects>Stack Mode..

        Even though the images were taken on a tripod there is most likely dome difference other then the inserted object between the two images due to exposure, background objects moving and camera movement.  Try selecting both layers and use auto align layers then set the top layers blending mode to difference. Stamp visible layers into a new layer you may get a good outline of the statue. and be able to create a mask from this new layer.

        JJMack
        Reynolds__Mark_
        Reynolds__Mark_Correct answer
        Inspiring
        September 4, 2010

        You posted this in two forums, its been answered in the mac forum.

        acewofl
        acewofl
        Participant
        April 25, 2021

        This isn't helpful to the rest of us as a selected answer.  Could you please link to the other post?

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