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Other than for special effect, photographers generally do not want out-of-focus images. But sometimes, regardless of which camera settings are used, not every detail of an image can be captured tack sharp. Depth of field (DOF) can be so shallow, that interesting aspects of the photos are without sharpness. Setting to a smaller aperture may be used to increase DOF, but moving the aperture farther from a lens’s sweet spot introduces lens diffraction into the image, again resulting in some fuzziness. Also, if stopping down the camera’s aperture, shutter speed will need to be increased and blurry images may result. Increasing ISO to help with the exposure will introduce digital noise to the image.
So, how do you shoot with the best aperture and shutter speed combination, and get sharp images from front to back of an image? A technique that can help resolve this problem is called focus stacking. Here’s some helpful info about this technique.
Focus stacking is similar in principle to HDR. However, with focus stacking, images are captured with different focus points, and later combined in Photoshop, to create an image with more DOF than would be possible with a single exposure. Landscape and macro photography are two genres of photography that benefit most from using this procedure. Be warned – calm winds and reasonably stationary objects are a must!
Before beginning to shoot, it is always helpful to know a lens’s sweet spot, defined as the aperture that the lens produces its sharpest image. (It is usually found about two to three stops from wide open.) Experiment until this important setting is determined.
There are two basic scenarios when shooting landscapes, that may benefit from focus stacking. The first is when the subject is a close foreground object, with an interesting background, both desirable aspects to be in sharp focus. The second, is when using a telephoto lens (which typically has a shallow depth of field) and the subject covers multiple distances, that may be brought into sharper focus. (FYI: If shooting a landscape with a wide angle lens, the DOF may be adequate enough to capture a sharp image that has no benefit in being processed by focus stacking.)
Tip: Here is a little trick to find out if focus stacking will benefit an image when photographing a scene or subject. After composing the image, set the focus point about one third into the image. Then, using Live View, enlarge the image and check to see if the foreground and background are sharp or blurry. If either or neither are in focus as sharply as desired, the image could benefit from focus stacking.
Macro photography can benefit from focus stacking more than any other type of photography, because a macro lens has an extremely shallow depth of field.
Tip: As often used when capturing HDR images, take a shot with your hand in front of the camera before and after each series of images. When working with the images later, this will make it easier to tell where each series starts and ends.
Processing the files to accomplish the final image may seem like the most difficult part of creating a focus stacked image, but it’s really very simple to do in Photoshop. Here’s how:
Note: If you are using a Lightroom and Photoshop workflow, after importing your images into Lightroom, instead of following steps 2 through 5, you can simply add all your images into Photoshop layers by selecting all your images, then go to Photo/Edit in/Open as Layer In Photoshop. This will open all the selected images as layers. You will then have to Align your images by selecting all the layers in the layer palette, then go to Edit/Auto Align Layers. Then continue at step 6 above.
It is nearly every photographer’s intention to capture the sharpest images possible, and focus stacking can be another tool to help you achieve this goal. The trick to this whole process is to take enough focused images, to create a final photo that is in focus from foreground to background. The results can be amazing once you get the hang of it! Give it a try and post your results and any questions you have here.
This week on dPS we are featuring articles on special effects. Check out the others that have already been published here: