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"wire removal" on a 16Bit (Half float) EXR file format

Apr 10, 2012 8:38 AM

HI. This query is with regard to a Wire-removal/Touchup process in dealing with16Bit(half float) EXR files. Here is the process we adopted.

 

- Opened a 16Bit (Half float) Exr file in Photoshop, which showed it as 32Bit file

- Since the footage has lot of fire/blast elements among which we need to erase a "WIRE", we need to use "Healing Brush" which doesn't work on 32Bit files. When we tried to 'Convert' 32 Bit file to 16Bit file directly, we get a 'Washed Out' problem, since the shot is over exposed due to Fire/Blast elements in it. So here is a pipeline we used.

 

---- Added "Exposure" (Image > Adjustment > Exposure)

---- Set the "Exposure" to -5 (since it is a over-exposed frame, value -5 depends on exposure values of shots)

---- File > Export > Render Video (OpenExr output)

---- Open the above render file in photoshop

---- Convert to 16bit (Image > mode > 16bit)

---- Use any 16 bit tool for cloning (Eg. Healing tool)

---- Added "Exposure" (Image > Adjustment > Exposure)

---- Set the "Exposure" to +5 (Reversing)

---- Convert to 32bit (Image > Mode > 32Bit)

---- File > Export > Render Video (OpenExr output)

 

After rendering out, we checked the "original footage" with the "output exr" and apart from the Touch-up (wire removal) portion, all other details remain the same. Since this is a high-end hollywood project, can you guys (professionals) confirm whether this process is safe. Please let us know of any optimised workflow.

 

Note1: During the process we found a bug that this process only works, when we render whole footage, meaning if we try single frame, then there seems to be a slight color difference only in the over exposed area. 

 

Note2: When we opened the client input EXR file, under Nuke it shows as "16 Bit (Half float)" but the same when opened under photoshop it shows as 32 Bit file. Why is this?

 
Replies
  • Currently Being Moderated
    Apr 10, 2012 9:35 AM   in reply to prashanthvs

    I think you've posted this in the wrong forum - where were you supposed to post it? As you've noticed there are many different Photoshop forums.

    If you let me know I can move it to the correct forum for you.

     
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  • Currently Being Moderated
    Apr 11, 2012 7:05 AM   in reply to prashanthvs

    My one concern would be with automated healing and content aware filling.

     

    These automated techniques only consider the data in the present frame.  This can lead to apparent quirks when the frames are played back in succession. Nuke offers the ability to address multiple frames. Why not use Nuke if you have it available to you? You can avoid all those conversion steps by simply avoiding Photoshop for this task.

     
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  • Currently Being Moderated
    Apr 11, 2012 9:28 AM   in reply to prashanthvs

    How are you able to obtain the best quality if you are wrecking the color depth and toggling the exposure?

     

    Doesn't the clone tool work at your preferred bitdepth?

     
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  • Currently Being Moderated
    Apr 11, 2012 11:00 AM   in reply to prashanthvs

    First: you seem completely confused between bit depth in files and documents.

    In Photoshop: 8 and 16 bit/channel are integer formats, while 32 bit/channel is a floating point format.

    EXR stores data as 16, 24, or 32 bit/channel floating point - which Photoshop needs to open into it's 32 bit/channel mode.

     

    Converting from 32 bit/channel floating point to 16 bit/channel integer lost any overranged values, and may have applied toning to the image (making the process non-reversible).  Your exposure changes added a lot of quantization, so you probably have 7 bits or less of actual image data left.

     

    >> can you guys (professionals) confirm whether this process is safe.

     

    I can confirm that what you describe is NOT safe.

     

     

    You really need to learn more about the formats and tools before trying something like that.

     
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    Apr 12, 2012 7:29 AM   in reply to Marian Driscoll
     
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  • Currently Being Moderated
    Apr 13, 2012 11:29 AM   in reply to prashanthvs

    No, I'm telling you that it is NOT the same.

     

    EXR is usually floating point.

    Photoshop has one floating point mode (32 bit/channel) and 2 integer modes (8 and 16 bit/channel).

     

    You *are* losing image data/quality when converting and using extreme exposure settings.

     

    The healing brush doesn't work in 32 bit/channel - that's it.  There is no workaround using that particular tool. You can use the clone stamp or other tools that do work in 32 bit.

     

    16 bit float reads into Photoshop's 32 bit float because that's the only thing it can do and preserve data.  Photoshop doesn't have a 16 bit float mode.

     

     

    You really need to learn more about file formats, encodings, and applications before taking on something like this.

     
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  • Currently Being Moderated
    Apr 21, 2012 11:02 AM   in reply to prashanthvs

    Posting the EXR file won't help.

     

    You need to understand the operations that you are using (scaling, toning, etc.) and how they damage the values in your image.

     

    You have a floating point image: if you want to retain the full quality in that image, do NOT convert it to 8 or 16 bit/channel.

     
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