Lightroom Local

[rwest01]

Lightroom Version Number

7.1.2

Operating System

1. macOS 10.15 Catalina

I've been playing around with Lightroom for the first time, considering moving from Classic. But here's a mystery: I understand that editing a raw file creates a sidecar, but editing a jpg does not. But if I reopen an edit jpg after cropping it, for example, I still have the ability to recrop and open the picture to its original dimensions. How is that possible? If editing a jpg will permanently change it, how can I go back and where is the edited data kept, if not in a sidecar?

 

[clee01l]

I've been playing around with Lightroom for the first time, considering moving from Classic. But here's a mystery: I understand that editing a raw file creates a sidecar, but editing a jpg does not. But if I reopen an edit jpg after cropping it, for example, I still have the ability to recrop and open the picture to its original dimensions. How is that possible? If editing a jpg will permanently change it, how can I go back and where is the edited data kept, if not in a sidecar?

Lightroom creates a XMP block of data In a Proprietary RAW file this is written as a sidecar file and stored separately. The JPEG format has a provision for storing the XMP block in the JPEG header. Lightroom writes the XMP there but does not change the original data block.

TIFF and DNG are also non proprietary filtering formats that can have an XMP section.


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[rwest01]

Lightroom creates a XMP block of data In a Proprietary RAW file this is written as a sidecar file and stored separately. The JPEG format has a provision for storing the XMP block in the JPEG header. Lightroom writes the XMP there but does not change the original data block.

TIFF and DNG are also non proprietary filtering formats that can have an XMP section.


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Thanks so much- that makes sense. So a follow-up, general question: Does this mean that all LR edits are non-destructive, regardless of file format? And if so, do you know why Photoshop Elements and other programs don't use this method of storing changes rather than removing file info?

 

[Conrad Chavez]

…do you know why Photoshop Elements and other programs don't use this method of storing changes rather than removing file info?

They do and they don’t. They are two different models for editing software, and both are commonly used.

Photoshop Elements is based on Photoshop, and Photoshop is an old style editor like many others that came out in the 1980s to 2000s (The GIMP, Corel Photo-Paint, etc.). They work like Microsoft Office apps, where each document is opened individually into its own floating window, and destructively edited: Ending a session means rewriting the pixels in the original image, and it isn’t possible to return to earlier edits after closing the document.

Lightroom and Camera Raw use a model also used by apps designed more recently, like Apple Photos and many current mobile photo apps, and practically all video and audio editing apps. These applications apply edits parametrically: Instead of permanently altering pixels of the original file, edits are stored separately as changes to parameters (like Exposure or Sharpening) that are permanently applied only when exporting a copy. So the original image is never changed. Apps have been moving in this direction in the last 20 years because it takes a lot less storage space to store changes (they’re just parameter values), making them more cloud-friendly to sync for mobile devices, much easier and faster to batch-edit large shoots, and because it’s always possible to reverse out of all changes to the original file at any time in the future. Which is great when, for example, you would like to reprocess a 15-year-old raw file to a higher quality by using new features that were not available 15 years ago.

There are advantages to both ways that the other way can’t match, which is why Adobe holds on to both their direct pixel editors Photoshop and Photoshop Elements, and their parametric editors Lightroom and Camera Raw.