Advanced de-fishing in Lightroom

Discussion in 'Image Processing' started by Bruce McL, Feb 20, 2016.

  1. Bruce McL

    Bruce McL Mu-43 Veteran

    Using a lens profile to de-fish an image in Lightroom works well, but throws away a lot of the image. There is a way to recover some of the image that was thrown away. It involves the “Scale” adjustment located in Develop mode: Lens Corrections: Manual.

    Start with an unprocessed JPEG or RAW image open in Lightroom.

    Use whatever Lens Profile setting you prefer to de-fish this image.

    Hit R to go into crop and straighten mode.

    Stay in crop and straighten mode, scroll down to Lens Corrections, click on Manual

    Highlight 100 in the Scale tool. Use your arrow keys to lower the scale number. Note the white semi-circular areas at the top and bottom of the image. That’s OK. Keep lowering the scale until you see the white areas on the sides of the image. Back off until there is no white on the sides, only on the top and bottom.

    In crop and straighten, change the top and bottom boundaries of the cropped image to crop out the white areas. Hit R again to get out of crop and straighten mode.

    too much:
    too much.JPG

    just right:
    just right.JPG

    Your image is now roughly the same in height as it was before, but is significantly wider.

    The scaling can be put into a develop preset, but not the cropping. However there is a way to batch crop images using the Quick Develop menu in Library mode.

    Screen Shot batch crop.JPG

    If you don’t need all of the extra width, you can select an aspect ratio in crop and straighten, for example 2x3, and lower the scale until the white areas almost touch the sides of the 2x3 crop. This will give you some extra width and a familiar aspect ratio.

    I have added two new develop presets to my tools for the 9mm BCL lens. They are marked 2x3 and 10x16. They automatically select the appropriate lens profile, profile correction value, and scaling amount. All I have to do is crop or batch crop to finish the process.

    Note that I do not use the checkboxes for “Constrain to Warp” or “Constrain Crop.” I find that in Lightroom 5 they cause trouble when I start making manual adjustments for Rotate, Vertical, or Horizontal.

    There is a lot I don’t know about this technique:

    What about clarity, sharpening, and noise reduction? How does scaling affect these tools? I have no idea.

    Will the scaling look awful on paper or cause print heads to melt? I don’t know, I haven’t tried any printing.
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