You use External Editing preferences to specify the file format and other options for editing camera raw and DNG files in Photoshop Elements and external image-editing applications that cannot read the mosaic sensor data in camera raw files. The options that you specify in External Editing preferences are also used by Photoshop when you save camera raw and DNG files from Lightroom Classic CC in Photoshop. Finally, you also use External Editing preferences to select external image-editing applications.
Lightroom Classic CC opens camera raw and DNG files directly in Photoshop CS3 (10.0.1) or later. However, Lightroom Classic CC must send either TIFF or PSD copies of camera raw and DNG files to Photoshop Elements and to other external editors that cannot read raw data. In the External Editing preferences, you specify the file format, color space, bit depth, and compression for the TIFF and PSD files that Lightroom Classic CC sends to these editors. To best preserve color details in photos sent from Lightroom Classic CC, 16-bit ProPhoto RGB is recommended. If you open camera raw files from Lightroom Classic CC directly into Photoshop and save them there, Photoshop uses the settings you specify in Lightroom Classic CC External Editing preferences for the files that it saves.
Saves camera raw images in either TIFF or PSD format. See Supported file formats.
Converts photos to the sRGB, AdobeRGB, or ProPhoto RGB color space and tags them with the color profile. See How Lightroom Classic CC manages color.
Saves photos with a bit depth of 8 bits or 16 bits per color channel (red, green, and blue). Files that are 8 bit are smaller and more compatible with various applications, but do not preserve the fine tonal detail of 16-bit files.
(TIFF only) Applies either ZIP compression or no compression to photos. ZIP is a lossless compression method that is most effective for images that contain large areas of single color.
Uses the template you specify to name the file. Select a template and specify custom text or the start number of the filenames. See The Filename Template Editor and Text Template Editor.
You can designate an application to be used as an external editor in the External Editing preferences dialog box. After you choose an application, you can always use Preferences to change to a different application.
You can also select an external editor by choosing Photo > Edit In Other Application from the Library or Develop module. You’ll be prompted to navigate to and select the application to use. After you choose an external editor, the name of the application appears as Edit In [Name of Application] in the Photo menu.
You can create presets for external editors in the External Editing preferences dialog box. External editor presets allow you to specify multiple applications as external editors and create different photo-handling options for multiple uses with one or more external editors.