Two ways to adjust image tone and color are to use adjustment layers or to edit in Adobe Camera Raw. Both offer a wide range of control and flexibility, without permanently altering or damaging the original image information. The integrity of your original images is preserved. This nondestructive editing gives you the flexibility to make further changes, start over with a different editing approach, or undo the adjustments even after you've saved the edits.
With adjustment layers, you apply edits on a separate layer in the image file, leaving the original image (background layer) intact. The easiest way to access the adjustment layer tools is clicking an icon in the Adjustments panel. You can add more than one adjustment layer for more complex image editing. You can also use a mask to apply the adjustment to a specific part of the image. For more information, see Masking layers.
Adobe Camera Raw is a Photoshop plug-in for making color and tonal adjustments. In its editing window, there is a large preview image and the adjustment tools are laid out in the order that you would normally use them. Despite its name, Adobe Camera Raw can edit JPEGs and TIFFs in addition to camera raw files. If you want to apply the same adjustment to multiple images, you can save the settings as a preset and apply as needed.
Unless a specific adjustment isn't available as an adjustment layer or in Camera Raw, don't use the commands in the Image > Adjustments menu. The adjustments under the Image menu permanently alter or delete pixel information in your image.
Use the controls in Adobe Camera Raw to adjust the settings. You can use the Adjustment brush to apply edits to specific areas of the image. For more information, see Make color and tonal adjustments in Camera Raw.
You can set preferences to always open JPEGs and TIFFs in Camera Raw.
Tip: For tips on setting your JPGs to open in Adobe Camera Raw, see this tutorial video by Terry White.
In addition to the two workflows described above, you can also use Smart Objects for editing layers nondestructively. See Linked Smart Objects for more information.