HDR in Motion: Realistic HDR for Wildlife Photographers
Image 1 : Salt Water Crocodiles Sydney and Maximo ~ A mating pair of captive saltwater crocodiles were photographed at 400 mm with tripod and cable release. Sydney, the female in the foreground is much smaller than her mate due to sexual dimorphism. Under overcast skies with even reflectivity, three RAW auto-bracketed exposures were taken through glass (at 1/2500th ,1/640th , & 1/160thth of a second, ISO 400, F/8, average EV=13.) Photomatix Pro® tone mapping was set to Details Enhancer > Compressor Deep. Tone mapping was used with settings to boost contrast on the crocodile’s scales.
INTRODUCTION: Trying HDR with “moving” wildlife subjects.
The idea of this article is to motivate photographers to try HDR with wildlife subjects. The key is waiting for the animal to pause. In the HDR software, the main goal is to get the highlights correct. The image needs detail in the highlights, especially when it is taken under high-contrast conditions. HDR software engineers have given us brilliant tools to do this. Now we can apply them to make realistic wildlife images without tone mapping artifacts. Shooting in RAW, with a tripod, and processing in Photomatix Pro is my workflow.
Tone Mapping Artifacts
Wildlife and nature photography demands clarity and lifelike color. Tone mapping, technically, means translating a high dynamic range image to display on a device with a much lower dynamic range. Most HDR, or high dynamic range, is tone mapping: the process of mapping a 32-bit floating point image into a bitmap for display . . . true HDR images have 32 bits of brightness information with few limits on how many levels you can represent.
We’ve all seen tone mapping artifacts: hyper-saturated, high-contrast images. Halos and gray clouds are not a sign that a nature image has a wide dynamic range, nor do they fit with the photographic tradition of nature photography. They are artifacts of tone mapping. For wildlife images, natural-looking color is essential, and contrast must be controlled both in capture and in post-processing. For wildlife images, we are trying to get realistic HDR.
Image 2: Galapagos Tortoise.
Three bracketed exposures ( at ISO 200 1/30th, 1/125th, and 1/1000th, ISO 400 f/8 average EV = 12.) with a 400mm lens in overcast November light in St. Augustine, Florida, at the Alligator Farm Conservancy. It is not always possible to get 5 frames in register.
Image 3: Marabou Stork
With a digital SLR set to Aperture Priority mode, I chose F/6.3 because this aperture lets in enough light to expose the slowest of 3 frames at 1/125th of a second ( ISO 200, 1/125th, 1/500th and 1/2000th, f/6.3 , average EV ~ 12) 400mm f/5.6 Canon L lens).
TECHNIQUES : Find the stillness within the movement
1. LOWER your ISO (International Organization for Standardization)
Photograph at the lowest ISO possible to minimize noise in your nature prints. Use RAW file capture at the highest resolution setting on your camera. Use a tripod instead of raising ISO.
2. TURN off the AUTO
Turn off IS/ VR/OS which are acronyms for image stabilization. Yes, it is an amazing tool, but turn it off to register your frames in a bracketed HDR series. With Auto-Bracketing (AEB) set, and Aperture Priority (Av) mode selected, turn off the Auto-focus. Do not use auto ISO, do not zoom, and do not use the self-timer.
3. WHITE BALANCE for the best color
Remember to adjust your white balance in the camera menu. Although Auto White Balance can work well, try Manual White Balance settings with a white/gray card, a sheet of white paper or customized white balance gear. Lightroom or Aperture presets may do this more conveniently for your workflow.
4. SPEEDS, STICKS & STILLNESS for stability
I know from practice that 1/60th to 1/125th is about the slowest range of shutter speeds for stable shots with this 400 mm lens ( Vibration Reduction/Image Stabilization were not used.) A rule of thumb is to choose a shutter speed equivalent to the focal length of the lens. However, most of you reading will be trying even slower shutter speeds because you are using steady tripods or “sticks”.
Even with a sturdy tripod-mounted camera, shutter speeds slower than 1/60th of a second place my setup at risk for both subject and camera movement. So, to minimize subject movement, the main idea is to wait for moments of stillness when the wildlife animal pauses.
5. STICK with It.
Be persistent. When photographing a restless animal, it will take more tries to get a sequence of three identical bracketed images. To do this, wait for those short slices of time when the animal pauses for a split second. Expose your frames. Then, hang around for the next “in-between” moment and take yet another bracketed series. Practice on captive animals first, then move to wild ones for more adventure.
Take off your watch and slow down. Be on “animal time.” Think about how the animal feels and moves once it sees you. At first, stay far away and watch. Then, slowly, after the subject settles a little, approach stealthily, crouch down, and be still. Lower your lens to the animal’s eye level.
WORKFLOW for Realistic Wildlife Images
Because HDR software needs identical frames, any differences in the bracketed images makes it harder for software to align the frames. “Ghosting” happens when the subject moves between frames of a series of multiple exposures. Correcting ghosting artifacts takes time. Software programs have built-in ghosting formulas but running them discards some exposure data as it applies only single exposure information to parts of the entire photograph. Prevention is better than treatment.
