When blending composite landscapes, it can be incredibly tricky to mask the exposures perfectly, even when the tripod isn’t touched between exposures. Luminosity masking is a radically powerful technique to create ultra-precise masks in a matter of minutes.
The term “composite” is pretty vague: it can refer to an image that is completely fabricated, or to more innocent techniques like focus stacking. In this post processing series, we’re blending exposures of the exact same spot and composition taken over a 3 to 6 hour period: one from golden hour, blue hour, and astronomical twilight.
Exposure blending — or “blending moments in time” as Elia Locardi calls it — is a technique that’s probably familiar to you or many of the landscape photographers you follow. Unlike fabricated composites, the process of blending exposures from the same scene is much more forgiving: you can typically use a soft mask to smoothly transition between exposures.
But that’s not always enough. Particularly when blending in star trails, the mask on top of the base exposure has to be flawless, which is particularly difficult because of the harsh transition between sky and mountains at blue hour. Even when the exposures are perfectly aligned, the edge will have a strong white border.
How can you make a crisp transition without a visible white outline? That’s where luminosity masking comes in: it’s a technique to guide the masking process and map brightness to opacity. Rather than spending hours to make a precise selection, in a matter of minutes you can turn the image’s luminosity into a selection that guides your rough selection.
It’s still critical to precisely align the exposures non-destructively so you can adjust ACR settings later, so if you missed the first part of this series on creating composite landscapes, make sure to catch up:
Have you used luminosity masking before? Especially for more complex landscapes, what are some of the challenges you’ve encountered?