Today’s Question: I have seen instructors illustrate the use of a Linear Gradient [for a targeted adjustment]. But instead of starting the gradient at the edge of a side of the image, I’ve seen the gradient begun lower or higher than the edge, though it appears the effect is the same as beginning the gradient at the top or bottom of the image. Is that correct?
Tim’s Quick Answer: Not exactly. Starting or finishing the gradient beyond the edge of the image will impact the degree to which specific areas of the image are affected by the targeted adjustment. For example, there might be no portion of the image that is getting the full effect of the adjustment, no portion of the image that is getting none of the effect, or both.
More Detail: You can use a linear gradient as the basis of a targeted adjustment with many software tools, including Photoshop, Camera Raw, Lightroom, and Lightroom Classic. The basic idea is that the linear gradient causes an adjustment to affect one side of the image completely, the opposite side won’t be affected at all, and there will be a smooth transition of the effect between the two. The two “sides” of the image can be in any direction, such as top to bottom, left to right, or one corner to another.
The linear gradient used in this manner is often presented as a white-to-black gradient, where white represents the area of the image being affected completely by the adjustment and black represents the area not being affected. The transition of shades of gray in between represents the transition between the two areas.
Let’s assume a situation where you’re focusing an adjustment on the sky but not the lower portion of the image. Based on the white-to-black model, a typical gradient for this targeted adjustment might involve a gradient that is white for the upper third of the image, a gradation from white to black for the middle third, and black for the lower third of the image.
However, you can also have the gradient start outside one or both edges of the photo. Let’s assume both ends of the gradient start outside the image area. This would involve a gradient that doesn’t go from white to black, for example, but from a light shade of gray to a dark shade of gray.
In this example, there would be no portion of the image getting the full effect of the targeted adjustment if none of the gradient mask is white. There would also be no area of the image that was not affected by the adjustment at all, since none of the gradient mask is black.
In many ways this is just an academic issue. For example, if none of the image is getting the full effect of the adjustment, you can simply make the adjustment stronger. But the point is that where the linear gradient starts and ends does impact the overall effect on the image.
