Layers Opacity and Fill

In this part of the chapter, I’m going to explain the difference between two very useful features in Photoshop; these features are opacity and fill you can find these features as slides that you can control in the layers palette.
What is the difference between these two features?
-Opacity: this feature will help you set and adjust how opaque the layer you created and all it’s content as well.
-Fill: this feature will help you set and adjust the opacity of filled shapes that you created in the layer.

Here is 2 images, one with the green box layer's opacity and fill are set to 100%, in the second image they are set to 50%. Just to give you a hint on how the opacity and the fill work:

Image 1

Image 2