Although solar eclipses are easily photographed, it's nearly impossible to capture details in both the inner and outer corona in any single exposure. The corona's range in brightness is just too large for the dynamic range of today's photographic emulsions. I have long envied the wonderful composite photographs by people like Wendy Carlos, who labor many hours in the darkroom to produce a composite image of the corona from six or more negatives taken with a range of exposures.
In recent years, eclipse photographers have begun processing their images using the personal computer and image editing programs like Adobe Photoshop. Wendy Carlos used my own negatives of the 1995 total solar eclipse to make just such a composite and the results were published in the August 1996 issue of Sky & Telescope (page 48) (image available via GSFC/SDAC). More recently, an article by Gerald L. Pellett in Sky & Telescope (January 1998, page 117-120) as well as work done by Benjamin Gomes-Casseres has inspired me to delve into this arena as well. Jerry Lodriguss has also produced some nice work.
Below is one of my first efforts in eclipse photography composite imaging. The original images were made by me from Dundlod, India during the total solar eclipse of 1995 October 24. A Sigma 400mm f/5.6 APO telephoto and a Sigma 2X teleconverter were used with a Nikon FE w/MD-12 motor drive. The exposures were made on Kodak Royal Gold 100 at 2, 1, 1/2, 1/4, 1/8, and 1/15 and 1/125 seconds. I scanned the negatives using a Minolta QuickScan 35.
The first image (below) is a staight scan of the 2 second exposure. Although some detail is visible in the streamers and polar brushes, it is very washed out and the inner corona is totally overexposed.
The second image (below) is a composite of "difference" images from all seven negatives. Each "difference" image was created using the radial blur filter (in Photoshop) and subtracting it from the original negative using an offset of 128 in brightness (as described in Pellett's article). A great deal of coronal structure is now revealed although the image no longer looks anything like the naked eye view.
When the above two images are multiplied by each other in Photoshop, the resulting image shows much of the detail hidden in the original negatives (below). I also adjusted the brightness, contrast and color balance of the final image to more closely approximate what the human eye sees during totality. I also superimposed the Moon's disk from one of the shorter exposures, purely for aesthetics.
The final version (below) is a higher contrast version which exagerates coronal detail at the expense of one's visual impression of totality. These are just two examples of many possiblies.
Much experimenting is possible with these techniques and the above example simply gives you a starting point. Russell Brown has prepared an excellent tutorial on Digital Eclipse Techniques using some of my 1995 eclipse negatives and Adobe Photoshop.
Japanese eclipse photographer Shigemi Numazawa has also posted some lovely eclipse composite photos and descriptions of his Corona Digital Techniques.
I'm very excited by this technique and have applied it to my photographs of the most recent total solar eclipses:
I've also begun applying these digital compositing techniques to some of my older eclipse images. I will add more of these processed photos to my Eclipse Gallery pages as I work through my archives:
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Last revised: 2007 Dec 24