This spring was a spectacular year for the lady slippers in my back yard. There was one cluster of 20 flowers, with smaller plants of one to three flowers nearby. The flowers are located on the edge of the forest, next to a pile of cut logs with a rack of firewood behind it. Natural lighting can be difficult to deal with as the sun is low on the horizon sending shafts of light through the foliage of the trees. Occasionally overcast skies provided flat light that reduces or eliminates harsh shadows on the flowers. It was an opportunity to try several techniques capturing these beautiful flowers, and I went out early each morning while the air was cool and still. Once the sun starts warming the ground, air currents are created and even the slightest breeze results in significant movement in these large flowers on long stems. I often used a 160 LED lamp to illuminate a single flower. Most images are captured with a Sigma 150mm lens on a Canon 5D Mark II. I used tripod or beanbag for support and a wireless remote shutter release to avoid any movement during exposure. In addition to single captures of the scene, I made many captures with focus stacking in mind as well sets of images (a series of the same image at all f-stops) for use in teaching programs. I also made a few images using a 50mm f/1.8 on the Canon 7D.
The first set of images were made by selectively focusing on different parts of the flower, then merging them into one image file using Helicon Focus stacking software. Last year I had done quite a lot of image taking and analysis in an attempt to understand where focus stacking works and where it doesn’t. The extensive blog posts totaled 30 pages. Helicon Focus recently had an update and added a new stacking algorithm which I used on a trial basis. I was satisfied that it performed well on these image and purchased a one-year license ($30) for the Helicon Focus Lite. I plan to reprocess the images sets I took last year to see if the new algorithm solve some of the problems I described in my posts last year.
The reason for using a stacking program is to benefit from an extended depth of field at the subject while shooting at a large aperture to retain the soft out-of-focus (OOF) background. The images are labeled as a single exposure or number of images stacked, and the f-stop used.
To better see the effect of apertre on depth of field, images of a scene were captured at a various f-stops, and one image was constructed of several captures stacked together. The higher the f-stop (smaller aperture), the greater the definition in the background structure. As the aperture is opened, the depth of field lessens and the background becomes a pleasant, soft blur. Unfortunately, the wide aperture doesn’t capture much of the flower in sharp detail, which is where focus stacking can be of benefit. Care must be taken in capturing images for focus stacking to ensure sufficient overlap in the regions of sharpness. The technique doesn’t always work cleanly, and in some cases there are artifacts that require a lot of editing to correct, if they can be corrected at all.
