Photoshop: Photo stacking for continuously sharp images
The term ‘focus stacking’ describes an image processing technique in which several images of the same motif merge with each other. Differently selected focus points enable a sharp representation over large parts of the picture, which would normally not be possible.
We will show you what you should consider for the correct preparation and execution and how the subsequent image processing succeeds.
Preparation – photography
Good preparation is indispensable and increases the quality of the results that can be achieved in image processing. Focus stacking requires as many identical image series as possible. The only exception is the differently selected focus.
That is why the DSLR camera should always be mounted on a tripod. It is also recommended to use a remote shutter release so that the camera does not have to be touched more often than absolutely necessary. In order to be able to edit the images well later, you should photograph in the file format RAW.
In poor lighting conditions and the resulting long exposure times, even the slightest shocks can lead to blurred images. To avoid this, activate mirror lock up in the camera settings. The mirror will now fold up a short time before shooting and will no longer cause any shocks.
Another factor that should not be underestimated is the lighting on site. Fluctuating lighting has a negative effect on the series of pictures and makes it more difficult to merge them afterwards. Therefore, make sure that the lighting is as consistent as possible, regardless of whether you are taking pictures outdoors or indoors.
Furthermore, you should select a suitable motif for your photo shoot. The general opinion is that the technique of focus stacking is particularly suitable for macro photography. Without post-processing, the often very detailed motifs, such as small animals or flowers, can usually not be reproduced in full focus.
However, even in landscape photography, entire image areas can shine in new splendour thanks to focus stacking. Choose your subject keeping in mind that it must remain motionless for the duration of the shot. Some photographers use specially prepared insects in macro photography.
Tips for a successful execution
Practice makes perfect
For the best possible result, take plenty of pictures with different focus ranges. It is important to focus as evenly as possible. So feel your way forward slowly. In principle, there are two ways of taking pictures.
- Automatic focusing
- Manual focusing
If you want to take pictures using autofocus, you should use the Live View function of the camera if possible. This allows you to see the composition of the image on the display and to move the focus point easily.
Alternatively, you can do the focusing yourself. To do this, simply switch from autofocus to manual focus on the lens. The focused area can be shifted with the focus ring of the lens.
Regardless of which method of focusing you choose, be careful when handling the camera. Any touch, however small, could cause your camera’s viewing angle to change, resulting in different shots. Therefore, make sure that the tripod is stable and the camera is firmly locked in place. Focus on the point closest to the subject and slowly work your way back over several focusing planes.
Post-processing and merging with focus stacking software
Once the entire subject has been photographed, the computer can make changes to exposure, contrast, and similar parameters if necessary. Image editing can be done with most common photo editing software. However, it is important that each image receives the same correction and that there are no differences between them.
Image editing with Lightroom
In Lightroom, value corrections can first be made for one image and then applied to the other photos in the series. To do this, make the desired changes to any image. Then select all images and press Sync. A dialog window opens, which you confirm with OK.
Adjust exposure, contrast and colour values and transfer to all images (“synchronize”)
If you are satisfied with the result of the image processing, open all images in Photoshop or an image processing software with similar functionality. As a free alternative to Photoshop, we recommend the focus stacking program CombineZp, with which individual images can be automatically merged together.
Stacking in Photoshop
Next, select all layers and press Edit – Auto-Blend Layers.
For further processing, all images must now be superimposed as layers.
Insert individual images as layers into a document
Select images and edit – Auto-Blend Layers
Then an additional window opens with the title Automatically blend layers. Here you select the option Stack images and confirm your selection with OK.
Joining the layers may take some time, depending on the performance of your computer. Photoshop analyses the existing layers for similarities and compares them with each other. The focused areas of the individual layers are then highlighted and connected. At the end of the process you have a photo motif which is focused over the entire area.
Bottom line
Focus stacking offers the possibility to combine several differently focused photos into a single sharp image. This procedure is particularly popular in macro photography, where it is sometimes impossible to focus on all desired areas of the subject despite a small aperture and high depth of field. However, focus stacking can also be used for other things, such as landscape photography. The decisive success factors are, as so often, the right preparation and a lot of patience. With the help of the most modern image processing software, image series can ultimately be combined to form one perfectly sharp image in just a few simple steps.
