Redwoods in the Fog - the Print(May 5, 2008)
For over two years now I have been making slow deliberate progress towards selling panoramic prints of the images on my Virtual Guidebooks site. My wife has had several of them framed and hung them at home, and I have shown a number at lectures and art fairs. A later blog post will announce availability and give details when my fine art panoramic prints are ready for sale.
Most of the prints I have made so far are straighforward wide-format panoramas, usually the complete 360°. They have an interesting distortion, a unique form factor, and people seem to like them. Since I draw them directly from the 6000+ archive of Virtual Guidebooks images the range of subjects and locations is enormous - something for everyone.
But some of my most dramatic VR panoramas are cubics, which pose special problems for printing as flat media. Here is the story of how I dealt with this challenge for one of these (from the Virtual Guidebook to Redwood National Park) - be sure to look straight up:
The original photos were taken near the dedication site in the Lady Bird Johnson Grove, Redwood National Park, California. A foggy day was chosen both for the soft even lighting and because of the close ecological relationship between the coastal fog zone of northern California and the geographic range of the redwoods.
Some of the trees here are over 300 feet tall (100 meters) and 10 feet diameter (3 meters). Visitors to old growth redwood groves are struck by the cathedral-like quality of the forest and the majesty of the amazingly tall straight trees. Although over 90% of the original redwood forest has been logged, many of the finest groves are preserved in national and state parks.
Below the massive redwoods (Sequoia sempervirens) grow tanbark oaks (Lithocarpus densiflorus), California rose bay (Rhododendron macrophyllum), salal (Gaultheria shallon), and sword fern (Polystichum californicum).
In its print form I call it simply "Redwoods in the Fog". After printing it a few times at home I made a larger print (60 by 30 inches) on the big Epson 9800 at my computer lab. Here I am posing with the final mounted print on the balcony at the Geography department, UC Berkeley.
This striking image began with a series of 37 separate photographs. They were taken with carefully controlled geometry using a tall tripod and a special camera mount. Because of the shoulder-high sword ferns the camera, a Nikon d100 digital SLR, was held about seven feet (2.1 meters) above the ground.
Here the original photos are shown arranged in three tiers, plus a zenith (straight up) shot. There is no nadir shot (straight down) because the dense vegetation made it impossible for me to step out of the way.
Using a special computer program (PTGui) the individual frames were warped and overlapped, then blended, to form a continuous image that covers an entire spherical view. Image procesing programs such as Photoshop can only deal with a rectangular matrix of pixels, so the spherical image was reprojected and saved as an equirectangular image - twice as wide as high, equivalent to an unprojected world map (known as plate carée).
This equirectangular image was then processed into a digital movie file. This uses a cubic imaging model, so the equirectangular image is reprojected to six cube faces.
Viewing software allows the user to direct the view in any direction, unwarping the image in real time for a realistic geometry. This is what you see on the web site.
Note how the equirectangular image completely fails to convey the impression of great height that is so striking in the interactive version, and also when you are there in the redwood forest itself. To approach this ideal on a flat surface a distortion of the spherical image is needed, a problem similar to that of map projections.
First I explored traditional map projections. The Mercator projection results in straight and parallel tree trunks, but it is unable to show the zenith - just as a Mercator world map cannot show the poles.
Other map projections gave interesting results, but my final choice was a filter designed to make fisheye lens images rectilinear. The "de-fished" panorama shows all the way from the photographer's toes to the zenith high above in the fog, with an interesting outwards bowing of the straight tree trunks.
Another way to display a spherical image is to project it to a series of facets which can then be cut out, folded, and assembled into a three dimensional display. It is shown below as a "philosphere", with square and triangular faces.
I would like to do this on a large scale so it could be viewed from inside. A philosphere would be simple, but the more facets the closer it would be to reality. The hole at the bottom is where I was standing when taking the pictures (the missing nadir shot).
If this polyhedron were large enough, and lit translucently from outside, the viewer could stand up through the hole and receive a realistic impression of being in the redwood forest.