Today’s Question: Is there a difference between the Overlay and Soft Light blend modes in Photoshop? I see some people using one versus the other with the same basic techniques.
Tim’s Quick Answer: The Overlay and Soft Light blend modes are both “contrast” blend modes that enable you to achieve both a brightening and darkening effect with an underlying image at the same time. The effect of both is essentially the same, with the difference being that the Overlay blend mode creates a somewhat stronger effect than the Soft Light blend mode.
More Detail: The first three categories of blend modes in Photoshop enable you to apply a darkening effect (with Multiply being the first of these blend modes), a lightening effect (with Screen being the first of these blend modes), or both (with Overlay being the first of these blend modes).
I refer to the blend modes that can both lighten and darken as the “Contrast” blend modes. There are a variety of situations where you might use a contrast blend mode, such as dodging and burning by painting onto a separate layer or reducing haze and enhancing detail with the “High Pass” sharpening technique.
With a contrast blend mode, any pixels on the layer to which you have applied the blend mode that are lighter than middle gray will have a lightening effect on the underlying image. Any pixels that are darker than middle gray will have a darkening effect on the underlying image. So if you have both light and dark areas in the layer you’ve applied the contrast blend mode to, you’ll brighten some areas and darken others, leading to (generally speaking) increased contrast.
The Overlay blend mode simply applies a stronger effect than the Soft Light blend mode. Thus, some photographers prefer one over the other. I, for example, prefer the Overlay blend mode because it provides a stronger effect.
It is important to keep in mind, however, that with many of the techniques where you might employ a contrast blend mode, you’re going to reduce the Opacity setting for the layer to which the blend mode is applied. Therefore, the final effect can be the same with either Overlay or Soft Light, with the only difference being the specific Opacity setting you use to achieve the final effect.
In general you can think of the Overlay and Soft Light blend modes as being interchangeable. Just keep in mind that the Overlay blend mode provides a stronger contrast effect than the Soft Light blend mode.