Ask Tim Grey eNewsletter
February 12, 2014


 Providing Answers to Photographers for Over a Dozen Years...
 
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Today's Question: Could you please outline how one would approach the blending process for focus stacking using Photoshop?
Tim's Answer: This is a follow-up question related to a prior question regarding the use of focus stacking to expand depth of field. Focus stacking is especially helpful for macro photography, where it can be tremendously difficult (or at times impossible) to achieve the amount of depth of field you’d like to have.

In my previous answer I recommended the use of Helicon Focus from HeliconSoft (http://www.heliconsoft.com) as a great tool for blending exposures. However, you can indeed blend multiple images in Photoshop as well.

The first step is to assemble your multiple captures (each captured at a slightly different focal distance) into a single multi-layered document in Photoshop. You can do that very easily in Adobe Bridge by selecting the multiple images, and then choosing Tools > Photoshop > Load Files into Photoshop Layers from the menu. If you’re using Lightroom to manage your photos you can select the images to assemble and then choose Photo > Edit In > Open as Layers in Photoshop from the menu.

Next, select all of the image layers on the Layers panel by clicking on the thumbnail for the top-most layer, then holding the Shift key and clicking on the thumbnail for the bottom-most layer. Then choose Edit > Auto-Align Layers from the menu, so Photoshop will process all of the images and adjust their alignment based on the content of each photo. This is an important step even if you captured the sequence of images on a tripod, helping to ensure optimal alignment of all details within the series of photos. If you assemble a set of images twice, once with and once without this alignment step, your initial reaction may be that the result without alignment is better. But I can almost guarantee that without the alignment step your result will include more than a few problematic artifacts throughout the image. So, I consider the alignment step mandatory.

Finally, select Edit > Auto-Blend Layers from the menu. In the Auto-Blend Images dialog, choose the Stack Images option, and turn on the Seamless Tones and Colors checkbox, then click OK. Photoshop will then blend all of the layers together into a seamless result. At this point you’ll almost certainly need to crop the image to remove artifacts or areas where all images didn’t overlap.

Under ideal circumstances, the result will be an image that reflects an optimal expansion of depth of field without any visible artifacts. Unfortunately, in my experience the results are a bit mixed. So, again, I find that products such as Helicon Focus provide a better solution in most cases, but if you already have Photoshop it is worth trying out the blending feature for focus stacking before spending money on additional software.
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