Summary
Technical saga, for
the uncontrollably curious...
This picture is a 110º x 70º wide-angle panorama, produced from eight 35-mm negatives by extensive digital processing. The original negatives were shot with a nominal 28-mm lens, but the final geometry is roughly equivalent to what would be produced by a 16mm lens projecting onto a 30x24mm piece of film wrapped around 110º of a cylinder. Warping the eight original hand-held images (two rows of four images) to form a seamless composite was made relatively straightforward using the PTGui off-the-shelf software package (www.ptgui.com) with a set of 65 control points. A more serious challenge was presented by the very wide range of brightness present in the original scene – from white snow in full sun to dark foliage in deep shadow. This was handled by scanning the film negatives at low contrast to capture detail in all areas, then using a set of eleven Adobe Photoshop masked adjustment layers to alter the brightness, contrast, and color balance of each area as needed to provide an overall pleasing effect. Since this still resulted in fairly low local contrast, a wide “unsharp mask” was used to improve local contrast and crispness before printing. A certain amount of manual painting was required to eliminate film blemishes and timestamps, and to extend plausible detail into a couple of corners where the original negatives did not have quite enough coverage to give the desired overall wide-angle view. The final images were printed as 16x20 inches at 305 dpi by Robyn Color (www.robyncolor.com) on Fuji Crystal Archive photo paper. Time spent working on this project was treated as amusement and was not logged; it was probably around 100 hours.
The following images illustrate some major steps in the process.
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This scan of a physical paste-up illustrates the very wide range of brightness to be handled. The need for nonlinear geometry correction (warping) is obvious in the foreground snow and rocks. |
This “Panorama Editor” window from PTGui shows the result of geometry correction. The low contrast from scanning is preserved at this stage |
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Masks for each of the eight input images and painted regions are shown here. Major corrections for brightness, contrast, and color balance have been made at this stage. |
Masks for the sky, sunlit terrain, and foreground shade are shown here, along with the effect of brightness and contrast corrections for these areas. |
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The final image, after “unsharp masking” to increase local contrast and crispness. |
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--Rik Littlefield,