Focus Stacking in Photoshop
One of the greatest challenges in Macro photography is getting the right DOF (depth of field). Generally, the closer to your object you get, the shallower the DOF becomes. Smaller apertures will let you gain more DOF, but will also block more light, taking into consideration the fact that most handheld macro work is already done with fast shutter to reduce camera shake. If you want to achieve ultra sharp images, with a reasonable aperture, then focus stacking is ideal to achieve that. There’s a lot of equally good software available for focus stacking on the market, but I have decided to demonstrate how Photoshop CS5 copes with it.
As I said before, in order to gain greater depth of field in Macro photography, you will need to shoot with small apertures. This, combined with a fast shutter speed, requires an external source of light such as a speedlight. However, even extremely small apertures do not always guarantee a sharp image with a reasonable depth of field. That’s why focus stacking is ideal to overcome these limitations. First of all, you may shoot with larger apertures and don’t have to use a tripod. As long as the images are composed in a similar way, Photoshop will manage to stack them. However, due to the fact that autofocus is often useless in 1:1 (magnification level) Macro photography, you will need to focus manually. Basically, what you need to do is to ‘scan’ your subject focusing on its different parts. First, focus on one part of your object and release the shutter. Then, moving closer to your object, focus on another part and take the second picture. Repeat these steps until you have covered the area you want to be sharp in the final image. Just look at the pictures below the bottom image was stacked from, and notice how I ‘scanned’ the object. Secondly, the pictures were shot handheld and even though the composition differs slightly, Photoshop still managed to stack them.
After taking the pictures, open all of them in Photoshop and make sure that they are not separate pictures but layers stacked on top of each other. You can either move them manually or use Adobe Bridge. Then, select all the layers.
Next, go to ‘Edit’ and select ‘Auto-Align Layers’. This is especially important if you have taken the pictures handheld and the composition varies slightly. Photoshop will then align all the layers.
Finally, click on ‘Auto-Blend Layers’ and a separate window will appear. Just select ‘Stack Images’ and depending on the processing power of your computer you can take a short break.
Remember, depending on the variation in composition between the pictures, you will have to slightly crop the image.
Thanks for reading and good luck with your photography.
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