How to focus stack a set of images in Photoshop

I recently rented a Nikon 105mm VR Macro lens for a weekend, and wanted to experiment with different types of macro photography.

One of the things I was most interested in was focus stacking. See, there's a problem with macro photography in that you're dealing with a depth of field measured in millimeters when reproducing images at a 1:1 ratio, even stopped down to f/8 or f/11. And, wanting to avoid diffraction at higher apertures, there's no way to take a straight-out-of-camera picture of a 3D object that's sharp from front to back.

(There's also a video version of this post, embedded below)

Fixing the blurry focus on some Raspberry Pi Camera v2 models

The original Raspberry Pi Camera model v1.3 came from the factory set to ∞ (infinity) focus, so when you used it out of the box for something like a landscape timelapse rig, or for security or monitoring purposes (where the Pi is at least 5 meters away from the subjects it's recording), everything would look crisp and sharp.

For many fixed-focus cameras and lower-end camera sensors, it makes sense to set them to infinity focus; closer objects are still recognizable, but slightly blurry. Most of these cameras don't need to focus on a person a meter away for a portrait, and they're also rarely used for FaceTime-like video chat.