Macro Flower Photography: A Tutorial in Focus Stacking

Editor’s note: This excerpt first appeared in photographer and author Harold Davis’ recent Focal Press book, Photographing Flowers: Exploring Macro Photography with Harold Davis.
The closer you get in macro flower photography, the fussier focus gets. Since “fussy” is not a technical term, let me explain. Because focus is inherently shallower as you get closer to your subject, slight variations of distance between camera and subject throw you out of focus very quickly, and even fully-stopped down you may not have enough depth-of-field for your entire photo to be in focus.
Certainly, stopping your lens down to its smallest aperture, observing whether you have the in-focus areas you want, and seeing if there is any way to position the camera to improve the amount that is in-focus is a good way to start. But bear in mind that stopping down a lens comes with some downsides: optically your lens may not perform best at its smallest aperture, and when the aperture is small you can’t use a shutter speed fast enough to stop motion.
An approach that often can surmount these obstacles is to use focus stacking: shooting at a number of different focal points and combining the images in Photoshop to create a hyper-focal image that has an extended area that is in focus.
The combination of images can be accomplished by hand-painting to select the areas you want or using automated layer alignment and stacking software (see text box below). Whichever method you choose, bear in mind that the more focal points you shoot, and the more images with differing focal points you bring to the party, the more successful your stacking is likely to be.

In my garden, I found a perfect poppy core that had formed after the poppy’s petals had fallen off. Quickly, before the breeze could blow the construction apart, I gently cut off its stem, and brought it inside to my studio with the idea of photographing the core close-up.

I didn’t dare put the poppy core down on a table because it would have immediately fallen apart. So, one-handed, I found a paper clip and bent it to make a small “stand.” I pushed the stem of the poppy onto the open end of the paper clip – and it fit perfectly. Then, I placed the poppy and its improvised stand upright on a black card underneath a light tent.
Photo: 85mm macro, 20 seconds at f/64 and ISO 100, tripod mounted

With the poppy core mounted on a paper clip, I decided to shoot an image showing the entire core in focus. It was clear that I would have difficulty achieving this goal in a single shot, so instead I made three captures: one focused on the front (top), one on the middle (center), and one on the back (bottom).

I made three shots focusing on different areas of the poppy core: first I focused on the front (top); next I focused on the middle (center); and then I focused on the back (bottom). I combined the three shots together in a layer stack in Photoshop and used layer masks to “paint in” the areas in each capture that were in focus. This combined version (below) is much more in focus overall than any of the individual captures.
Photos: 200mm macro, 3 exposures each at a different focal point combined in Photoshop, each exposure an 1/8 of a second duration at f/4.5 and ISO 100, tripod mounted

Layers Palette

I placed the three shots together in the Layers palette in Photoshop in a layer stack (right – INSERT IMAGE: “Pg158-04-poppy layer palette”). I then used layer masks to paint in the areas in each photo that were in focus. When I combined the three layers by merging the stack down (below), I had — voilà! — a single photo with an extended range of focus.

How to do it in Photoshop: Automated Focus Stacking
Here’s how to create an image with extended focus using automatic focus stacking:

1. With the camera on a tripod so it doesn’t move, shoot a number of frames using the same aperture setting but with different parts of the image in focus. Try to make sure that everything you want to be in focus is in at least one shot.
2. Process the images in Lightroom or Adobe Camera RAW (ACR) using the same settings for each one, and load the photos shot at different focal points into Photoshop as a single layered document.
3. In Photoshop, in the Layers Palette, select all the layers and choose Edit > Auto > Align layers to make sure all the layers are in alignment (even a tiny amount of movement on the tripod could ruin the focus stack).
4. In the Auto-Align dialog, make sure to choose Auto as the projection method.
5. To blend the images with different points of focus, choose Edit > Auto-Blend Layers.
6. In the Auto-Blend Layers dialog, choose Stack Images as the Blend Method.
7. Auto-Blend creates a mask for each stacked layer so that only the portions of the image that are in focus are visible. To continue working on your focus-stacked image, you can choose Layer > Flatten image to merge the layers down into one photo.
8. You may need to crop your image slightly before continuing to compensate for any size adjustments created by the Auto-Blend feature. Also, you may have to retouch some areas of the image that didn’t align exactly right using the Clone Tool.

Harold Davis is an award-winning professional photographer whose work has been widely published and collected. He is the author of many best-selling books about photography, Photoshop, and digital art, including The Photoshop Darkroom series and Photographing Flowers: Exploring Macro Worlds with Harold Davis from Focal Press. Harold’s photography blog, www.digitalfieldguide.com/blog, is read by more than 25,000 visitors each month. His latest book from Focal Press is Photographing Flowers: Exploring Macro Worlds with Harold Davis ($29.95). His next book, Photographing Waterdrops: Exploring Macro Worlds with Harold Davis ($29.95), is currently available for pre-order and will be available in June 2012.