Image 4: Camera RAW Photomatix Image Editor Workflow
This sequence is a workflow for processing a bracketed series. The initial RAW conversion is done in Adobe Camera RAW to maximize the information that goes to Photomatix Pro, the HDR software. In Photomatix, Exposure Fusion > Adjust and Tone Mapping> Tone Compressor with minimal saturation are settings for realistic color. For the finishing touches, use your favorite image editor : Aperture, Lightroom, Photoshop.
The workflow in Image 5 needs some definitions. Looking more closely at the Photomatix Pro settings helps understand an HDR workflow. Tone mapping has some basic settings.
Tone Mapping > Tone Compressor
The image below of the white egret was processed with Tone Compressor. Compared to Details Enhancer, Tone Compressor can produce a more realistic look to tone mapping by preserving shadow tone and color. Tone Compressor also allows more control over the range of tones, often needed for images of wildlife.
Tone Mapping > Details Enhancer
Many of the Photomatix images we see online are processed with Tone Mapping set to Details Enhancer. Details Enhancer boosts both contrast and detail, opens up the shadows in an image, it can add a painterly or surreal look to images. I use it only with specific images. Occasionally, some highly detailed images that I shoot in bright sunlight can benefit from Details Enhancer.
In Photomatix Pro you can choose between Exposure Fusion and Tone Mapping. Again, Tone Compressor and Details Enhancer are options for Tone Mapping.
Image 5: Great White Egret Example of preserving feather detail with Tone Mapping > Tone Compressor Setting.
When I saw this egret at 4:30 pm on a June afternoon in Fort Myers, Florida, it was relatively motionless. At ISO 100, f/6.7 and three bracketed exposures, the challenge was to preserve detail in the feathers. So, tone mapping was set to Tone Compressor to preserve these off-white details.
African Crowned Cranes
Two cranes touch beaks, perhaps in courtship, in St. Augustine at the Alligator Farm Conservancy. Tone Mapping with Details Enhancer kept the textures in the birds golden crown. To preserve overall lighting, the Photomatix Lighting Adjustments slider was set to Natural by first checking the Lighting Effects Box.
These cranes moved their necks so often, I was thinking I might get motion blue, so I raised the ISO up to 500 to minimize the capture time of the three frames ( ISO 500, Aperture f/7.1 ,3 auto-bracketed exposures.).
Image 6B: Closeup of the cranes.
Arguably, there is no such thing as good light and bad light. There is only light. Some of the images in this article were made under overcast conditions with a exposure value range of less than 5. While it is tempting to take just a single exposure under cloudy conditions, shoot at least 3 bracketed shots to practice your HDR methods and learn how to process them. Cloudy days can also be superb times to create B/W HDR (see my article here.)
All lighting conditions are worthwhile for trying the Exposure Fusion settings in Photomatix. While I try to avoid bright sunlight to photograph wildlife, in the field “it is what it is.” For overcast days with a low dynamic range, the Exposure Fusion setting may work better, although Exposure Fusion can result in poor local contrast when the dynamic range of the scene is high. When there are deep blacks and bright whites in your scene, try the Photomatix Pro Tone Mapping > Details Enhancer and lower the saturation and contrast.
Before you expose a bracketed series, ask yourself:
“Where is the light on my wildlife subject coming from?”
“Should I move to get a better direction of light?”
“Am I shooting under the soft light of a cloudy day or under high contrast sunlight?”
“Can I use my spot meter to meter the shadows and the highlights so I know what the range is in my scene?”
In the field, practice your HDR skills in a variety of lighting conditions, with low contrast and high contrast light. Remember to use a wider range of stops when you bracket exposures in high contrast scenes. Your experience and preferences will guide your workflow decisions.
PHOTOSHOP WORKFLOW: The Photoshop Layer Cake
Adobe Photoshop tools are valuable. They help restore details you first saw in with the wildlife. For natural results, I use layers. Photoshop’s layer adjustments are valuable tools, especially when printing. If a print is not accurate, adjustment layers can be easily changed. Another advantage of using Photoshop adjustment layers is that they can be created above a layer that holds your HDR layer. Adjustment Layers are easily deleted, modified with a different layer blending modes like soft light, and they can be archived as master .psd files. They are also useful to correct color casts.
Here is an example with a wild, wet and weary great horned owl on Cumberland Island, Georgia, USA. It shows adjustment layers used to correct a blue color cast.
Image 7: Photoshop CS5 Layers
Great Horned Owl, Cumberland Island, Georgia.
The upper adjustment layer corrected a blue cast from a cloudy sky that was near the Atlantic Ocean. Photomatix Tone Mapping > Tone Compressor > Default settings were used to tone map three RAW files. Saturation was also reduced in the middle adjustment layer.
In the Photoshop part of the workflow, it is a good practice to add adjustment layers for Hue and Saturation, Levels, Curves and any other adjustment, then save .psd (Photoshop Shop Document) master files with your edits.
