Image Effects: Desaturation Vignette

One of the most time-consuming but most enjoyable tasks I perform regularly with Beer Busters is editing, formatting and posting blog articles. The vast majority of content I work with is created by others; I just polish it and get it up on the interwebs. This includes photos. These photos are often taken with an iPhone, rather than a fancy high-end camera, and are taken under less than ideal conditions for a perfect photograph. So, through my attempts to jazz-up these pics for presentation, I’ve settled on a few techniques that are my go-to methods.

Desaturation Vignette

In case you are not familiar (or have never watched a Blender tutorial by Andrew Price), vignetting “is a reduction of an image’s brightness or saturation at the periphery compared to the image center” (Wikipedia). This effect can be the result of several factors, including filters, secondary lenses, multiple element lenses and anything that essentially causes the light at the periphery of a field of view to be dimmed compared to light in the center. It is radial in nature because lenses are, after all, convex and circular. We think of photographs as being rectangular (and they are, obviously) but that’s because the film plane is rectangular and records a section within a circular image projected by the lens. Often, this effect is undesirable and occurs unintentionally. However, many photographers and digital artists intentionally introduce vignetting or add it in post-production.

Vignetting, from a Nature Academy tutorial
Vignetting, from a Nature Academy tutorial

Some would say – myself included – that this effect is often overused and added unnecessarily. Though, it can be a great effect. (I dig on Andrew Price but he does some fantastic work and, to be fair, doesn’t use much vignetting these days.) In most cases, however, the effect is used to darken the edges of an image. But, as Wikipedia told us up there, it can also desaturate the edges, which can be a more subtle and more interesting effect. Achieving this in just about any image editing software is fairly simple. Here, I will describe how to do it in GIMP. There are other methods to achieve this result. However, the technique described here is non-destructive and, as such, is more flexible to alter. (The photograph used in this tutorial was taken by Steph Heffner.)

When you load up a photograph in GIMP you’ll have one layer. First, simply duplicate that layer.

Duplicate the background layer
Duplicate the background layer

Then, with the top layer selected, go to Color -> Desturate. This will bring up a dialogue box with three options: Lightness, Luminosity and Average. Pick whichever one looks the awesomest.

Lightness, here, is the awesomest
Lightness, here, is the awesomest

Now, right click on the desaturated layer in the layer stack and choose “Add Layer Mask” from the menu. This brings up another dialogue, choose the “White (Full Opacity)” option. A white square will appear next to the thumbnail image of the layer in the layer stack. This is a representation of the layer mask, which is essentially a one channel (grayscale) image. It’s completely white, meaning every area of the layer is visible (not masked).

Add mask to desaturated layer
Add mask to desaturated layer

You can paint in greyscale on the layer mask, altering the opacity of the layer. White areas of the mask are fully opaque, black areas are fully transparent and tones in between are semi-transparent. This is a non-destructive edit; the original data of the desaturated layer is still there. So, at this point, you can use any number of techniques to desaturate any area of the image you want.

But, to create the vignette effect, this is what I most often do. First, under the view menu check “Snap to Canvas Edges” – this is usually off by default. This causes things to, unsurprisingly, snap to the edges of the canvass.

Set snapping to canvas edges
Set snapping to canvas edges

Then create an elliptical selection over the entire image. Now, depending on the degree to which you want the desaturation to extend inward from the edges, you can shrink the selection. To do this, under the Select menu select “Shrink”. A dialogue box will appear in which you can enter the amount of shrinkage in a number of units. (That was, unintentionally, a rather amusing sentence.)

Shrink the selection
Shrink the selection

I do this because it keeps the selection centered and allows me to define the size of the selection numerically, which can be useful when applying a similar effect to multiple similar images. This method also keeps the aspect ratio of the selection the same as the image. However, you could alternately set guides to the horizontal and vertical centers of the image then create the selection by starting at the center of the image and growing outward. If you hold CTRL while making a selection, it expands from the center.

Hold CTRL to expand selection from center
Hold CTRL to expand selection from center

So this selection will define the boundary between the desaturated edges and the fully saturated center. Of course we want the transition between the two to be subtle and gradated. To accomplish that, we simply feather the selection by choosing Select -> Feather. Now we have another dialogue box where we define the amount of feathering.

Feather the selection
Feather the selection

Next, simply fill the area of the selection with black using the paint bucket tool. Make sure you are still editing the layer mask, not the layer contents, by clicking the layer mask thumb in the layer stack.

Fill the selected area of the mask with black
Fill the selected area of the mask with black

Viola, as they say. In most circumstances you won’t want the edges to be completely desaturated (subtlety, as always, is your friend.) So you can simply adjust the layer opacity of the desaturated layer to mute the effect.

Adjust opacity of the desaturated layer
Adjust opacity of the desaturated layer
The final result
The final result

Of course, you can use this technique for a variety of effects, not just desaturation:

Darkened vignette
Darkened vignette
Radial blur
Radial blur
Soft Glow
Soft Glow

You can use this effect to give some subtle highlight to any area of an image you want to bring focus to. If, for example, you want to highlight a subject that happens to not be in the center of the frame, you can simply adjust your selection area accordingly.

Thanks for reading, be sure to keep an eye out for more image effect tutorials coming soon.