What’s the Difference Between Flow, Opacity, and Fill In Photoshop?

When working in Photoshop, you might be familiar with the difference between Flow and Opacity, but how does Fill change things and what can it be used for? Check out this informative video to learn how they work.

Unmesh Dinda of PiXimperfect has put together an excellent outline of how these aspects of Photoshop function and why you might want to use each one for different purposes.

Even if you’re familiar with the difference between Flow and Opacity, you might now be aware of what Fill does and where it becomes useful. In terms of controlling layers, both Fill and Opacity will control the opacity, so what is Fill for? Essentially, it separates any effects on a layer — drop shadow, emboss, gradient overlay, etc — from the rest of the layer’s contents, as perfectly demonstrated by Dinda. While this is a nice effect if you’re adding text, it’s not necessarily that useful if you’re simply editing a photograph. However, things change when you start controlling the Blend Mode of a particular layer. For example, if you added a layer of solid color to a photograph and switched the Blend Mode to Multiply so that it only affects the highlights, you’ll find that changing the Fill percentage will have a noticeably different result to changing the Opacity.

How do you use Fill in Photoshop? Let us know in the comments below.

Andy Day's picture

Andy Day is a British photographer and writer living in France. He began photographing parkour in 2003 and has been doing weird things in the city and elsewhere ever since. He's addicted to climbing and owns a fairly useless dog. He has an MA in Sociology & Photography which often makes him ponder what all of this really means.

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