Another valuable practice is to combine two images in Photoshop layers. Instead of burning and dodging, layer two different HDR images, each with a different process. For instance, an Exposure Fusion > Adjust layer can be combined with a tone mapped layer or even the initial Tiff file.
Image 8: Photoshop CS5 Layers, Wood Stork
Instead of burning and dodging, two images were processed in Photomatix Pro, then placed into the layers palette of Photoshop CS5. The top layer is an image processed with Photomatix > Exposure Fusion > Adjust. The bottom layer was Photomatix > Exposure Fusion > Default. The Photoshop layer mask on the top layer corrects both the highlights and the shadows. The tops layers blend mode, Soft Light, lowers the contrast of highlight and shadow with the wood stork.
GEAR : Know your range. Add tripod, cable, and fast glass.
Like bees from a hive, digital cameras fly out of the factories each month, featuring faster capture rates, built-in HDR modes and smaller and more sensitive CMOS sensors. With more internal electronics, built-in HDR options are included in point-and-shoot and smart phone cameras like the iSight camera on the iPhone 5 . You can enjoy the new machines and still learn how to “see in HDR” now.
Start by asking yourself: “What is the dynamic range of my camera?” For instance, my old Canon 7D DSLR has a effective dynamic range of about 8- 8.5 F-stops (compared to the Red camera with 9 and our brain’s visual system that has a range of almost 24 F-stops.)
ISO & RAW PROCESSING
Put simply, dynamic range is greater at lower ISO speeds than higher ones. Specifically, for ISO 100, the sensitivity overall is 8.3 EV, with highlight range sensitivity rage at 3.3 EV and shadow range at -5.0 EV. So, I to dial in as low an ISO as possible and then process in Adobe Camera RAW before exporting TIFF files to Photomatix. Manually processing in Adobe Camera RAW maximizes the dynamic range and with the Canon 7D, this approaches 10 stops.
SHUTTER SPEEDS & BURST RATES
Wider apertures allow for faster shutter speeds. These are needed to capture active nature subjects – not for creating shallow depth of field – but rather to ensure both faster shutter speeds and shorter total capture time when shooting in bracketed bursts. When shutter speeds are too slow and the shutter is open too long, the time it takes to make three exposures gets longer. The animal must be very still under these conditions. Many wildlife subjects will move in that fraction of a second. This makes the digital frames go out of alignment creating ghosting artifacts. To avoid ghosting, using a stable tripod and camera with a fast burst rate (5-14 frames per second is ideal.)
Some photographers use fast-capture hybrid/mirror-less cameras. Those that have low-noise sensor are generally more effective for HDR. With a few exceptions, most point-and-shoot cameras, although they now have burst capture rates that are adequate for HDR, have too high signal-to-noise ratios. You get unacceptable noise, or grain, in the shadow areas.
All variables including aperture, ISO, the camera and the subject itself must remain unmoved during picture taking. Only the speed varies between exposures.
SPECIAL SECTION: Slowing down the Shutter
Image 9: American Alligator with Slow Shutter Speed HDR
For this image, a slow shutter was deliberately employed. Captured RAW, in color, with the camera on a tripod, the American Alligator image was processed with three bracketed exposures ( 4 sec, 1 sec, ¼ sec ). Photomatix Pro version 4.1.2 settings used were Tone Mapping > Compressor > Default > Black and White.
First, I took a meter reading. In the overcast light, a spot meter reading indicated that 4 seconds would be the longest shutter speed, giving an exposure that I believed would pull detail from the shadows. I chose a small aperture in Aperture Priority (Av) mode at ISO 100. Because this gator was motionless, it was an ideal subject for trying a long, slow shutter speed to blur the water from a nearby inlet.
Nature and wildlife photographers have choices. To honor the craft, images can be processed with a subtle touch. It is easy to overdo the magic of the tools with too many spells; over-saturation, over-processing and tone mapping artifacts. To resist the urge to process pictures with tone-mapping artifacts is a challenge for creative digital artists and thoughtful nature photographers, but nature has her own wisdom and we have options to employ our tools while guided with a more natural vision.
FAQ: What is exposure value ?
An increase in one exposure value (EV) corresponds to a doubling of exposure. EV is a number that shows combinations of shutter speeds and apertures that give the same exposure effect in scenes with similar brightness and ISO. For instance, at ISO 100, the combination of a 1 second shutter speed and an aperture of f/1.4 is defined as EV 1.
EV also indicates a range of sensitivity. The lower the number the more sensitive a meter is to light. EV is a scale of values that shows how sensitive a built in metering system or off camera meter is. On a 35 mm SLR, an EV range might be EV 3 to EV 18 or EV -1 to EV21. For an EV table, see Bloch, Bethke, Vogl, Steinmuller 2010 The HDRI Handbook: High Dynamic Range Imaging for Photographers and CG Artists, page 82 and Fred Parker’s website at http://www.fredparker.com/ultexp1.htm