Before you duplicate a layer you should always ask yourself: Can I do the same thing with adjustment layers. I’d say almost 90% of the time when using blend modes you’d be better off using adjustment layers instead of duplicating the layer and then applying the effect.
Here’s an example of what not to do. This is a video tutorial on You Tube showing you how to whiten eyes and teeth.
Obviously I don’t have the same images so I took a picture of my son and apply the same effects plus one more to make the eyes pop even more.
Here’s the picture without any editing. The whites in the eyes look a bit drab. The actual file size of the image on disk was 2.32MB. Opened in Photoshop it becomes 28.8MB
If I were to make a duplicate layer look at the file size increase!
Now if I remove the duplicate layer and apply a curves adjustment layer to the image look at the change! It’s identical!
If you apply the screen blend mode you will see the exact same effect as you would have if you applied the screen effect to the duplicated layer. Let’s do it now.
As you can see the blend mode also doesn’t add any size to the image.
Much like the video shown above if you make a black mask on the layer. (Hides everything) and then pain in the effect by using a white brush you can apply the screen blend mode to only the parts you actually want to use.
All the changes only added .9MB in total.
One more thing you can do to really make the eyes pop is by adding a little contrast. Again you can do it with blend modes. Softlight generally gives good contrast results that you can dial back.
Apply a Warming filter Adjustment layer (85) to the image and then apply the blend mode “softlight”. Below is a Before and After of the Softlight applied above the screen blend mode layer.
AFTER (END RESULT)
Again notice the file size is only up to 30.6MB