For non- destructive editing, you can't beat Adjust Layer for ease of use and flexibility. Here, we explain the basic to using these invaluable layers so you can be more selective with your editing.
Before Adjustments Layer were introduced photographers would have to duplicate the background layer to avoid editing or damaging the original image. While you can still do this, Adjustments layer allow you to apply adjustments like curves, Levels or hue/saturation as a separate layer that you can refine, changes or delete at any time during your editing process. The alternative would be to apply an adjustments command via Image>Adjustments directly to a duplicate image layer, but this won't give you the flexibility of editing the effect after you have committed to it. Plus, if you want to get rid of the adjustment's effect, you will have to delete the whole image layer, which can be frustrating if you have applied the different adjustments to the image layer you need to delete it.
Most of the usual Adjust command is available as an adjustment layer making it a much more favorable way to edit the picture, but it's still worth checking out the adjustments menu for those commands you cant access as a separate layer. Being able to control how an adjustment affects your image post-application means you are not committed to any adjustment command you use, making the process a lot more forgiving and fluid. Not only you can reverse or delete an-adjustments, you can temporarily hide them the same way you would an image layer, you can apply a blending mode or fine-tune the effect by changing the opacity and you can restrict the effect using the layer mask.
An Adjustments layer can be created in one of the three ways: by clicking Layer>New Adjust Layer and selecting your required adjustments, clicking on the adjustments icon (Half black/half-white circle) at the bottom of the layers palette to access the same list of options or by opening the adjustments panel via the window menu. Any of those work, but some are quicker than others and offer you more options: You just need to find the one you work with the most efficiently.
Adjustment Layers Panel
By opening the Adjustments panel, you get immediate access to all adjustments presets and the 15 core adjustment layer at the clicking button. When you select an adjusting layer from the panel, the adjustments panel converts into a control panel for the command with the tools to refine the effect. Click back on to the layers palette to close and convert the control panel back to the adjustments panel. Have a good to see what we mean...
1) Add an Adjustments: Clicking on the half white/half black icon at the bottom of the layers palette to access adjustment layers. Click on the adjustments you want to apply.
2) Presets: Click the drop-down menus of each of the adjustment layers to access their loaded presets. normally located at the top of the specific adjustments layer control panel.
Adjustment Layers Panel
3) Expand View: Click here to enlarge the Adjustments panel. It can be useful if you are working with curves or levels and need a larger area to view the adjustment graphs.
4) Review: If you are editing an adjustments layer, click and hold this button to revert back to the adjustments layer original state to see whether your editing has improved or worsened the overall effect of the image.
5) Reset: Click here to reset the adjustments layer back to it's default settings.
6) Layer Visibility: Click on the eye to temporarily switch off the adjustments layer. It's useful to toggle between visible and invisible to see the effect of the adjustment layer on the original images.
8) Delete: click the trash can to delete the current adjustments layer.