In Adobe Photoshop, you can see what a shadow is made of. A shadow is a light source that appears in the dark areas in the image. We can say that a shadow is the darkness between two light areas. So if you want to show the shape of the eye of an subject, you can create a shadow by using a black and white photograph and copy it to a layer, or you can create a natural light shadow using a white background and copy the photo to the same layer. Find the photo If you are creating a fake shadow using a Photoshop photo, you have to find a natural shadow of the eye that you want to use. If you are doing a realistic look, you should not use a photo of someone’s eye. If you are trying to imitate an eye, then try to find a photo of an eye using a camera.
https://www.academia.edu/52372690/How_to_Add_Realistic_Shadows_to_Images_in_Photoshop
https://www.slideserve.com/kristofferwins2/how-to-create-realistic-shadows-to-images-in-photoshop
