FOCUS STACKING: CAPTURE CRITICALLY SHARP LANDSCAPES

You would think that with all the modern technology with cameras all we would need to do is set the lens to autofocus and press the shutter to capture a sharp image-you would think wrong. There are more things that you can do to capture sharp landscape images and here are three tips to get you started.

1. Use a sturdy tripod-carrying a tripod doesn’t have to be cumbersome and heavy, carbon fibre tripods are a lightweight answer. Apart from ensuring image sharpness, it will allow you to try special techniques such as focus stacking.
2. Use a cable or remote release-tripping the shutter with a cable or remote release removes the possibility of causing camera shake by pressing the shutter with your finger. You could even use the self timer, but this isn’t ideal when you are trying to capture a specific fleeting moment.
3. Use the optimal aperture-every lens has an optimal aperture or sweet spot where the image is the sharpest. You can easily find this by mounting your camera on a tripod perfectly parallel to a brick wall, then photograph it at each aperture. Check each image at 100% on your computer looking at the edge and centre sharpness. The one aperture that gives you the sharpest results is your optimal aperture for that lens. Each lens will differ, but generally f/8 to f/11 will tend to be the optimal.

Now combine all three of these tips along with a very easy technique called focus stacking and you will achieve critically sharp landscapes with subjects close to the camera right to infinity and beyond! Sorry I couldn’t resist. Focus stacking allows you to go beyond the capabilities of your equipment to capture pin sharp images. For example, take this image of the golden barrel cacti and agave. I wanted to accentuate the patterns and textures in this scene by using a 70-200mm lens to compress these shapes, but also wanted the image sharp throughout, but even stopping the lens down to f/22 to increase the depth of field did not achieve overall sharpness. In fact, shooting at f/22 softens the image through diffraction where light passes through a very small aperture such as f/22. Depth of field is not the same as image sharpness. So by using the optimal aperture of f/8 instead, I achieved the sharpest image possible by combining 12 images each focused at a different point in the scene. Focus stacking works great when nothing is moving in the scene such as this, but if there is any wind or moving elements then it could be more problematic. Let me take you through how to focus stack in the field, then how to combine the images in post processing.

I wanted to fill the frame with blooming heather with this image I made in the Peak District, so I set the tripod mounted camera close to the heather with Stanage Edge in the background. I’m using the Nikon D850 which automatically carries out the focus sequence so I will detail how to do this with the D850, but you can also do this manually with any DSLR by setting the lens to manual focus and turn the focus ring slightly until you have focused all the way through the scene.

1. Set a single focus point to the bottom of the frame using Live View. Make sure your auto focus is switched on.
2. In the Photo Shooting Menu, go to the last page to find Focus shift shooting. Go into the sub menu.
3. Set the number of shots-I generally have this set to 50 even though it will only shoot what it needs.
4. Set the focus step width-a value of 5 or less is recommended so it captures all the focus points. I set mine to 2 which will result in more images, but it will ensure that I get all the focus points. If you were to shoot macros then you would set this to 1.
5. Set interval until next shot to 0. Exposure smoothing ON and Silent photography also set ON.
6. Press start and let the camera shoot its sequence. (Tip-take a picture of your hand at the beginning and end of the sequence so you can differentiate it in post processing.)

It’s in the post

Now let’s combine all the images in post-production. You can do this using Photoshop, Helicon Focus or Zerene Stacker. I’ve used them all and have found that Zerene Stacker to be the best overall and best value for money. It produces no artifacts especially when there is a rise to the landscape. Because the physical size of the image changes as you change the focus, it tends to create artifacts along the top of the horizon such as with mountains. A great feature of the software is the retouching brush. This is especially useful when there are moving elements in your scene created by wind. This will create multiple subjects and if the clouds are moving fast you will have multiple edges to your clouds. In my scene here in the Peak District, the wind was blowing the heather as well as the sheep moving through the scene, but I’ll now show you how to overcome this using Zerene Stacker.

1. First, convert your RAW file to either a jpeg or TIFF file (16-bit is recommended). I make a new folder called ‘stacks’ where I export them.        
2. Open Zerene Stacker then drag & drop the files into the input window. Be aware that you will have extra files that will be completely out of focus as the autofocus on DSLR’s will go beyond infinity resulting in an out of focus image. Just delete these files.

3. Go to the top menu and under Stack choose Align & Stack All (Both). When this is done, you will see an image in both windows, the one on the left is the individual file and the one on the right is all of the combined files.
4. Set the contrast threshold. This separates significant detail from irrelevant noise or artifacts.

5. Edit>start retouching. View the image at 50% or 100% by setting it in the lower left window. You can alter the brush size by using the brackets ([ ]) on your keyboard. Start at the bottom part of the photo and work methodically through to the top of the image. Click on the sharply focused file from the input panel where you are working in the photo. Where the wind has blown the flowers creating multiple flowers, simply brush over the area painting in the single sharp flowers. Where people and sheep have moved between images, brushing over creates a single, sharp subject. Continue through the image selecting the appropriate sharp image file. When you have finished, go to Edit>commit retouching.

6. Go to File>save output image. I recommend saving as a 16-bit TIFF file. Now you can import the final image back into Lightroom or where ever to finish any necessary retouching and post processing.

Now I’m not saying that you need to do this with every scene to get sharp images, just when you need to go beyond the capabilities of your equipment, but it does open up all sorts of creative possibilities.