Focusstacking

Combining images with different focus settings is a way to achieve a greater depth of field

There are times when depth of field alone might not be enough to keep the scene in front of you in focus. It might be that you are shooting a macro image, where depth of field is always very shallow, or you have something in the foreground and want to use a medium aperture for a better quality image.

Focus stacking is a technique where you take a number of images, each with a slightly different focus setting, and then combine them into one super-sharp image with ultimate depth of field. Place the camera on a tripod, compose your image, switch to manual focus and then adjust the focus so that the nearest object is sharp, and then manually change the focus setting until you have covered the entire distance, taking a photograph each time.

To assemble the shots, first process the shots with the same settings in Lightroom, then, with them all selected, use the Open as Layers in Photoshop command. In Photoshop, select all the layers, then select Edit>auto Align Layers... While the images should line up perfectly as they were shot on a tripod, the lens might ‘breathe’ slightly as the focus is changed, causing the image to change a little between shots. Finally select Edit>auto Blend Layers... and click Stack Images. Make sure that Seamless Tones and Colors is selected.

Obviously if your subject moves at all between exposures, the process won’t work, but for many subjects, this is a way of achieving a broader depth of field than any single image can achieve.

Certain Nikon cameras, including the D850 and the Z 6 and higher, have a built-in focus stacking function, known as Focus Shift Shooting. This allows you to focus the camera on the nearest point, and then automatically take a series of pictures where the camera changes the focus slightly each time. You can set the number of shots to 100 (the camera will stop when the lens reaches infinity anyway), or a specific number of images.

The main setting that you will need to experiment with is the Focus Step Width. Too low a number and you will be taking unnecessary images; too high and the focus shift can be greater than the depth of field in each individual shot, leading to out-of-focus bands in the assembled shot. For shots with an inherently shallow depth of field, use a lower number; for individual shots that will have a great depth of field, use a higher number.

For many subjects, focus stacking is a way of achieving a broader depth of field than any single image can achieve

Top: Bridge over the River Dart, Dartmoor. The depth of field just wasn’t quite enough on this image, so I used the Nikon Focus Shift on the D850 to take three images at different focus settings (inset images). The result was stacked in Adobe Photoshop for exceptional depth of field.