By Brian Matiash, Photographer
Hello. My name is Brian and I love HDR.
Ok. It has been said. So, what do we do now? Well, I figure that if you're going to obsess about doing something, at least obsess about doing it the best that you can. And that is what my hope is with this post - to share the knowledge that I've picked up over the years shooting brackets for HDR imaging.
I recently had the opportunity to present on HDR Photography to a group of photographers and one part of my presentation dealt with the best practices that I follow every time I go out to shoot for HDR, as well as when I'm at home processing the shots. It turned out that this part of the presentation was very well received and so I figured that it might help to share these tips here.
This particular post will focus on tips that I've learned while out in the field. I hope it all helps. Feel free to leave a comment or reach out if you've got any questions.
Best Practice #1: Know What HDR Is
I think that it's generally a good practice to know what it is that you are about to engage in before actually engaging in it. Without rehashing the plentiful (and often very helpful) tutorials out there that define what HDR imaging is, here is my take: the dSLR cameras on the market today are pretty amazing and can do plenty to capture beautiful images. Still, they are limited in how much dynamic range can be captured in a single exposure. At a superficial level, the dynamic range of an image is all of the information in a scene that ranges from the darkest shadows through the mid-tones and into the bright highlights.
The typical dSLR camera will be able to capture most of this detail when there isn't too much dynamic range, say in a living room during the night and lit with various lights. However, come back to this room during high noon and draw the shades open and now you've got a scene that has a ton of dynamic range. With your camera and a single exposure, you basically have to pick and choose what will be metered and exposed for and sacrifice the rest of the scene. Choose to expose for the interior and watch as the outside detail resembles something of a nuclear holocaust of blown out information. Have a change of heart, choosing to meter for the exterior, and the living room will likely be underexposed and barely visible. Now, I understand that you can lug around strobes, modifiers, power supplies and the works to get proper exposure for the whole scene but you'll probably be better off hitting up some other sites if that is the case.
With HDR imaging, you generally take several exposures of a scene that has a lot of dynamic range, ensuring that your shortest exposures have detail in the brightest areas as well as ensuring that the longest exposures have detail in the darkest areas. In post processing, tone-mapping software analyzes each image, pixel by pixel, to provide you with a tone mapped image. I'll go into more detail on this in Part II of this series, "HDR Best Practices: In Post"
Ok. Now we know what HDR is (Right?). Should this be a call to grab your NRA card and start rifling off brackets of everything that moves (actually, things that move can be an enemy of bracketing but we'll get into that in a minute)? Maybe, but not really. It is important to learn where HDR will truly benefit your shot. We've established that HDR imaging is best used when a scene has a lot of dynamic range. So, right there is a perfect example. Before you fire off a single exposure, look at your scene. Are you in a field at 1PM with the sun directly over you and the light is flat throughout? If so, I don't think HDR will do much for you other than add a ton of noise and haloing to your image.
However, there is another byproduct of HDR processing that could warrant shooting your brackets. That byproduct is an increased display of texture. If you are shooting a scene that may not have a lot of dynamic range but does have elements that you'd like to capture the texture(s) of, then bracket away. I've repeatedly been blown away with the way that HDR handles texture, making it pop off the screen.
To summarize, there are no hard-and-fast rules of when you should or should not shoot your brackets. I've just noticed trends in terms of timing, lighting conditions, and subject matter that has either had a positive or negative impact on my HDR work. So, I suppose what I'm trying to say is YMMV.
Best Practice #3: Be Cognizant of Your Scene
Because you will be grabbing exposure data from multiple brackets, you should be aware that elements in motion will likely cause some sort of ghosting. Depending on what is moving and at what rate, this may be a negligible thing. I've become increasingly keen to paying attention to the rate at which clouds are moving, as well as water and foliage such as leaves and grass. There are certainly ways to minimize or deal with the ghosting during post processing and I'll go into that when I release that section of this HDR Best Practices Guide.
If your scene has a lot of people or cars, it may be a bit harder to mask each of these moving elements out. In these cases, I'll look to see if I can create an HDR from the single best exposure in the bracket series. This will also be something that I'll cover in the Post Processing portion of this Guide.
So you've decided to shoot some brackets with the hope of tone mapping that goodness into an HDR image. Wait? Bracket-what? Brackets are the sequence of images that you take at varying exposures. It's an affectionately used term that I use whenever talking about shooting for HDR images. In order to ensure that the quality of your brackets (not the quality of your composition, that is) are optimal, here are some sub-steps that I follow in the field:
Best Practice #4A: Get Proper White Balance Targets
So we're about to embark on a fantastical journey of bracketing. You've spent the time scouting your scene and are about to set up to shoot. So why not take an extra few moments to shoot a gray target and ensure proper White Balance? While achieving proper White Balance is not exclusive to HDR photography at all, it is a critical part of it. It is of my opinion that improper White Balance compounds itself during post processing. So, save yourself the hassle and grab a WB target shot.
