Thursday, August 30, 2007

Lessons Learned: Photographing the Lunar Eclipse

For the August 28 lunar eclipse I decided to go shoot by Mono Lake, where there would be no light pollution and at an elevation of about 7000 feet there would be minimal atmospheric interference. I spent the previous night in Yosemite Valley and travelled to the South Tufa access point at Mono Lake to spend the night of the eclipse. To plan for the eclipse, here are some links that I used.

Lunar Eclipse Photo Examples and Shooting Advice:
http://www.mreclipse.com/LEphoto/LEphoto.html

Aug 28 Lunar Eclipse Phases & Times:
http://sunearth.gsfc.nasa.gov/eclipse/LEmono/TLE2007Aug28/TLE2007Aug28.html

I really liked the example of a wide angle lunar eclipse sequence in a particular setting, so I set up one camera to leave with one wide perspective, and I used another to capture zoomed shots of the moon at various phases of the eclipse.

I did a fair amount of exposure bracketing, but I had some focusing problems during the darker phases of the eclipse. In my case I had added a 2X teleconverter to my lense which forced manual focus, so I assumed that I simply wasn't focusing accurately enough. Examining the shots on my computer the next day, the stars revealed that the real culprit turned out to be the rotation of the earth. My 70-200mm lens doubled via a 2X teleconverter to 400mm is equivalent to 640mm on a 35mm camera, so in the process of magnifiying the detail of the moon I was magnifying the motion of the moon as well. With the moon 10,000 times less bright during the eclipse, about a 15 stop shift darker, and the 2X teleconverter also cutting my lens's widest aperture down 2 stops from f/4 to f/8.0, I could focus on the moon sharply at any given instant, but the exposure times were simply too long as both the moon moved and my position moved (the surface of the earth rotates at over 1000 miles/hour). As I examine the shots in more detail it'll be interesting to see at what exposure time the motion becomes too great at that level of zoom.

Update: Using the "500 Rule" to determine an approximate maximum exposure before the stars and moon start to "drag", divide 500 by the effective focal length of 640 mm and you get 500/640 = 0.78.  So any exposure time under 0.8 seconds or so will produce a photo without that apparent motion blur.

A different issue I've found related to moon shots and image stabilization is that when I bracketed I wanted to use Photomatix HDR software to combine multiple exposures to really bring out the moon's detail. Unfortunately the IS system seemed to re-acquire a new lock on the moon in between shots, which moves each shot slightly and destroys the alignment of the shots relative to each other. Normally HDR software can attempt to restore alignment across multiple shots, but the information in each shot is so different that there doesn't seem to be enough information for the software to use to perform alignment automatically. I guess I'll have to use Photoshop skills to superimpose, align, and blend multiple shots.

My biggest challenge however turned out to be one that I had anticipated: battery power. What I hadn't anticipated was shooting in yosmite all day then catching a nice sunset in the Mammoth Lakes area before heading over to Mono Lake. I started the night with neither of my cameras fully charged, and having to do a little battery shuffling and charging during the night cost me a couple of key shots from the sequence I wanted to complete. Lesson learned.

The still partially eclipsed moon set over the crest of the Sierras near 13,000 foot Mt. Dana, I enjoyed a nice sunrise at Mono Lake, then I spent another day shooting Yosemite under some nice, dramatic clouds. I started getting a little tired after 36 straight hours of photography, but what a great trip!

With clouds over Yosemite and water levels low and calm on the Merced River, I had a particularly productive time there. Here are a few of my favorite shots.

The turnout opposite Bridalveil Falls is a great place to stop right before sunset as the softening golden light of the setting sun brings out the color in the valley's granite. Bridalveil Falls and the Merced River in Yosemite Valley are at extremely low levels following a winter season of low snowfall.

I wasn't sure if the reflection was going to be strong enough, but as it turned out I really like how the rocky bottom of the river shows through in the darker areas of the reflection. Some people think that all you have to do in landscape photography si show and trigger the shutter, but in this case a circular polarizer at partial strength, a graduated neutral density filter hand-held in front, auto exposure bracketing 3 shots plus HDR processing and Photoshop color adjustment were all needed to create this result

I go to Yosemite a lot, but this was my first visit with a really wide lense. Being that deep in a valley, the extra coverage sure helps, especially if you're trying to double it the Valley's landmarks with a reflection!

I call this photo "PapaBearazzi." Fortunately this bear had plenty of ripe apples to keep him full, but at night the bears roam the campgrounds, like giant dogs, looking for dropped table scraps. I've rarely seen bears wandering around during the day in Yosemite, but on this day I saw 2, and the night before my father stepped out of his tent and almost tripped over one!