“Ask Jason” – What’s the Difference Between Opacity and Fill?

Welcome to the first of what will hopefully become a more regular series here on the blog. I invite you, my readers to send in questions about Photoshop and digital photography that I may address them here. No question is too small and the learning process of such a deep and complex program such as Photoshop and Lightroom is an ongoing endeavor. As I’ve mentioned before, I work from the philosophy that when I learn something about Photoshop I want to share it so that you can learn more too. So please, ask away!

To start us off, here is a question I received from a reader the other day:

Jason,

I’ve been trying to distinguish between Opacity and Fill. As an experiment, I created two layers, black over white. I then adjusted opacity to 50%, flattened and measured the color of grey (r=g=b=128). Repeating the process but adjusting fill to 50% gave the same results. What’s the difference and when would I prefer to use one over the other?

Thanks,
Steve

What Steve is asking is actually a fairly common question and even some more advanced users aren’t quite sure how it works or when to use it. In fact, I asked a couple of my fellow designers in the graphics department at work and they didn’t really know what it was for. So, Steve, you’re in good company!

So we all know what we’re talking about, in the upper right corner of the Layers Panel you will see two boxes, one for Opacity and one for Fill and it is very easy to assume that they both do the same thing.

Before getting into a discussion about Opacity vs. Fill, I want to make a distinction that has always helped me to understand what’s going on here. The distinction is between a layer and the contents of the layer. A layer is the row within the layers panel on which you can add objects such as shapes, text, images, drawings, etc. The contents of the layer are those things (text, shapes, etc.) that are on the layer. Simple enough, right? But this is a very important distinction. You do not apply layer effects to a specific object on a layer, you apply the effects to the layer as a whole. Which brings us to the question at hand.

Opacity, as I understand it, acts on the layer – the contents and the effects – while Fill acts only on the contents and leaves the effects alone.

To illustrate this, on a new layer, make a square of any color you like. Next, apply a decent sized stroke to it (inside, outside, color, whatever you want to do) and click Ok. Duplicate the layer and move the square so they are next to each other. Now lower the opacity of one of the  layers to 50% and you will see that the square and its stroke are now more transparent. Select the other square, but this time, lower the fill to 50% and you will notice that only the square, not the stroke, is semi-transparent while the stroke is still fully opaque.

Most of the time adjusting the opacity slider along will do the job for you and you don’t have to worry about fill. However, when using layer effects you may want to play around with the fill to give yourself more options. For example, if you want to have text that is only an outline, add a stroke and lower the fill. If you want to create a semi-transparent box to hold some text in your design, create a black box, add a drop shadow that has a distance of zero and a decent size, lower the fill to about 20% – or whatever works for you – and there you go.

So, in a nutshell, Opacity affects the layer, Fill affects the objects on the layer and this really comes into play when using Layer Effects. Play around with it and I’m sure you’ll get the hang of it in no time! Do you know of another way of explaining the difference? What helps you remember? Are there other uses for Fill that you’ve come across? Please share them in the comments!

If you have any Photoshop questions, please send them along and you may soon find the answer here! Don’t be shy, I’m sure you’re not the only one wondering the same thing. By asking your questions, you’ll be helping others to understand and use Photoshop better too.

Leave a Comment: