Stacking Images For Extended Depth Of Field

Getting this shot with all three flowers in focus isn’t possible in one exposure.

This is a single image shot at ƒ/16. Notice how only the top flower is in focus.

In close-up photography we’re dealing with shallow depth-of-field, even at small apertures. There’s nothing we can do about it in the field—physics is against us. Small camera-to-subject distances always result in one narrow plane of focus. However, it’s possible with software and good shooting techniques to combine multiple images focused at different points and create an image with extended depth offield. In the above flower image, I combined seven different images using the Auto Blend feature in Photoshop CS4 to create one image with all three flowers in focus.

The technique is fairly simple by following these steps:

1) Put your camera on a tripod, compose your image, and determine the proper exposure (shoot in manual exposure mode).

2) Take anywhere from four to 10 exposures, slightly changing your focus point for each exposure. I usually start with the front of my image in focus and move into the scene with each exposure, but Photoshop doesn’t care how you do it. Eliminating movement of the subject is key, so on windy days this technique might be close to impossible to pull off. Also, be sure to use the same exposure and white-balance settings for each image.

3) Download your images to your MAC/PC and open Photoshop. You can use RAW, JPEG, or TIFF images—they all work. Bring your images into Photoshop by using the FILE– Scripts– Load Files into Stack command. Be sure to check the box for “Attempt to Automatically Align Source Images”

4) Go to your layers palette. You will notice each image is on its own layer. Highlight all the layers (click on the top layer, then shift-click on the bottom layer.)

Image focused on the lighthouse.

5) Go to Edit–Auto Blend Images…Check off “Stack Images” and “Seamless Tones and Colors.” Photoshop will now magically create layer masks on each layer to reveal an image that is in focus from front to back. It’s not always perfect, so you may need to flatten the layers and use the clone stamp to fix any oddities.

Image focused on the nearby rocks.

This technique works for any type of image, not justclose-ups. In the series of lighthouse images, I was shooting at a 100mm focal length at ƒ/16. Though I could get reasonable depth-of-field by focusing 1/3 of the way into the scene, I really wanted to create an image that was sharp, front to back, so I took six different exposures focused at different points and combined them. In this case, Photoshop wasn’t up to the task, creating miscellaneous soft spots throughout the scene. I could have fixed it by manually tweaking the layer masks, but instead I ran the images through a program called Helicon Focus (http://www.heliconsoft). I highly recommend this program if you decide to make this technique a regular part of your workflow.

Six exposures combined in Helicon Focus -sharp front to back.

I’ll be teaching these techniques and other fun stuff at my Outdoor Photography Workflow Workout on May 1st and 2nd. Details at jerryandmarcymonkman.com