Photographers have struggled with limited dynamic range for as long as there have been photographers. Expose for the highlights in most scenes, and you will end up with crushed shadows where no details can be extracted from the inky blackness. Conversely, if you expose for the shadows, the highlights will blow out, leaving nothing but garish white the absolute absence of detail. To capture the broad range of light in many scenes, photographers use High Dynamic Range (HDR) processing to combine multiple images shot at different settings into one image with intact highlight and shadow details.
HDR processing can be done in many modern digital cameras, (and even smartphones), but to maintain creative control most photographers opt to use computer-based software to manage the merging of base images and nitpick the fine details. There are many wonderful software solutions out there for HDR processing, but none will work properly if the base images aren’t captured correctly. This article is about creating base images of the highest quality. Later Photofocus articles will tackle the processing side of HDR photography.
Let Your Control Freak Flag Fly
DSLR or mirrorless, it matters not which style of camera you use to capture your base images. What does matter is that the camera you choose must be capable of manual exposure control. Most cameras feature automatic bracketing, which at first glance seems like the perfect option for HDR work. I have found any modes that allow some automatic exposure adjustments will inevitably be fooled by tricky lighting. Opt for fully-manual control and know that any mistakes made will be yours and not some faulty algorithm deep inside your camera.
Cameras and lenses that also allow for manual focus control will also mitigate any errors that errant focusing will cause. Our goal in making HDR base images is complete lockable control. Choose gear that will allow you to achieve full control. HDR work is slow, deliberate and careful work. Anything less will leave you head in hands in front of your computer wishing for a time machine so you could go back and get it right.
Lock It Down
Most HDR software will align images for you, but to play it safe a stable tripod is the best option for HDR image capture. The fundamental idea behind HDR processing is the merging of multiple images. Whether it be two or 12 images, having those images framed identically will allow for flawless merges. A solid tripod and head will allow you to lock down your camera and focus on making great exposures. I find fully manual multiple-image photography is kind of like juggling; the fewer items you are fussing with will make the entire experience much more pleasant and wildly more successful. To capture shadow detail in many situations, longer exposures are necessary, making the tripod a must.
Beware of Ghosts
Because HDR composites require multiple images, you should look for a composition with static elements. Anything moving in your shot will appear in different places in each frame, creating what are called ghosts. These aren’t friendly ghosts and they will haunt your processing and drive you to fits of frustration. Most HDR processing programs have ghost reduction features, but they are limited. The best way to handle ghosts is to avoid them. If you are shooting a landscape with moving water, clouds and people, consider using neutral density filters to drag out the exposure times. Shutter speeds of longer than 10 seconds will make moving people disappear, moving water smooth out, and moving clouds streak into softness. Of course, longer exposure times will require even more diligence with a stable tripod and remote shutter release. If long exposure times aren’t possible, you will need to utilize software to remove the ghosts. In those cases, I would encourage you to make several extra frames to ensure you have plenty of data to work with.
Focus and Forget It
Autofocus is a marvel of modern technology, but in multiple image HDR work, wandering focus points will ruin the party. As you lock your camera down for your base images, switch over to manual focus, (and while you are at it, be sure image stabilization or vibration reduction is turned off). I prefer to use my camera in Live View when on a tripod, and manual focusing in Live View is easy. On my Sony A7R Mark II I employ focus peaking and magnification to fine-tune my focus. If your camera allows for Live View, it will allow you to magnify your shot and check focus. In HDR photography a deep depth of field is often preferable. Hyperfocal distance focusing techniques will give you maximum depth of field without forcing you into diffusion-inducing small apertures. With most lenses, you will enjoy the best image quality in the f/8 to f/11 range, but my Zeiss Batis and Canon L-series lenses, can achieve incredibly sharp images at f/16. Choose your aperture setting and focus point and lock it down. If your lens focus ring is easily moved, I recommend using a small length of gaffers tape to secure it. If you are using a zoom lens, and you want to be sure it doesn’t change focal length you should tape that ring down too. I keep -inch gaffers tape wrapped around my tripod leg for just such occasions.
Sweat the Small Stuff
With composition, focus and aperture all locked down, it is time to set the rest of the variables. Start with white balance. I usually keep my camera on Automatic White Balance (AWB), but when it comes to HDR work I switch over to daylight or cloudy day, depending on the color temperature I am dealing with. I always capture my images in raw format, and I can and will fine tune the color balance in Lightroom later, but locking down white balance mitigates any funny business changing light conditions may bring. With white balance locked down, I move on to ISO and lock it down as well. For optimal image quality I will use the lowest ISO possible. Most of my tripod-based work is shot at 100 or 200 ISO. Whats important here is the consistency across your multiple base images. By locking down focus, aperture, white balance and ISO I can ensure this consistency. The lone standout in my settings workflow is shutter speed.
Speed is the Only Variable
The entire purpose of multiple base images is to capture a broad range of light on a scene, so each base image should be different, but not too different. Weve locked down everything but shutter speed in a deliberate effort to control the consistency of our base images. By varying the shutter speed of each shot, we will be making them darker and lighter than each other. This process is called bracketing and back in the Good Old Days we would employ bracketing to be sure we nailed the exposure on a shot. The logic back then was simple: by firing off several (usually three) shots at various exposure settings, one would be right. This method of machine-gunning worked great with film. Because we had no LCD or histogram to check, we sprayed and prayed. Many, many over- and underexposed shots were binned in the process.
In HDR work, we bracket not to find the best exposure, but to blend several into the best. The quantity of bracketed shots is determined by the breadth of the light in the scene. In bright sunlight, it may take nine shots to cover the range between highlight and deep shadow. I use the histogram in my camera to figure this out. Its not rocket science.
Histograms are Our Friends
With my camera set up for the HDR shot, I turn on the histogram display and adjust the shutter speed until the right edge of the histogram curve nudges against the right edge of the graph. This exposure will be for the brightest portions of the scene, those lovely highlights. This will be a dark shot on my LCD screen, but the goal here is to protect the highlight data. On my camera I know that three clicks of the shutter speed dial changes the exposure by one stop. With my highlight shot in the card, I click up one stop and take the next shot. I repeat the process in one-stop increments until the histogram no longer touches the left edge of the graph. This shot covers the deepest darkest shadows in the scene and depending on the light this shot may be quite long. In the final shot, the highlights will be completely blown out, but it’s the shadow detail that’s vital here. I want the shadows to not be pure black, but instead contain some data. With my bracket of base images in the card, I review them on my LCD screen to be sure I captured sharp images. In review mode on the camera scrolling through the bracketed shots quickly should look like a lightening video with no differences between the shots but brightness. If my shots pass muster, I move on and make more bracketed sets because HDR images are like cookies: one is never enough.
Moments of Zen
I find the process of capturing HDR base images soothing. The slow, deliberate and precise craftsmanship of manually capturing multiple images cannot be rushed. In many ways, HDR photography is like Bonsai gardening. Through careful and patient grooming, a natural scene can be presented in a creative way that exudes precision and passion. I much prefer the capture side of the HDR process. Once my base images are in my computer, the task of merging and processing them feels more like work to me. Perhaps that is why I have hundreds of HDR images in my to-do pile!