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| Light in the Dark: Fort Point San Francisco |
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Directly under the famous San Francisco Golden Gate Bridge is the Fort Point National Historic Site. This fort was built to protect the SF Bay from the Confederate army during the U.S. Civil War, though as far as we know it was never used in military operations. Today Fort Point is open to visitors three days per week and we have taken quite a few photos there over the years.
The challenge taking interesting photos at Fort Point is the high dynamic range (light from the outside and quite dark structures) and the need for ultra wide angle lenses. We deal with the high dynamic range using HDR techniques (later more) and the Distagon T* 2,8/21 ZF on a Nikon D700 full frame camera was ideal to photograph the interior architecture. We were very pleased that all the scenes we wanted to capture could be photographed using the Distagon T* 2,8/21 ZF lens. One could say that 21mm seems to be a very good focal length for indoor photography in general. It has a wide angle of view of 90° without getting to the extremes. Wider angles can lead to more distortions than we would like to accept.
Taking HDR photos requires taking multiple exposures from a sturdy tripod. An example of a typical exposure range is shown here:
For this kind of scene we need at least 3 shots with -2,0 to +2,0 EV exposures (more could be even better). As you can see in the middle exposure, the shadows are too dense and the highlights are blown-out. Even the -2,0 EV underexposed photo still has slightly aggressive highlights. The +2,0 EV overexposed photo shows good shadow detail, but the highlights are lost completely. That the Distagon T* 2,8/21 ZF is a manual lens is not problem at all, because these kind of photos are always best shot using manual focus. We generally used a hyperfocal setting for the photos at Fort Point, because there was not any interesting detail closer than 2m and we used f/8 for nearly all our photos.
We use the Photomatix software to combine these three photos into one HDR image. HDR images (32 bit floating point) can store a tonal range that is even much higher than we needed in this case. What to do with these HDR images if their content cannot be printed on any medium? The answer is Tone-mapping. We use the Photomatix Details Enhancer tone-mapping tool to map the larger tonal range into a printable version. Here is our result from this two-step process (HDR generation and tone-mapping):
The final image shows open shadows and no clipped highlights. The next photo was from the same session and created using the same technique.
Overall we can report that the Distagon T* 2,8/21 ZF on a full frame camera and HDR with Photomatix proved to be the right tools for our work at Fort Point. We plan to work more using this lens and apply its angle view on our subjects.
After our session inside of Fort Point we took this shot of the Golden Gate Bridge just outside of Fort Point. It shows that 21mm can be a very creative focal range.
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| Gate to Golden Gate |
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Text and photos by Bettina and Uwe Steinmueller
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July 2009 |
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