Thanksgiving Cactus

We have a Thanksgiving Cactus in our sunroom that blooms each year during November. Beverly rooted this particular cactus from a stem of a larger one we had in the sunroom of our old house; that plant was too large for the sunrom in our new house and the original cactus now lives with one of our nieces. There is a snapshot of the original cactus taken exactly five years ago (11/25/2015) in the Additional Images section below.

Thanksgiving Cacti are not the same as Christmas Cacti (or Easter Cacti, for that matter), they are all different species. Thanksgiving Cacti (also called Zygocactus) have serrated or “toothed” leaf segments with 2 to 4 pointy spines on each side while the leaves of the Christmas cactus have a more rounded, scalloped edge. (There are more details and photographs of these three cactus varieties in the link in the Additional Information section below.)

I bought a macro lens for some of the caterpillar photographs last year (please see the post Black Swallowtail Butterfly Caterpillar Diary). Recently I have been identifying other subjects to photograph inside the house, during the winter months, and this winter-flowering cactus was one opportunity.

I wanted to take closeup photos of the new flowers but quickly remembered one of the disadvantages of Macro (closeup) photography: a very shallow depth-of-field for typical setups (I have defined Depth-of-Field on the Definitions page). After some research, I identified a technique which would allow me to create a good image from multiple photographs: focus stacking (which is also defined on the Definitions page). To use this technique, multiple photographs are taken, each one focused at a different point on the subject, and the resulting photographs are combined in Photoshop. The distance between the different points are determined by the depth-of-field for the specific setup which include lens focal length, lens aperture, and the distance between the subject and the camera’s image sensor, plus others. For the featured image, the depth-of-field of a single image is slightly more than 1/2″.

When I attempted to set-up the camera for a different flower on the same plant, I realized that since the flower hung down I had to point the camera upward but there was no room for the tripod. I raised the plant by putting the plant on a small table on the coffee table where the plant is normally located. I wasn’t pleased with the result as the flower probably had been open for several days, but there was a new bud opening which I was able to photograph the next day. That image is the featured photo, which is the combination of five stacked photos. There are snapshots of the setup in the Additional Images section below.

Setup Problems

In my attempt to take these photos, I encountered a number of problems including vibrations from people walking in the house adjacent to the sunroom which resulted in camera and subject motion during long exposures. If you would like additional information about these problems and others and my solutions, please Contact Us.

Additional Information

Thanksgiving Cactus or Christmas Cactus – Farmers’ Almanac

Additional Images

Technical Data

Thanksgiving Cactus Merged

  • Date: 11/24/2020
  • Time: 9:52 AM
  • Camera: Canon EOS 77D
  • Lens: Sigma 105 mm f/2.8 Macro EX DG OS HSM
  • Settings:
    • Lens: f/8
    • ISO: 400
    • Shutter: 1/10 sec
  • Cropped image is 4916 x 3276 px

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