Nondestructive editing allows you to make changes to an image without overwriting the original image data, which remains available in case you want to revert to it. Because nondestructive editing doesn’t remove data from an image, the image quality doesn’t degrade when you make edits. You can perform nondestructive editing in Photoshop in several ways:
Working with adjustment layers
Adjustment layers apply color and tonal adjustments to an image without permanently changing pixel values.
Filtering with Smart Filters
Filters applied to Smart Objects become Smart Filters and allow for nondestructive filter effects.
Adjusting variations, shadows, and highlights with Smart Objects
Shadow/Highlight and Variations commands can be applied to a Smart Object as Smart Filters.
Retouching on a separate layer
Clone Stamp, Healing Brush, and Spot Healing Brush tools let you retouch nondestructively on a separate layer. Be sure to select Sample All Layers from the options bar (select Ignore Adjustment Layers to ensure that adjustment layers won’t affect the separate layer twice). You can discard unsatisfactory retouching, if necessary.
Editing in Camera Raw
Adjustments to batches of raw, JPEG, or TIFF images preserve the original image data. Camera Raw stores adjustment settings on a per-image basis separately from the original image files.
Opening Camera Raw files as Smart Objects
Before you can edit Camera Raw files in Photoshop, you must configure settings for them with Camera Raw. Once you edit a Camera Raw file in Photoshop, you can’t reconfigure Camera Raw settings without losing the changes. Opening Camera Raw files in Photoshop as Smart Objects enables you to reconfigure Camera Raw settings at any time, even after you edit the file.
After you create a cropping rectangle with the Crop tool, select Hide from the options bar to preserve the cropped area in a layer. Restore the cropped area anytime by choosing Image > Reveal All or by dragging the Crop tool beyond the edge of the image. The Hide option is unavailable for images that contain only a background layer.