Today’s Question: I have a logo for my photography business that is black on a white background. What is the easiest way in Photoshop to mask out the logo so I can place it without the white background onto a photo like a watermark?
Tim’s Quick Answer: You can very quickly hide the white areas of the logo image by adding it as a layer to a photo in Photoshop and then changing the blend mode for the logo layer (using the popup at the top-left of the Layers panel) to the Multiply blend mode.
More Detail: With this type of situation you could obviously create a selection of the white areas relatively quickly, and then create a layer mask based on the selection. However, this would likely result in the edge of the logo having some fringing of white or gray areas, which could be difficult to clean up.
It would also be possible to use the “Blend If” controls described in an article in the November 2017 issue of Pixology magazine. However, this could create similar challenges with fringing (though that fringing would be easier to resolve with this method).
The beauty of using the Multiply blend mode is that it will help create a more seamless result with virtually no effort. This blend mode will cause white pixels in the applicable layer (the logo layer in this example) to become completely invisible. Darker pixels will cause a darkening of the pixels in the underlying image, with black pixels in the logo layer resulting in completely black pixels in the image below. Because of this behavior, shades of gray in the logo layer will result in a darkened area of the image below, which will result in a much smoother blending of any fringed areas along the edge of the logo.
Note, by the way, that for an inverted scenario (with a white logo on a black background) you could similarly hide the black pixels from the logo image layer by using the Screen blend mode in place of the Multiply blend mode.