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High Dynamic Range Experiments
Some of the best outdoor photography opportunities can often result in disappointing results. The pictures never seem to look the same as in real life. This is especially problematic in shooting sunsets, backlit shots, and dramatic cloud pictures. The problem is primarily due to dynamic range limitations of photography. Dynamic range is the ratio between the brightest and darkest areas of a scene. Film and digital sensors just cannot capture the full range of light seen in nature. The worst cases are shooting towards the sun at or near sunset, where the sky is very bright, but the land is dark and shaded. Usually, shooting sunsets results in silhouettes, where the sky is properly exposed, but the foreground is black and featureless. Another situation, with somewhat less dynamic range, is shooting scenery with a bright sky and clouds. Exposing properly for the sky and clouds often results in the land being too dark. One way around this is with a graduated neutral density (GND) filter, where half of the filter is dark, and the other half is light or clear. This works well when the horizon is flat. If the horizon has hills and mountains, however, this can result in those mountains being either under or over-exposed. Since the dynamic range can vary greatly from scene-to-scene, you need to carry a set of GND filters with different densities.
There are tricks that can be performed in processing the pictures that can deal with with ranges of brightnesses, but they require skill and are time-consuming and tedious. In more recent years, easy-to-use software solutions have appeared for HDR (for High Dynamic Range) image processing. They use computer software to digitally combine multiple pictures of the same scene taken at different exposure settings to compress the range of light and dark so that it is compatible with monitors and prints. The most common programs for doing this are Adobe Photoshop CS2 (and above) and HDRsoft Photomatix. Photoshop is a professional program and is very expensive. Photomatix is just for doing HDR processing and is much cheaper. You can get a free download of Photomatix. The free version is fully-functional, but it leaves a watermark on the pictures. For $99, you can upgrade it to the registered version that does not leave a watermark.
To take the test pictures below, I used my Olympus E-510 SLR and took multiple pictures at different locations. In most cases, I used a tripod, which gives the best results, but is not absolutely necessary. I used automatic exposure bracketing, varying the exposure by +/-0.7 to +/-1 EV. I used burst shutter mode, which shoots 3 pictures in 1 second at each exposure setting. In many cases, I manually shifted the exposure up and down by up to 3 EV's to make sure I got the full range of brightnesses. I used aperture priority mode most of the time, setting the aperture manually to maintain a constant depth of focus. The camera automatically chose the shutter speed and ISO value. The camera has sensor-shift image stabilization, so I was able to handhold some of the shots, even at a slow shutter speed. I deliberately chose scenes that have a wide dynamic range and are usually difficult to shoot normally, particularly clouds, sunsets, and backlit shots. Since HDR does not do well with moving objects, I tried to avoid scenes with birds, people, and moving vehicles in them. For fast-moving clouds, I had to shoot fast.
I downloaded the trial version of Photomatix. I looked among the multiple pictures of a scene for ones at the extreme high and low end and at least one in the middle. I loaded these into Photomatix. I let it automatically align the pictures to compensate for small camera shifts between each shot, which is essential for the handheld shots. I also let it compensate for background motion, such as water rippling. It then creates a single HDR photograph. An HDR photograph has a dynamic range that is so wide that it is impossible to reproduce it on a monitor. It uses a technique called tone mapping, which compresses the range so that it can be viewed on a monitor. The program has adjustments for brightness, contrast, color, and saturation. See the links below for more information. I tweaked the settings to get the best results. I saved the files as TIF files, which are huge. Each file took almost 30 MB. I loaded the pictures into Photoshop, manually tweaked them for the best appearance, reduced them in size to about 800X600, and saved them as JPEGs. The results are shown below:
La Colina Park
The sky and clouds are very bright. The low angle of the sun creates deep shadows on the hills. With the sky exposed properly, the shadowed areas would normally be black and foreground would be dark. HDR processing keeps the sky properly exposed, while bringing out the details in the shaded areas.
The sun is just to the left of the frame, brightly side-lighting the clouds. Most of the mid-ground is in shade. The foreground is brightly sunlit. HDR processing equalizes all of these.
