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PRINT Virtual copy; jpeg file losses

Discussion in 'Output Modules' started by David PZ Wong, Dec 21, 2016.

  1. David PZ Wong

    David PZ Wong New Member

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    (1) Please let me know if my understanding is correct or not. When I import image files, they go on the hard drive and copied into LR. Am I right in saying that what I have now created in LR are basically virtual copies? We don't call them virtual copies because they happen to the first copies in LR?

    (2) Everything done in LR is nondestructive (although I read online that many say rotating the image is destructive; I believe it's false and hope I am right.)

    I shoot jpeg with my iphone. I understand that when I export a file to say desktop, there will be some losses. If I do not use any virtual copy, but exporting the master copy in LR, would that master copy be affected back in LR? My educated guess is that whether you use the original or a virtual copy of it for export, you can do it a thousand times and there will be no losses happening to the master copy back in LR. Please assure me that I am right or correct me if I am wrong. [If I am right, then it seems justified to say that the first copy in LR is a virtual copy, which I asked about in (1)].
     
  2. JohanElzenga

    JohanElzenga Lightroom Guru Staff Member Lightroom Guru

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    It's better to compare Lightroom with an address book. Your friends are in your address book, but that doesn't mean they are physically in there. Their data are in the database. Everything is data, so non-destructive. Including rotation.
     
    Last edited: Dec 21, 2016
  3. JohanElzenga

    JohanElzenga Lightroom Guru Staff Member Lightroom Guru

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    And exporting creates a new file, so it doesn't do anything to the original.
     
  4. clee01l

    clee01l Lightroom Guru Staff Member Lightroom Guru

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    Saving a copy of the original JPEG is not going result in an image that has more data loss than the original JPEG.
    In the sense that the JPEG algorithm throws away some data when the file is first created there will always be some loss from the data recorded by the photosensor. Once the file is created no further data is lost from that 1st generation JPEG. If you open that 1st generation JPEG in an image editor, the file that is created from that editor is a 2nd generation JPEG and additional data is thrown away to create the 2nd generation JPEG. The 1st & 2nd generation JPEGs don't show a significant loss to the naked eye. However, if all you have to work with is a 4th or 5th generation JPEG, the data loss can be seen. It is for this reason that you want to save your original image in a lossless RAW format. That way the first image out of the Editor is always going to be a 1st generation JPEG

    Newer iPhones can capture images in RAW format.
     
  5. David PZ Wong

    David PZ Wong New Member

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    Thank you, Johan and Cletus. Cletus' response is a little to advanced for my understanding. Talking about opening the JPEG in an image editor, is LR an image editor? If not, can you give an example of opening the file in an image editor? Would always working with virtual copies, thus leaving the original alone, the way to go? Sorry that I do not have an overall clear picture.
     
  6. clee01l

    clee01l Lightroom Guru Staff Member Lightroom Guru

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    Lightroom Uses parameterized editing (PIE — Parameterized Image Editor). That is the app does not change the pixels in the file but merely records parameters to change those pixels on the display and in the computer memory. This is why there is no Save option in LR. Photoshop OTOH is a pixel editor. In it, adjustments are made to the file in memory and when the save option is used those changes go back and overwrite the original file.
    JPEG is considered a lossy file format in that the file is compressed before it is saved. When another app opens the file it is uncompressed and not all of the pixel data that was present before the file is saved is recovered. So then if you save that file opened in the other app, it will be compressed again and more data is lost. If the app that opens the compressed JPEG saves the file in the same file that was opened, then more data is lost.
    LR won't let you save the changes back to the original file for this reason. When you use LRs Export function, you create a derivative file with a new name in a new Location. The derivative file merges the instructions to change the original with the original file's data, making a new changed file.

    In LR you can have multiple sets of instructions The first set of develop instructions is called the master copy. If you want a different set of instructions for the same original file, you create a second copy of the instructions called a Virtual Copy to distinguish it from the Master copy. If your master copy develops the image in color and you want to produce a B&W version of the same original then to create a virtual copy and render the changes in B&W and then you can export both the master copy (color) and the virtual copy(B&W) and have two derivative images based on the same original image.
     
  7. David PZ Wong

    David PZ Wong New Member

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    Cletus, I appreciate the detailed response. To be frank, your knowledge is so much above my elemental understanding that I still have my basic questions. I'll simply ask them here for you to respond yes or no and I'll be satisfied.

    (1) I know that if I export (save) the master copy in LR to the desktop, that jpeg copy on the desktop now outside of LR would have some data loss. Is the master copy back in LR still intact? (Based upon Johan's answer above, the answer should be yes, which I tend to agree with.)

    (2) if the answer is no, then would exporting a virtual copy of the master copy avoid this problem?

    Thanks in advance.
     
  8. JohanElzenga

    JohanElzenga Lightroom Guru Staff Member Lightroom Guru

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    Yes, nothing happens to the master copy.

    As Cletus explained, a virtual copy is nothing more than an extra set of instructions. Exporting from a virtual copy isn't any different from exporting from a master copy. In both cases you create a new file, the master image remains untouched.
     
  9. I-See-Light

    I-See-Light Active Member

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    David, I am reading this thread and must correct two of your statements-
    1.
    Wrong- they are not copied into Lr. Only previews are created in Lr. The single and only one original file exists on the hard-drive in the destination you imported it to.

    2.
    No. Again a mis-understanding- No images or files are 'IN' Lightroom,only previews in the database.

    Your Master original files in a folder of your hard-drive must be preserved at all costs, and back-ups made of these files, independently of Lightroom.
     
  10. David PZ Wong

    David PZ Wong New Member

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    Thank you Johan & I-See-Light. The people on these forums are truly a great bunch!

    May you all have a great New Year, photographically or otherwise.
     

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