Focus stacking; creating a large depth of fieldsaturday 12 March 2011, 20:03 by Elja Trum | 19080 times read | 1 comment
Depth of field is the part of an image that is in focus. The depth of field can be very large or very shallow. This depends on the lens you use, the aperture you've set, the size of your sensor and your distance to the subject. Most of the time you can get enough depth of field, but if you can't there is a way to combine the depth of field of multiple photos. This is called focus stacking.
The shortage of depth of field is most often experienced in macro photography. Even when you use an aperture of f/16 or f/22 you can end up with a depth of field of just a tenth of an inch. This can make it difficult to get a usable part of your photo in focus.
This flower, shot by Ide Geert Koffeman, is sharp over the whole image.
Obtained by focus stacking seven separate photos.
Focus stacking is literally stacking the in-focus parts of multiple images. You start by taking multiple photos where all settings are equal, even the position of you camera shouldn't change. The only thing that does change in every photo is the point of focus.
In every photo another part of the object you're photographing should be in focus. On your computer you can combine these photos to one photo with a large depth of field than possible to create in one shot.
Getting the shots
Before you can combine the photos you'll have to take them first. To get a good focus stacked image, you'll have to make sure that the differences in each photo are as small as possible. Using a tripod is a must! This helps you to get the same composition on each shot.
When composing you're image, make sure to leave some room on the edges of your photo. You'll lose some of this edge in post-processing, so be sure to frame your subject a bit to wide for your taste. Cropping will be required afterwards.
You'll want your lighting to be the same in all the shots also. So switch to manual to get a constant exposure of the object you're shooting. Set the focus to manual also and start by focusing on the front-end of the object you want to be completely in focus. Now take your first shot.
Rotate the focus ring on your lens slightly to move the focus point a bit further along the object. Make sure that the part to be in focus now is overlapping the in-focus part in your previous photo. You'll need at least three photos for a good focus stacking, but it's okay to take thirty too.
Stacking the focus
If you have Photoshop CS4 or a newer version, you won't be needing any extra software. Focus stacking is one of the things you can do with Photoshop. Start by loading the photos into Photoshop and putting them together in one file. Each photo should have its own layer. The order you'll use is important; each new layer should be the next step in focus depth. If you mix them up stacking them won't work.
When you've got all the photos together in one file, select all layers. You can do this by clicking the top layer in the layer palette, hold down your shift key and click the bottom layer. All layers are marked blue now. Go into the edit menu and choose auto-align layers. In the window that opens, just select ok. The automatic mode should do the trick. This process aligns the layers so any movement in between the different shots is corrected.
Next step is combining the layers into one. Again, choose the edit menu, but this time select auto-blend layers. In the window that appears you choose the blend method Stack Images and also check the Seamless Tones and Colors. Press ok do let Photoshop work its magic.
In most cases the automated result will be good. If you find something to be off, you can correct it by editing the layer mask Photoshop created. You'll need to crop the edges out to get your final photo. In the following video I will explain and show how it's done.
If you don't have Photoshop, there is a free alternative: CombineZP. This program only runs on Windows. Unfortunately Photoshop Elements (the affordable version of Photoshop) does not allow for automatic focus stacking just yet.
Other software for Focus stacking
Besides Photoshop there are other programs to create a focus stacked image.
- CombineZP (free)
- Helicon Focus
- Zerene Stacker
If you haven't tried focus stacking yet, it might be worth trying. It's a great way to get an enormous depth of field in your macro shots! And as you can see here, it's not as hard as it sounds.
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