The sun is behind the clouds, highlighting parts of the clouds, but leaving the foreground in shadow. HDR processing keeps the foreground from getting too dark.
This is shooting directly towards the sun, which is behind the clouds. In a normal photograph, if the clouds and sky were properly exposed, the foreground and hills would be nearly black.
This is another mix of bright clouds, partially sunlit mid-ground, and the foreground in shadow.
Looking across Lake Almaden at the sun backlighting the clouds. The mountains and foreground are in deep shadow. HDR processing allows details to be seen in those shadowed areas.
Some motion artifacts, called "ghosting" can be seen in the leaves on the tree. This is because the leaves moved slightly between successive shots.
Looking along Coleman Road, there are cars and people moving and would normally cause ghosting, but they are removed by Photomatix.
The setting sun shines through a hole in the clouds and reflects off the water. Everything else is in deep shade. HDR maintains detail everywhere.
Only parts of the clouds are sunlit. Everything else is in shadow. The mountains on the right are in deep shade.
Almaden Quicksilver County Park
The Guadalupe Trail (handheld). Normally the hill on the right, which is in shadow, would be very dark. HDR brings out the shadow details.
Mt. Hamilton and the Almaden County Club from the Mine Hill Trail south of the Guadalupe Trail junction (handheld). The mountain ranges in the background are sunlit, while the foreground is in shadow. Normally, if the background mountains were properly exposed, the foreground would be nearly black.
View of downtown San Jose, Communications Hill, Castillero School from the Mine Hill Trail. The foreground looks bluer than the background because it is lit by the blue sky. The picture color balance is set for normal sunlight, so the background looks normal.
Mt. Hamilton from the Mine Hill Trail south of the Senador Mine Trail junction (handheld). This is at sunset, so the mountains are bathed in reddish light, while the foreground is lit by bluish skylight.
Martial Cottle Ranch
The Martial Cottle Ranch is a state and county park that is undergoing planning for development. It is not yet opened to the public, but it is adjacent to urban neighborhoods. These pictures were taken by shooting over the fence in the Vistapark neighborhood.
Sunlight from the setting sun highlights parts of the hills and some of the clouds, while the fields in the foreground are in the shade.
The clouds and hills are brightly lit by the setting sun, while the foreground is in deep shadow.
The clouds are brightly side-lit by the setting sun, while most of the hills and the foreground are in deep shade.
Santa Teresa County Park
The barns at the Bernal-Gulnac-Joice Ranch. This is just after sunset. The sky is still bright, but the foreground is dark. HDR processing equalizes them.
View of Manila Drive from the Joice Trail at sunset.
View of the Almaden Valley from the Bernal Road parking lot. This picture, like almost all the others, was created using a technique called tone mapping.
This is the same picture, but using a method called exposure blending. It averages the exposures, which can result in a less dramatic, but more traditional-looking results.
View of the Stile Ranch Trail
View of the Mine Trail, with sunlight hitting the hills in the middle distance.
Another view of the Mine Trail, with more sun on the trail.
Another view of the Mine Trail, with rays of sunlight illuminating areas in the foreground and background.
Sunset from the lower Rocky Ridge Trail, looking directly into the sunset.
The horse trough at the Pueblo Area near the Mine Trail trailhead, looking right towards the setting sun.
These are the 4 pictures that made up the above picture:
Note that the first picture is the proper exposure for the clouds, while the last picture is the best exposure for the foreground. These exposures have a 3.3 EV total range. The second picture is what the camera would normally shoot if set to auto-exposure. Note that the sky in that picture is a just little too bright, but the foreground is much too dark.
The mapboard at the Mine Trail trailhead, with the setting sun behind the clouds in the background. Like the previous picture, this has a huge dynamic range, but details can be seen in all areas due to HDR processing.
The field in the Pueblo Area at sunset. The setting sun highlights the clouds, but the fields are in shade. HDR processing brightens up the shaded areas.
Pictures by Ronald Horii. Page created 12/21/08, updated 5/26/10.