Digital SLR Photography

Build your focus stack

By Caroline Schmidt. Posted

You’ve taken your tripod-mounted frames that perfectly overlap as you step down the focus through the scene. You may have also taken multiple exposures for each of these frames and are now wondering what to do with them all. Thankfully, as long as you’ve used a tripod and taken the images systematically, organising and blending the frames should be straightforward – no matter if you're faced with an ample 12 or overwhelming number of exposures.

Certain cameras and software options offer highly-effective automated functions for exposure blending and focus stacking, which do most of the work for you. Saying this, however, if your aim is for professional-grade quality you may want to consider the more lengthy and detailed process of manually blending your images to ensure an area doesn't get missed, which we detail in Step 4.

As this image of Trebetherick near Rock, Padstow, is shot at sunrise with the sun directly in the frame, we’ll need to blend the exposures before we start the focus stacking. Often stacking all the images at once means Photoshop averages out the exposure and you lose the benefits of bracketing. As these two techniques do need to be applied separately for best results, jump to the section in the tutorial that’s most applicable to you.

_1. Exposure blend _

As the sun is in the frame, four exposures were taken while focused on the farthest point in the scene, which need to be combined first. You can do this in Lightroom before sending the images to Photoshop by clicking Photo>Photo Merge> HDR * or open directly in Photoshop and go to *File>Automate>Merge to HDR Pro. Add your exposures by clicking Browse and the OK.

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_2 Flatten your files _

Once you’ve blended your HDR image, go to File>Save As and flatten the image from a PSD to a JPEG so it can become part of the focus stack. If you’ve done multiple HDR images, one for each frame that you want to later stack, you’ll need to save each HDR image as a JPEG file. Retain the PSD files in case you want to do adjustments to the blends in the future.

3. Align your layers

Go to File>Scripts> Load Files into Stack. Select your files and check Attempt to Automatically Align Layers and click OK. If the option to align isn’t available in your version, you'll need to align the layers by selecting each layer in the Layers palette while holding Shift key and choose Edit>Auto-Align Layers. Leave Auto selected and click OK. Now choose either Step 4 or 5.

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_4. Automatic stacking _

To let Photoshop’s automatic blending do the work, go to Edit>Auto-Blend Layers and select Stack Images and click OK. We suggest you turn off Content Aware Fill Transparent Areas if you’ve shot the images correctly as you shouldn't need it. Once it’s complete you can apply any final crops, tonal, colour and sharpening tweaks to your image and save as a JPEG.

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_5. Manual stacking _

For those who don’t like to leave anything to chance, you may prefer to manually blend your images. When you have all your images aligned in the Layers palette (as per Step 3), add Layer Masks to all the layers (Layer>Layer Mask>Hide All). Using the * Brush Tool* set to White, meticulously brush over the sharpest areas in the scene as you work your way back through the image.

edit final - helen dixon

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