In photography, the difference between brightest and the darkest areas is known as dynamic range. Our camera cannot capture it as good as our eyes see when there are very bright and very dark coloured objects in our images.
Take this fruit bowl as an example:
If you expose for the fruits, the details on the dark wooden bowl are lost. But, if you expose for the bowl, the green grapes and the apple are over-exposed i.e. too bright.
We will now see how to overcome this problem with exposure blending:
The general steps in any photo-editing software are as follows:
- Open the over-exposed photo in the software. This will open it as the background layer.
- Open the correct exposure photo as a layer. This will place it as a top layer on the over-exposed background layer.
- Add a layer mask and initialize to White (full opacity). This means that only the top layer is visible.
- Using the paintbrush tool, paint on the fruit bowl with black colour to “erase” or remove it from top layer. Now the background layer with brighter fruit bowl is seen.
- Black colour removes the top layer and white will bring it back. So, if you erase more than you should have by mistake, then you can use the white paintbrush to undo those areas. You may have to zoom in to accurately remove the top layer in certain places.
- Export to save as a JPG or ‘Save As’ to keep the layers if you want to return to it to edit again in the future.
We will now see how to do the above steps in GIMP which is a free photo editing software:
- Over exposed background: Click on the GIMP icon to open the software. Go to File -> Open -> open the overexposed photo.
- Original top layer: Go to File -> Open as Layers -> Original photo with correctly exposed fruits and dark wooden bowl.
- Layer Mask: Right click on top layer and select ‘Add Layer Mask’. In the dialog box that opens, make sure the ‘White (full opacity)’ radio button is selected.
- Paint with black to remove part of top layer: Select the paintbrush tool. Make sure that black is the foreground colour. Remember, painting with black reveals bottom layer! Select round brush and change hardness to 005. Increase brush size to whatever is convenient to you. I have used 195 here. Now you will see the cursor has changed to round shape. Paint on the dark area to be lightened.
- Zoom and edit to make accurate changes: You can see that I have erased more than required on the right side. Go to View -> Zoom ->Zoom In to zoom as much as you want. I had to do it a couple of times to get to the right size. Use the scroll bar horizontally and vertically to get to the area you want to change. Swap the foreground and background areas. Now white is the foreground colour with which you can paint. Bring back the areas which should not have been removed. Alter brush size if required.
- Save as JPG or XCF: You can save it as a JPG file which will merge all the layers. Do this if you are sure you will not need to edit this file again in future. Or you can save it as a file with XCF extension which in GIMP will preserve the layers, so that if you have to edit the file again in future, you will not have to do all this work again.
- Save as JPG: Go to File ->Export. In the next dialog box, give the file a suitable name and click Export. Save with Quality 85 or higher.
- Save as XCF: Go to File ->Save As. Give a suitable filename and Click Save.
That’s it! You have managed to do exposure blending in GIMP! Note: I have not used two separate clicks from the camera. The original file was shot in RAW format and the over exposed photo is from the same original photo. So, you can see that photos can be edited for proper exposure even after you have completed shooting!
Have you found this article helpful? Do you know of other methods to achieve proper exposure in post processing? Please leave a comment, I’d love to hear from you!