Of course notâ€”thereâ€™s one more technique to try: focus stacking. While the technique may be tricky to master, it will help get that shot sharp, even if you canâ€™t get that aperture narrow enough. So, what is focus stacking? How do you use focus stacking in photography? Hereâ€™s what you need to know about the focus stacking technique.
What is Focus Stacking?
Focus stacking is similar to High Dynamic Range (HDR) photography, because it solves a problem by merging several photos together. While HDR merges photos taken at several different exposures together, focus stacking merges images taken either with different focal points, or sometimes with different aperture values. The photos are then stacked together using Photoshop or a specialized focus stacking software in a way that allows more of the shot to appear sharp.
Say you are taking a landscape photo, but there is an element in the foreground. You want both the landscape and that foreground element to be sharp, but since thereâ€™s some distance between the two, you can only get one or the other sharp, even with a wide aperture. However, if you take one photo focusing on that foreground object, and another photo focusing on that background, you can easily layer them together in Photoshop, then replace the out of focus background in the first photo and replace it with the sharp background in the second photo. Thatâ€™s focus stacking.
Focus stacking can involve more than one image. If you want to print the image in a larger format, youâ€™ll need more layers. If you are close to the subject like in macro photography, youâ€™ll need more layers. A few layers can be easily merged together in Photoshop, but images that involve several layers are best merged with a specialized software, such as TuFuse, Helicon Focus or CombineZM.
How To Use Focus Stacking
1. Decide on the Number of Images Youâ€™ll Take
Before you get started, how many photos will you need? A basic background replacement like the example above can involve just two layers. If you need to use a wide aperture because of the available light, youâ€™ll need more images. The sharper you want the shot to be, the more photos youâ€™ll want to take.
2. Set Up a Tripod
To make layering the images together easier, set up a tripod so your camera doesnâ€™t move at all between shots.
3. Take Several Photos, Moving the Focus Point in Each Shot
The best way to do this is to use single point autofocus, and move the point each time. The most important part to get right is that the focal points are close enough together. You donâ€™t want to have a focused portion then an out of focus portion and then a focused portionâ€”you need the points to be close enough together that the entire object is sharp. If the points are spaced too far apart, youâ€™ll wind up with a focus that waves in and out. With a narrow aperture, the points can be a bit further apart. Thatâ€™s why you need more photos if you have a deep depth of field. If in doubt, take more photos than you think you need. As you practice the technique, youâ€™ll get the hang of anticipating how many photos you need.
4. Align the Photos
Even with a tripod, your photos wonâ€™t quite line up exactly. Thatâ€™s because adjusting the focus will change the focal length just a bit; in other words, the lens zooms in and out just a bit when you refocus. In Photoshop, you can use the auto align feature once you have copy and pasted the separate photos into one file by heading to Edit > Auto-Align Layers. Or, you can use software specifically designed for edits like focus stacking.
5. Select the Sharpest point in Each Photo
With the layers on top of each other, now youâ€™ll need to select the sharpest portion in each photo to blend (specific focus stacking software will often for this for you). To do this in Photoshop, you will create a layer mask on each separate shot. Remember, the white portion of the layer mask determines what part of that layer shows, so youâ€™ll paint black over the sharpest part of each separate shot.
6. Finalize the Shot
Once youâ€™ve selected the sharpest part of the shot using layer masks, you can merge those layers into one shot. Then, you have a single image that you can edit and use just as you would a single shot. But, since you combined the sharpest part of each image, you have a shot thatâ€™s sharper than a single image by itself.
Alternatively, you can take the same photo at different aperture settings, then combine them into a single photo. While this method doesnâ€™t get a photo thatâ€™s as sharp as adjusting the focus point, the images are easier to merge together, since the focal length doesnâ€™t move between shots like it does when you refocus between shots.
Focus stacking can become quite time consuming, and focus stacking large amounts of photos together requires specialized software. Using this technique is a great way to get a sharp shot when a narrow aperture isnâ€™t enough or just isnâ€™t possible with the available light.