How to Remove Shadows With Frequency Separation

If you’re looking to take your retouching skills to the next level, you should familiarize yourself with Frequency Separation and how it can help you with various photo editing tasks. One of these can appear in cityscape and architectural photography. Especially during the blue hour and at night you can get unwanted shadows on your photos. In this article I will explain how to remove those with frequency separation.

The photo in the before and after comparison may look familiar to you. I recently published an article on how to improve blue hour photos by introducing a vignette in the sky. I also had to deal with a shadow cast by one of the streetlights behind me in this photo. This shadow unbalanced the composition, and an initial attempt to hide it by introducing a vignette to the foreground failed miserably, as I explain in the feature video.

A better way to deal with this is to completely remove the shadow through skillful retouching. One way to do this is to use curves and lightness masks to lighten only the shadow areas. The problem is that this technique also lightens some of the structures that should remain dark if you’re not careful. Multiple adjustments targeting different tonal ranges can help, but I prefer a different approach.

Frequency separation to remove shadows

In a recent article, I shared one use of frequency separation. I used it to remove footprints from the sand in a desert photo. The principle is the same for shadow retouching. First, separate the fine details from the details you want to retouch. The shadow in my example looks blurry. It’s at a low frequency. The fine structures of the street’s cobblestones, on the other hand, have a high frequency.

Whenever you use frequency separation in your editing, the first task is to isolate the details you want to retouch from those you want to leave intact. The steps to create the frequency separation layers are the same as in my article on editing the desert photo:

1. Make a merged copy of your edit by pressing and holding Ctrl/Cmd + Alt + Shift + E and rename to “low”.

2. Copy this layer and rename the copy “high”.

3. Choose the lower level and go to it Filter – Blur – Gaussian Blur… . Use a radius big enough to blur the details you want to separate from the shadow. This blurred layer should still show the shadow but not the structures hiding in the shadow.

4. With the high level selected, go to Image – Apply Image… and choose the following settings: Make the low layer the source; activate the Turning back check box; set to Mix to Add to, opacity to 100%, scale to 2 and offset to 0. These settings only work for 16-bit images. For 8-bit photos, disable that Turning back box set Mix to Subtractand paste a offset from 128. The scale stay with 2.

5. Set the blending mode of high shift to linear light.

In the feature video, I show how to use a combination of cloning, dodge, burn and a color layer to eliminate the shadow and some lens flare caused by the city lights. I also talk about the mistake I made with the vignette on my first try to hide the shadow.

Clone

To apply cloning in a non-destructive way, create a new layer above the low frequency layer and use the Clone Stamp Tool put sample Current & below to remove the shadow. By holding down Old You can sample details from an adjacent area by clicking on it. Then let go Old Key and paint over the shadow area. You can hide the high frequency layer while doing this task.

Typically, the low-frequency layer still contains structures and contours. Try to align the sampled details with those you retouch before you start painting. You don’t have to be 100% perfect with the alignment as I show in the feature video. The blurred layer you’re working on is pretty forgiving. You don’t have to paint at 100% either. Using low opacities of 50% or less and building up the effect can help you get the best result.

dodge and burn

A… create soft light Layer over the low frequency layer and use it to lighten the shadow by painting with a soft, low opacity white brush. With a black brush, darken areas around the shadow for a smoother transition. It helps to combine this technique with the clone layer.

An alternative to a dodge and burn layer are curves adjustment layers, which allow you to lighten and darken specific areas. And if you want to be super precise, use luminance masks to target just the shadow.

fix colors

A layer set to blending mode colour can be helpful if there are color shifts in your photo due to shadows or lens flare. Try a color with the pipette from a clean area and draw over the shadow or lens flare inside the paint layer. It removes all color shifts in these areas. Combine this technique with cloning and dodge and burn for best results.

Conclusion

As you can see, the right combination of post-processing techniques in Photoshop can help you fix many problems. However, if possible, try to avoid such mistakes in the field. In my case, there was no position to place my camera where I could have avoided the shadow without affecting the composition. But in many cases just moving the camera can solve the problem.

You may also be wondering what to do with the high frequency layer. When retouching shadows or footprints, there is no need to work on the fine details. All adjustments are usually focused on the low frequencies of the photo. But there are situations where you want to aim for the higher frequencies. An example of this is the removal of chromatic aberrations and color fringes.

And there are certainly more ways to use frequency separation. Let’s hear about your favorite use case in the comments below.