Monday, October 8, 2007

Nocturnal Photographic Trivia

Over the previous few months, I've made a number of visits to the Bamberger Ranch for purposes other than taking new photographs; mostly picking-up panoramas from the Kirchman Gallery in Johnson City, where I've been having them printed. It is my usual practice to make the drive more pleasant by doing at least the outbound leg at night, then catching some sleep in the guest quarters (when available), and getting on with the business of the day whenever I regain consciousness. I usually bring along all of my photographic gear just-in-case. On several of these visits the "just-in-case" has been "just-in-case I arrive there early enough to try shooting a moonlight panorama, before I absolutely have to get to sleep".

All of those moonlight panoramas have been complete failures, because they turned-out so clear and colorful that they look a lot like they were shot in the middle of the day. I more-or-less expected that, but figured that I could add the "moonlight look" after the fact by playing with colors, levels, etc. That failed, too, probably because the way that the camera's sensor and the human eye's retina experience these low-light conditions are very different. There may yet turn out to be a way to get the look that we humans expect by processing the images after the fact, but I'm not optimistic at this point.

So, I pass along my failures for your amusement:

The panorama above was shot halfway up a valley wall in the region of the ranch known as Wildlife Preserve. Crossing valley-bottom streams and climbing by the light of the moon and a small red-LED flashlight was very time consuming and a bit dangerous. Nonetheless, I was eventually able to reach a spot very near where I had shot a panorama two years ago. That time, it was broad daylight and the exposures were trivially short. This time, there was a full moon, elegantly obscured by clouds, so I could only obtain reasonable exposures at f8 by using ISO 800, and a shutter speed of 2 minutes. With the camera taking an additional two minutes to perform noise reduction on each image, each shot really took 4 minutes, and therefore the whole, six-segment pano took about half an hour to shoot, and a lot longer if you include the time spent on various test exposures. As you can see, nothing about the image suggests that it was shot between 5 and 5:30 in the morning, exclusively by moonlight.

From one of the test exposures, above is a sample of the wonderful texture of the clouds that night. Unfortunately, little of that texture comes through in the panorama because the longer exposures used for those images allowed the steadily moving clouds to become undifferentiated blurs.

While I stood up there on the valley wall, waiting for the camera to do its job, there came a moment when I heard a descending whistle sound from one of the four or five valleys that open onto that scene. For some reason, I associated that call with a Great Horned owl (I'm not sure that's right, but that's what I thought it was at the time). With nothing else to do, I thought I'd try to call the owl over to me. Since I can't imitate any Great Horned calls, I settled for my iffy impression of a screech owl call, knowing that Great Horneds will gladly make a meal of screech owls. I never did see any evidence of a Great Horned owl, but I was surprised to find that my lousy screech owl impression was answered by at least one pair of screech owls in each valley. I knew screeches were in the area, but I was surprised to find that there were so many.

The failure of the previous moonlight panorama notwithstanding, on a subsequent visit I tried again by the light of a ¾ moon, and this time at the mouth of the chiroptorium, the artificial cave that the Bambergers built in an effort to establish a large bat population on the ranch. After a rocky start, the chiroptorium has become a complete success; the last bat count put the population at around 120,000. And what could be a more appropriate time of day to shoot a panorama at the mouth of a bat cave than the middle of the night? So I setup there, with bats hurtling all around me, and after a time-consuming series of test shots, began shooting the pano starting at 3:56 AM. To achieve acceptable exposures at f8 and ISO 800, I had to settle for a shutter speed of five minutes. Add to each of those exposures a further five minutes of noise reduction processing by the camera, and it took a full hour to shoot the six segments. Unfortunately, ten minutes gives the moon a lot of time to move, and that changed the lighting noticeably from one frame to the next. Those changes give rise to the obvious intensity differences in the sky at the frame boundaries. (There'd be some of that anyway, due to vignetting in the lens, but let the light source change its position with respect to the camera, and the problem is compounded.) And, it goes without saying that, once again, the pano looks like it was shot in daylight.

It also goes without saying that the panorama includes thousands, perhaps tens of thousands, of bats. Only one bat held still long enough to be recorded in any of the images, but, believe me, they were there. One of the many nice things about working amongst all those bats was what wasn't there: mosquitos. Despite a pair of nearby ponds that should have been producing mosquitos in quantity, I was bothered by only two in the hour-and-half I spent there. As a mosquito attractor, I may have even been providing easy pickings for the bats that raced all around me; some returning to the cave, a smaller number emerging, and many others just swooping through the area.

One of those mosquito producing ponds provided the other great pleasure of that shoot; a chorus of leopard frogs. Their voices often sound a bit like a pair of inflated rubber balloons being rubbed against each other. Whimsically, I was left thinking that the species has been trying to sing with all its might for millions of years, but still hasn't managed to get the hang of it. And, I thought, on some distant night when they do, at long last, get the hang of it, these ponds ought to put the world's opera houses to shame, due to the cumulative effect of all that practice. My peculiar ponderings aside, the lady leopard frogs obviously find the singing appealing, so the fellows are doing something right. And I can't help but smile when I hear them, so I suppose I agree with the ladies.

Lastly there's the above experiment in long, night sky exposures on a moonless night. I had to guess at the pole star's location from some short, test exposures, and didn't get it exactly right, but I was in the neighborhood. That shot was a 45 minute exposure at 10 mm, f4 and ISO 400. Once again, noise-reduction processing after the exposure took as long as the exposure itself, so that was 90 minutes of continuous work for the camera, which makes it important to start with a freshly-charged battery. Fortunately, the noise reduction process works fine even with the lens cap in place and the camera standing at the end of a bed burdened with a snoozing photographer.

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