David Saffir: Blending Macro-Images For Depth-of-Field
Jun 2013 04

One of the most intriguing tools in Photoshop is layer alignment and blending. One practical use for these is macro photography – you can create images that have depth of field that is nearly impossible to get in a single frame.

Why? Because a 105mm macro lens on a full-frame camera has depth of field of about 0.6mm at f/16 – in other words, a very, very thin slice. Combining multiple images with different focal points gives us – voila! … a merged macro image that should be completely in focus, front to back, near to far.

Here’s how it’s done:

Use your camera of choice, preferably with a macro lens. Create a normal setup, with the camera on a tripod. Set up or manage lighting, put the camera on aperture priority, and meter. I typically use mirror-up mode as well, and shoot with a remote. Shoot in RAW format if you can. (I used a Nikon D3 digital camera, and the Nikkor 105mm Macro VR lens).

Typical aperture on these shots ranges from f/8 to f/16 in the 35mm class – higher f/stops tend to soften the image through diffusion error. Start at f/8 or f/11.

I usually work close to the lens’s minimum focusing distance. I shoot several frames of the subject, changing the focal point manually to different parts of the subject, left to right and/or top to bottom. Take care: the camera must remain absolutely unmoving so that the frames will register with one another. If we could mark the focal points for all the images, they might look like this:

Transfer the images to a folder on your computer. Open the folder with Bridge. Select the images you’ve captured (in this case six), press Command-R to open them in Adobe Camera RAW. You’ll see this screen:

Make your adjustments to the first picture only (examples of controls outlined in yellow. Be conservative. Now click “select all” (outlined in blue) in the upper left corner of the dialogue, and then click “synchronize”. All of the RAW files will be updated.

Now click the “Done” button (shown by blue arrow) in the lower right hand corner. Camera RAW will close and return to Adobe Bridge.

The six images will still be highlighted in Bridge. Go up to the main menu, choose Tools>Photoshop>Load Files Into Photoshop Layers.

The images will be loaded into a single Photoshop image with, of course, six layers. Open the layers dialogue and select all the layers.

Once this is completed, go to the main menu, and click Edit>Auto-Align Layers. You’ll see a bigger dialogue, again just click Auto.

Once this is finished, go back to the Edit menu, click Edit>Auto-Blend Layers. Click on Stack Images, and Seamless Tones and Colors. Click OK.

Photoshop will launch into an analysis of all the layers, create layer masks to use the best portions of each layer, and blend the images. You should see an amazingly sharp image with significant depth of field. Here’s an example:

I should add one point here: take more pictures, with more focal points, than you think you need. Once the images are blended, you’ll see the difference.

David Saffir is a commercial and fine art photographer and printmaker, located in Southern California, and a well-known speaker at workshops and conferences across the US.