Feb 16, 2009

Bosque Delight

Bosque Serendipity, Bosque del Apache, New Mexico

©Joe Bridwell
Sandhill Cranes seek night’s peace as they land and settle in for dark. Our result is a soft, cloud capped sunset where cranes seem to stand silhouetted in orange bas relief… The Bosque del Apache is world famous for such views.
Nikon D300, 24-105, 105 mm, iso 200, f6.3, 1/50, 1/100, 1/25 ~ 14-bit
We captured 3 HDR raw files three minutes after sunset, then processed in Photomatix and Lightroom 2.

Camera v Eye
Our eye sees much better than a digital camera. We instantly record all nuances in a scene, yet our camera only captures a limited portion of scene. When we automatic exposure bracket, we capture a range of contrasting light which is called high dynamic range HDR. With software, our computer can ‘add’ these images together to produce an approximation of what our eye saw.

Most digital HDR shooters use Photomatix Pro. It adds two images together, then asks you to Tone Map. There are 2 variants; Detail Enhancer (DE) and Tone Compressor (TC).
This is a Magic Hour shot (that hour around dawn and dusk); strong dark foreground and light sky. Of course, its complicated by water’s reflection – but it’s this enclosing reflection which adds so much to the sandhill’s charm.

When one compares histograms, Detail Enhancer gives one HDR histogram profile – this profile is not in concert with the 0EV manual capture histogram from the 1st HDR image. Basically, DE moves the original histogram capture from Shadows to Lights – seeming to blow out the HDR compilation.
Tone Compressor gives a histogram pattern similar to 0EV capture.

HDR Histogram - Photomatix Tone Compressor Histogram

We save the 32 bit TC file as a 16 bit tif for further clarification in Lightroom.

Photomatix provides global controls for changing luminosity, tone, and other parameters. Because subtle light variations can decidedly enhance this HDR image without making it ‘science fiction’ in appearance, we will only take the TC product and more subtly tone map it in Lightroom.

Lightroom 2
Lightroom 2 allows local brush control on restoring the resulting HDR image to what our memory saw by eye.
We begin by making Virtual Copies of our HDR tif file (Ctrl-‘) – to allow future growth. Each change we wish to make in Lightroom becomes its own slightly improved baby; for me, my mind changes over time and software improves over time, so this is a good workflow.
With our Tone Compressed file, we change exposure then added clarity and virbance using Lightroom sliders in the 1st copy. Copy 2 allows us to make Medium Contrast using Tone Curves. Copy 3 lets us work with graduated filters. Copy 4 lets us try to reduce bird motion caused by the time difference in taking individual HDR images using the local adjustment brush. This last step is like burning in the shadows left when birds move their heads in search of food. Copy 5 lets us sharpen the result.

Final Image
After we complete Lightroom's Develop module steps, we return to the Library Module and Export the ‘final’ image as both a DNG and jpg file. Meanwhile, our Catalog contains all history changes for each copy. Both files are placed in a laptop portable Catalog we used for this particular project development.

We developed this HDR workflow approach based on knowledge of how histograms reflect the reality of capture, what different global tone mapping tools might or might not do, and the marvelous precision attained with new local, nondestructive brush tools in Lightroom. We executed our local Tone Mapping changes on a Wacom Pen Tablet using current upwardly mobile software tools – which we expect to only improve.

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