August 17, 2017

Practicing Photography for the Solar Eclipse

You've no doubt realized by now that a total solar eclipse will dash across the continental United States next Monday, August 21, 2017.  If you plan to photograph the show, you should already have your solar filter for your camera and a pair of solar glasses for viewing the eclipse directly. Now is a perfect time to test your equipment and accessories to be sure you know where to point your lens and what settings to use before the excitement begins.

First Test Exposure of the Sun
2 seconds, f/11, ISO 100

Evaluative metering
168mm equivalent focal length

Check NASA's web site for when you can see the eclipse. Where I live in western Montana, the sun will be about 92% eclipsed. The eclipse begins at 10:15am with the maximum effect at 11:31am and ends by 12:52pm MT.

Best Test Exposure of the Sun
1/25 second, f/11, ISO 100

Spot metering
448mm equivalent focal length

I took my equipment out to a local park where I have a clear view of the eastern sky and tested for exposure and framing at the time when the eclipse will occur. Here's some of the things I discovered.

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  1. Use whatever is your longest lens for the largest image of the sun and eclipse. A 70-200mm lens at 200mm with a 1.4x teleconverter on my Canon 7D with a 1.6x crop factor sensor gives me an effective focal length of 448mm.
  2. The solar filter makes it difficult for auto focus to work. Before attaching the filter, point your lens at the distant horizon and auto focus there. This sets your lens to infinity focus, which is what you need to ensure sharp focus of the sun. Then switch to manual focus to prevent the camera from trying to focus again when you start taking photos.
  3. It's hard to find the sun in the viewfinder when you have the solar filter in place at maximum zoom. So start with a wider angle of view to locate the star and then zoom in.
  4. Since the majority of the frame is black due to the filter, overall metering (Evaluative or Matrix) provides too bright an exposure. So switch to Spot metering (or Partial metering) to measure the light just from the sun in the center of the frame.
  5. Set the camera to the lowest ISO (100 or 200) and the lens to its sharpest aperture (usually f/8 or f/11).
  6. After a couple of tests, I settled on an exposure of 1/25 second at f/11 and ISO 100. Because I will not see the total eclipse, these settings should work for the entire event. So I dialed them in using Manual exposure mode so they will not change.
  7. If you have a wired or wireless remote shutter release, you will want to attach it so you can take photos without having to look through the viewfinder or at the Live View screen. If you don't have a remote release, set the self-timer to a 2 second delay.
  8. If you have an intervalometer, you may want to set it up to take pictures at regular intervals so you can watch the event more easily. I plan to set mine to make an exposure every minute or two. Later I can combine these into a time lapse or a composite showing the progression of the eclipse.
  9. You will need to adjust the framing periodically as the sun continues to rise in the sky throughout the eclipse.
  10. For those in the western US who are experiencing smoke from wildfires, I have good news: the smoke had no effect on my exposures or the visibility of the sun. As the sun rises higher in the sky, it is above most of the haze, helping to ensure a clear view.
Finally, be sure you have a fully charged battery and spare along with plenty of empty memory cards. You might also want to take along a chair, a hat, some sunscreen and bug spray as well as water and snacks. The entire eclipse process lasts about 3 hours, so be prepared for the spectacle!