Simple Silhouette Double Exposures in GIMP
A very simple tutorial for creating a simple silhouette or portrait double exposure using the open-source image editor GIMP. GIMP is free to download and use on Windows, Mac & Linux systems, and is a good alternative to Photoshop. Download it here.
All you need for the following tutorial is a computer with GIMP installed and two photographs. For the best results, take your silhouette or portrait picture in front of a well-lit white wall. Good backgrounds to play around with might include trees, cityscapes, or textured photos of water or brickwork. For this example I have used a simple self-portrait I took against my living room wall and a photo of bare winter tree branches against a grey sky. The images are the same size (un-cropped, as if straight out of camera), which makes layering them very simple.
Once you have chosen your two images, you need to open GIMP and import the images as layers. To do this, go to ‘File’ which is on the navigation bar on the top left, and scroll down to ‘Open as Layers’. Find the images you wish to use, holding down your ‘Ctrl’ key to select multiple images.
At this stage it’s important to check the order of your layers. For this tutorial to work, you need to make sure that your textured layer is at the top of your layers stack. If it’s not, simply drag and drop it at the top of your stack.
Next, you need to make your textured layer transparent. This is so that you can erase parts of this layer in a later step to achieve a neat outline for your final image.
To make your textured layer transparent, right click on it in your ‘Layers’ panel (if your layers panel is missing, use ‘Ctrl+ L’ to open it). An options panel will appear, and you need to scroll down to the bottom and select ‘Add Alpha Channel’.
This is where the fun begins. In order to blend the two layers, select the textured layer in your layers panel (by left clicking on it) and at the top where the panel reads ‘Mode: Normal’ scroll down to ‘Lighten Only‘. You should now see your two images begin to merge.
Repeat step 3, but for the silhouette or portrait layer. However, instead of selecting ‘Lighten Only’, select ‘Overlay’.
At this stage you will notice that the textured layer (in this example, the tree branches) shows through quite clearly on both sides of the portrait. There’s nothing wrong with this if that’s the effect you’re going for. However, if you’d like to achieve a clean outline, you need to make a few adjustments.
Select the portrait layer in the layers panel, right click, and select ‘Duplicate Layer’. This creates an additional, overlay version of your portrait layer which darkens the portrait and cleans up a large part of the excess textured layer (the branches, in this example). Not all of it though. For the final touches, we need to use the ‘erase’ tool.
This step is optional. At this stage, you may like to adjust the opacity of each individual layer. For example, you may choose to make the textured layer slightly more transparent, or perhaps you’d like the portrait to be a little faded and ethereal. These are simple changes to make. Simply select the appropriate layer in the layers panel, and pull the opacity slider to the left or to the right to achieve your desired effect.
When you duplicated the portrait layer and added an overlay (steps 4 & 5) you largely cleaned up the outline of your final image. If there are small areas where the outline isn’t sharp and clean, select the ‘erase’ tool from your toolbox (if your toolbox is missing re-add it using Ctrl + B), and carefully touch up the edges of your silhouette.
Make sure that you have the correct layer selected before making these changes, otherwise you may find yourself erasing parts of your portrait or silhouette layer(s) instead! There are a few different options for the erase tool. You can select different brush sizes and shapes, and you may like to zoom in to get to the smaller details (‘View’ – ‘Zoom’).
You’re finished! To export your image from GIMP, return to the navigation bar at the top of GIMP – select ‘File‘ and scroll down to ‘Export’. You need to export rather than save, or your image will be saved as a GIMP file and not a jpeg.
There are so many options and possibilities for double exposure photography. It’s good fun to make them in camera on film as you never quite know how it’ll turn out, but editing images digitally gives you far greater creative control over the final image.
Once you’ve mastered the basic technique outlined in the steps above, you can try using multiple images, layer masks, gradients and much more besides. I hope to cover some of these in future GIMP tutorials.