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LR import with alpha channel

Apr 18, 2012 11:28 AM

Tags: #export

<Lightroom novice> Can I import a tif image with a alpha channel in it? It seems as though LR will accept the image and allow development but when I export it as tif or psd it goes out as RGB only - the alpha channel is gone. I don't really "need" to do anything with this channel in LR but I can't have it disappear either. Maybe a import/export setting issue - I hope so...

 
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  • Currently Being Moderated
    Apr 18, 2012 11:39 AM   in reply to TLL...

    The alpha channel will be preserved in the original Tiff, but not in the

    exported image. When exporting, Lr bakes a totally new image.

     

    Why do you need the alpha channel in the exported image?

     
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  • Currently Being Moderated
    Apr 18, 2012 12:12 PM   in reply to Dorin Nicolaescu-Musteață

    A TIFF created by exporting a file from LR will also loose layers. Basically, anything that LR doesn't support (i.e. can be edited in LR) will be left out of any file created by an export.

     
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  • Currently Being Moderated
    Apr 18, 2012 2:10 PM   in reply to TLL...

    The first part, LR preserves all data, is because LR is a catalog, it merely keeps track of your images, it doesn't edit them (unless you tell it to write metadata changes to the files). Since LR doesn't support alpha channels, this just means that the fact the image has one will be ignored while working with the file in LR. This also means that when LR goes to create a new file, it continues to ignore the alpha channel.

     
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  • Currently Being Moderated
    Apr 19, 2012 9:58 AM   in reply to TLL...

    LR's non-destructive editing workflow provides a wide-range of tools and output options that work very complimentary with PS, once you understand and accept their differences.

     

    Just as you are interested in "preserving" the Alpha channel for later processing, you also want to save the "original" RGB channels. The same issue exists with film scanner IR image information saved to an Alpha channel for later dust spot removal processing.

     

    Suggestion: Process the "original" TIFF or PSD file non-destructively in LR in the exact same way as "camera raw" image files. All file "edits" are kept in LR's catalog, which should be backed up along with the unmodified "original" files. You can also choose to write all metadata and Develop changes to the "original" TIFF or PSD file, which is useful if you or someone else want to process the files on another system with LR.

     

    At a later date the Alpha Channel information can be applied "non-destructively" in PS using editing layers to "blend" the IR image data. These PS modified files can be re-opened in LR and will now show the applied Alpha channel editing layers. Make any further edits you desire in LR and use the most appropriate LR module to "tailor" the output for your specific usage.

     

    I use this editing method with both PS and LR open, which allows real-time preview of the PS edits in LR. Just save the PS (as you make edits) and you will see the file update with the changes in LR almost immediately. I sometimes do destructive editing in PS (i.e. cropping, content aware fill, etc.) when I am sure this is not removing any image information I might need in the future. You can also add a PS backup layer copy when doing any destructive editing, which also lets you do Before and After comparisons. Disk storage is relatively inexpensive compared to the value of your time & patience.

     
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  • Currently Being Moderated
    Apr 21, 2012 7:31 AM   in reply to TLL...

    TLL... wrote:

     

     

    "All file "edits" are kept in LR's catalog, which should be backed up along with the unmodified "original" files."

    OK, got that too. We probably won't save this once the exported images are approved and backed up.

     

    It sounds like you don't need LR's database tools for organizing, adding metadata, or the various Export modules. You could still use LR to expedite Development editing of the RGB image. One possible solution is to Export the LR edited RGB images full size to a separate folder with the same bit depth and colorspace as the original files. Then use a PS Script to Batch Merge the LR export image to a new layer in the original file, something similar to this one:

     

    http://forums.adobe.com/thread/546727

     

    This way you still have the original RGB image backed up as a layer, which can also be unselected in the merge script.

     

     

    TLL... wrote:

     

    "At a later date the Alpha Channel information can be applied "non-destructively" in PS using editing layers to "blend" the IR image data."

    This is where I'm getting lost. Are you talking about stripping the 'original' alpha channel from the pre-LR image and inserting it into the LR processed RGB image via PS batch/script? That's my thinking as an one approach.

     

    "These PS modified files can be re-opened in LR and will now show the applied Alpha channel editing layers. Make any further edits you desire in LR and use the most appropriate LR module to "tailor" the output for your specific usage."

    No they won't, or do these steps involve only psd files w/alpha channels? The alpha channel (IR data) is still ignored by LR, I have no way to even just keep that information once inside LR nor can I "taylor" a way to save an image with 4 channels of color information inside LR.

     

    I have no idea what you will be doing with the Alpha channel IR image data, but I was suggesting to convert the Alpha channel to a layer mask in PS with 'Blending.' This leaves the Alpha channel as a backup of the IR data. Here's a simulated example using a an IR layer mask I created using LR's B&W IR Develop preset:

     

    IR Screenshot.jpg

    IR Screenshot_LR.jpg

    You can use PS actions with the Batch processor and/or build scripts to do just about anything. In LR you can create Develop presets to apply adjustments across 1,000s of images with a couple of mouse clicks, but no Actions or scripting capability. Like I said, PS & LR are complimentary, but different. I'm not sure which processing methodology is best for your image "end-use" but I hope this gives you some more ideas.

     
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