Wednesday, March 19, 2014

Focus Stacking for Macro and Close-Up Photography

Focus can be a difficult prospect with macro and close-up photography. The closer you are to your subject, the thinner your depth of field (the area of your subject in focus) becomes. Even if you use a narrow aperture (like f/22, read more here), your widest depth of field might be less than an inch, front-to-back. Focus stacking is a technique for shooting and combining a series of photographs to achieve focus across as much of your subject as you want.

Focus Stacking for Close-Up Flower Photograph | Boost Your Photography
Close-up flower, photographed using 50 mm lens and 10x close-up lens. 3 images focus stacked.

How to Photograph a Series for Focus Stacking

In order to easily blend your series of images, you will want to shoot in Manual mode (M) on your camera. This will ensure that all your photographs have the same settings and exposure. (Unsure about manual mode? Take a test image of your subject first, using whatever mode you are comfortable with ... Av/A for aperture, Tv/S for shutter, P for Program, or even just Auto. Then, look at the settings your camera chose for that picture. Switch into manual mode and dial in those same settings for ISO, aperture, and shutter speed. Ta da!)

You will also want to use manual focusing. You can either decide on your composition and twirl the focus ring on your camera lens until your subject looks perfectly in focus, or you can twirl the focus ring on your camera lens first and then move your body slightly forward or backward towards your subject until it looks perfectly in focus. (The first method will give you exactly the composition you want, while the second method will give you the closest-in focus you can get.)

Then, think about your composition and exactly which parts of your subject you do or do not want in focus in the final image. Maybe you want every single thing in focus, or maybe you only want one certain area of your subject to be in focus.

Focus Stacking for Flower Photography | Boost Your Photography
2-image focus stack of a close-up flower

For this photograph of a flower I knew that I wanted the center of the flower to be in focus, but I still wanted the petals blurred and out of focus. When I took my test shot, I focused on the front of the flower's center, and I was able to get about half of the center in focus. I then took a second shot keeping the back half of the flower's center in focus. You can see that the rest of the petals are not in focus while most of the center (except for the very foreground) is in focus.

Since you are using manual focus, the movement required between each shot will be very, very small. All you need is the slightest of leans closer or farther from your subject. Practice looking through your viewfinder (or using Live View, if you prefer) and watching the area of focus move through your subject as you lean in-and-out slowly and slightly. When you are ready to photograph your series for focus stacking, start from either the closest in or farthest out that you want in focus. Take the first photograph, move slightly to adjust the focus, freeze and take the next photograph, and repeat.

Focus Stacking and Processing

Once you have your series of photographs with varying areas in focus, you are ready for the post-processing focus stacking step. These directions and 'how to' images are using Adobe Photoshop. There may be other options available for focus stacking, but this is what I use.

The first step is to open each of the individual images in Photoshop. Then you will copy and paste them all into one single file. Hold down shift and click to select each of the individual layers. Then choose Edit -> Auto-Align Layers. I find the Auto projection usually works just fine. Click OK. This will exactly line up all of the individual images. Since you have to move slightly to take each picture and change the focus, the images will each be slightly off from each other, and this will correct those differences.

After the Auto-Aligning is finished, all of your layers should still be selected. Then choose Edit -> Auto-Blend Layers and choose the Stack option. Click OK. Photoshop will then select the sections from each image that are best in focus and create a composite final image.

Focus Stacking Combines In-Focus Sections from a Series of Photographs | Boost Your Photography
Click caption to see focus stacked image larger on Flickr.

This series shows the results of focus stacking three individual photographs of frozen droplets. The top three images show the different pieces of the three images that were selected for inclusion in the final, blended, focus stack image beneath. (You can tell from the final image that I really needed a fourth photograph, of the ice crystals closest to the camera, in order to get them in focus as well.)

Click caption to see the final image larger on Flickr.

This collage shows a comparison of the four individual photographs and the final, focus stacked image. You can see, again, that small sections of the leaf are still not in focus, because the area in focus jumped slightly too much from image to image (for example, look at the middle of the near-middle leaf). The key with focus stacking is always to move very slightly and try to overlap the regions in focus from image to image.

Try Focus Stacking

Focus stacking is a great technique to try when photographing a close-up or macro subject when you want a larger area of the photograph in focus. Focus stacking allows you to combine multiple images with slightly different areas in focus into one, well-focused final image. The tricks for successful focus stacking and blending are to use manual settings and focus and to make only minimal movements from image-to-image in order to ensure perfect focus.

Focus Stacked Photograph of a Close-Up Flower | Boost Your Photography

What will you use focus stacking for? Share an idea or photograph in the comments below.

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