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In landscape photography, it is usually desired that the whole image, from the foreground elements to the mountains rising in the distance are all perfectly in focus. But maximizing depth of field like this isn’t easily achieved, especially if you don’t want to loose any quality due to having to use the smallest aperture available.
Remember, your lens is probably at it’s sharpest somewhere between f/5.6 and f/11 (depending on min. aperture) and having to use a really narrow aperture like f/22 will reduce the quality of the image due to diffraction. I won’t bore you with technical details and quantum physics, which isn’t my strong suit anyway. The gist of it is though that yes, at f/22 you’ll technically get more of it in focus, but with an aperture this narrow, light passes through a much tinier hole and starts to interfere with itself. And boom, you get a softer image.
Here’s where focus stacking comes in. This isn’t as difficult, time-consuming or laborious as it sounds and just requires you to shoot multiple images in the field and spend some additional time in post processing. What you are doing is basically take multiple photos of the exact same scene, but they all have the focus in different areas. Eventually these images get blended together into one photo that uses the sharpest portion of each image and is tack sharp all over.
All in all, focus stacking is easily done and yields far sharper results than are possible with only one exposure. It is most often used in macro photography and landscape photography done with zoom lenses, but also comes in very handy in wide-angle situations with a very close foreground object. You don’t always have to focus stack, in most situations you’ll be fine without it, but it’s a very useful trick you should know nonetheless.
In my example I’m going to use a sunset image from Guadalupe Mountains National Park in Texas. As you can see, I wanted both the cactus in the foreground, as well as the mountain in the background in focus, but it just wasn’t possible with only one exposure. For simplicity’s sake, I decided to only stack two images, one with the foreground in focus and one with the background in focus. Of course you can do this with as many images as you deem appropriate for the scene though.
What you need:
- A steady tripod
- Your camera and lens
- Photoshop, Elements or a similar photo editing software. This tutorial focuses on Adobe Photoshop though.
Here’s What You Do in the Field:
1. Find the sweet spot of your lens
A good rule of thumb to finding your lens’s sweet spot is finding out what it’s maximum aperture is and stopping down 2.5 to 3 stops from there. For example, if the max. aperture of your lens is f/2.8, the sweet spot should be around f/5.6-f/8.
Have the camera on a tripod, as it is important that all images used have an identical composition and only the focus differs.
3. Use manual mode if your camera allows it
All images should have the same exposure settings, meaning shutter speed, ISO and aperture stay identical.
4. Manual focus by zooming in on the desired area
Start with the nearest part of your scene and set your focus to progressively further distances in the following images. Account for depth of field and make sure there is some overlap in order to have everything from very near to far in sharp focus. This sequence ends when you reach the furtest point, which should be near or right at infinity.
Here’s what you do in Post Processing
There are two ways you can blend your images together. One relies on Photoshop to select the appropriate spots to blend, the other lets you do just that manually.
Automated Focus Blending with Photoshop
1. File – Scripts – Load Files into Stack (This opens all your images as different layers in one Photoshop file)
2. After loading the files, I like to sort the layers from nearest to furthest focus and name them appropriately. Also, make sure all layers are regular layers and that no layer is labeled “background”. If that’s the case, double click it to turn it into a regular layer.
3. Edit – Auto Align Layers – select Auto (This makes sure that all your images are perfectly aligned)
4. Edit – Auto-Blend Layers – check Seamless Tones and Colors (Photoshop now determines the sharpest portions of each image and applies the appropriate layer masks)
5. You see the resulting layer masks popping up next to the layers with white showing the revealed, sharpest spots and black showing the hidden parts. If necessary, you can then zoom in, go over the image and manually correct anything Photoshop may have gotten wrong by painting over the relevant spot with either black (concealing) or white (revealing).
This is what I usually go for if I’m only blending together two or three images as I like having a bit more control and don’t mind giving up some time to get a more precise result. If you decide to go the manual route, follow steps one through three from above to ensure you open the files as layers and they align, but instead of automating the blending process, stack the images using layer masks and white/black gradients or brushes.
There you go guys, it’s as easy as it sounds. And after the focus stacking is done, you can then continue to edit the photo as you normally would.