When people are first learning about HDR photography, one of the most often asked questions is, “How should I set the exposure bracketing on my camera?” Since this is a function of the camera that many photographers rarely rely on, just getting it set up might seem to be a mystery, but there are manuals for that. (Umm… you did read the manual, right? 8) ) Beyond learning the basics of automatic exposure bracketing (AEB) on your camera, though, there is the question of exactly which settings you’d want to choose for a given HDR situation.
The common wisdom is that you should set your camera to take a minimum of three exposures at Exposure Values of -2EV, 0EV, and +2EV. This works out pretty well for most people and most shooting situations. It’s also about the safest advice that one can give for shooting HDR brackets, as many entry-level and ‘prosumer’ cameras are capable of doing this. There are differences between camera models, though. Some can take five brackets, for example, but only allow for 1EV spacing between them. A rare few allow nine brackets, but be ready to stimulate the economy by shelling out some serious cash for the camera. (To view a comparison of AEB capabilities on different camera models, check here to open the list in a new window.)
Whether you’re shooting the camera’s maximum of three brackets or five, experience has shown that shooting in this limited range does not always capture all the data you need for the best result!
If the scene that you’re shooting has limited dynamic range (here’s an example), or if the sun is at 90-degrees, you can shoot three brackets at +/-2EV and get a decent result. In fact, it seems that the majority of published HDR images use those settings. But, we could expand on that same principle and suggest a new axiom: The greater the dynamic range of the scene, the more brackets you want, and brackets tighter than 2 steps are goodness.
Without getting overly technical, the sensor on each camera model has a maximum dynamic range that it can capture. Within that dynamic range capability, there is a “sweet spot” for each model, a range where the captured data is represented well. (You can get more information on your camera and lens combination at DxOMark.) If the dynamic range of your scene falls outside of those capabilities across three brackets, the resulting HDR image will suffer in terms of blown-out highlights and crushed shadows. In the overall scheme of things, the image will probably still look pretty impressive, but it won’t be all that it can be.
We also need to bear in mind that whatever image we’re viewing, whether it’s a print or on-screen, has been tonemapped down from the full 32-bit HDR to a version that current technology can display, so in a sense, much of the original HDR data is ‘lost’. Given that this is the case, doesn’t it make sense to start with the best possible set of data?
There is now a way to get around the limitations of your camera’s AEB function, and a way to get tighter brackets. I had been hearing about a device called the Promote Control, from Promote Systems, as something that can open up the shooting capabilities of almost any camera. Having heard nothing but positive talk about the device, I decided to get one. Happy, happy… One of the best days we can have is when the B&H box shows up on the doorstep (and you’re fast enough to beat the neighbor to it.)
The Promote Control has several different modes: time-lapse with start delay, one shot, and manual hold, but the mode of most interest to us is the HDR mode. You can read about it on the Promote Systems website, but in short, you can set the Promote Control in HDR mode to take a sick number of bracketed shots, and it allows you to set the EV steps between each in 0.3EV increments. So, if I want to take a bracketed series of, say, 15 frames with 1EV in between each, you just use the buttons on the Promote Control to set it up, then press the Start button.
Some functions of the Promote Control require an optional shutter cable to activate them, such as the Mirror Lock Up (MLU) function, which helps to reduce the vibration caused by the camera’s mirror swinging up on each shot, or for shots longer than the camera’s maximum exposure time, often 30 seconds. In addition, the Promote tends to shoot frames far more slowly without that shutter cable.
Here’s the problem that I ran into: My camera model was not on Promote’s list of cameras that accept the optional shutter cable. In my situation, since I wasn’t terribly affected by the lack of MLU or long-exposure functionality, the biggest problem was the sluggish shutter activation speed without the cable. If I were shooting a large set of brackets on a landscape with moving clouds, by the time the series was done, the clouds would have moved enough to cause ghosting issues in post-processing. Having the capability to shoot wide and tight brackets outweighed that issue enough for me to spring for the Promote Control.
But, it never hurts to ask the question. With an upcoming photo safari in mind, I contacted the people at Promote Systems to see if a shutter cable for my camera model would soon be available (there was a rumor floating around about that.) I was told that, yes, it would soon be available, but not in time for my trip. Bummer.
Over the next week or so, I worked with Max Mamonkin at Promote Systems, and guided by the advice of a friend, to come up with an alternative solution, one which required me to cut into my Nikon MC-DC2 cable release and rig it for my camera, requiring only a 3/8″ stereo headphone jack from Radio Shack. Although the micro-soldering was touchy, we managed to get a DIY cable up and running.
Having accomplished that, Max could have let the issue rest, knowing that I had a solution for my field trip, but he continued on my behalf. Promote Systems received a test batch of the new cables, and Max immediately tested and shipped one out to me. It works like a charm!
Let’s see how this breaks down: A reasonably priced ($299) electronic device with a USB interface for future firmware upgrades that allows a seemingly ridiculous number of brackets at almost any EV interval. Check. Responsive and friendly customer service people. Check. A support specialist that goes above and beyond the call to get this cable into my hands in a timely fashion, in time for a major photo opportunity… Priceless.
I really can’t say enough good about Promote Systems and the people there. They’ve been quite helpful in this process, and I thank them very much.
Note: I am not affiliated with Promote Systems in any way other than being a satisfied customer.