I strongly recommend the X-Rite ColorChecker Passport for your Custom White Balance needs. You also get the added benefit of being able to create a custom DNG Color Profile to ensure consistent color in each of your brackets. I live and die by mine.
Best Practice #4B: Compose Your Shot with a Steady Camera
It goes without saying that the first thing you should do it find a shot that piques your interest and compose it within the frame of your camera. However, if you're planning on shooting several brackets, then you're going to want to make sure that your camera is as still as possible.
If there is one thing that leads to a loss in quality when tone mapping, it is having shifts in movement from image to image. The most common culprit is when your camera is not properly braced. This is why I carry my tripod just about everywhere I go. In fact, next to the camera and lens, it is my most important piece of gear. If you've set your tripod in an area where there is high winds, I would recommend applying a counter weight (my bag usually works great here) to your tripod to weigh it down. Weighting down your tripod will also help during low-light and nighttime scenes when your exposures tend to creep into the multi-minute time frame.
If you are going to be shooting with your camera on a tripod and your lens has some sort of Image Stabilization/Reduction (IS on Canon / VR on Nikon), you will want to turn that setting off. It's a general rule of thumb that you should turn off your Image Stabilization whenever shooting with a tripod but it is more pronounced when shooting several brackets for HDR.
If you find yourself shooting without a tripod, then I recommend trying to set your camera down or brace it, if possible, before shooting. If you are going shoot your brackets hand-held, then I recommend trying to brace yourself against a wall or even the ground.
Best Practice #4C: Set your ISO, Aperture and Focus
Now that your shot is composed and your camera is braced, you'll want to decide the ISO and Aperture that you wish to use and set it. In terms of ISO, I highly recommend using your camera's lowest setting to keep the noise in the frame down to a minimum (I absolutely always have my camera set to ISO100). For Aperture, if you're using your camera's Auto Exposure Bracketing function (more on that in a second), then I would just set the camera to its Aperture Priority mode and select your aperture there. If you're going to manually bracket or use an external device, then I would set the camera to Manual mode.
Now that you've locked in your aperture, you're going to want to find what your point of focus is. Once you achieve your desired focus, make sure that you turn off your lens' Auto Focus. Forgetting to do this will lead to the camera re-attempting focus in between each exposure and this can be detrimental to the overall quality of your brackets. Personally, I utilize my camera's Live View mode and zoom in on the area that I wish to focus on. This works wonders and has yet to fail me, although it does drain the battery at a much quicker rate (so make sure you have spare batteries... and digital media).
Best Practice #4D: Prepare Your Camera to Bracket
Ok, you are ready to fire off your brackets. Solid. Now, you have to prep your camera to fire at different shutter speeds. You can do this several ways:
You can manually adjust the shutter speed on the camera.
You can set your camera to Auto Exposure Bracketing. Most dSLR cameras have this ability, where the camera will automatically adjust the shutter speed against a pre-determined number of brackets based on the mid-range exposure of the spot that the camera is metering off of.
Another alternative is to use the Promote Control by Promote Systems. With this device, you are letting the remote unit issue the shutter speed of each bracket to the camera. This is the solution that I use, love, and recently reviewed.
It's go time. You are finally ready to expose your bracket sequence. But, what is the best way to trip the shutter? Well, you've got a few options. If you've got a Promote Control, then the unit will take care of releasing each exposure. Alternatively, you can use any variety of wired or wireless shutter release remotes. If you find yourself having to actually use the shutter release button on your camera, then I would recommend setting it to a delayed exposure so that the shutter will release after either 2 or 10 seconds (or whatever your camera's timer is set to). The point is, if you've got to all this trouble to ensure that your camera will not move, why introduce movement by pressing the shutter? To that end, if you are exposing in a dark area, you can go the extra step and activate your camera's Mirror Lock-up to even further reduce chance of movement/vibration.
Best Practice #4F: Review Your Brackets
Sweet! You now have a series of brackets that are ready for tone mapping lovin'. Well, how sure are you? When you go to tone map, the information in each bracketed image that you provide will play a huge role in the quality of the image. So, what should you be looking for? Well, you want to make sure that you have captured good detail in every part of your scene.
When I review the brackets on the back of my LCD, I start with the fastest exposure and ensure that I have good detail in the brightest parts of the scene. Usually, this means that I can see everything through a window or doorway (assuming that the scene has a window or doorway). As I skip through to the slower exposures, I'm looking for detail in the shadow areas. Usually, this is under a chair or car or canopy.
If I find that I am missing the desired amount of detail in either the shadow or highlight areas, I will manually adjust the shutter, using the Promote Control, and get the exposure(s) that contain the data.
In the end, if you've been able to follow these steps (suited to your taste, of course), then you should now have a bunch of brackets ready to be tone mapped. And that is a whole other story. Stay tuned for the companion parts to my HDR Best Practices Guide. I'll go into the tips and tricks that I've found work best around Image Management and creating the final HDR product.
Just keep shooting!
Editors Note: Part II of the HDR Best Practices Guide is on the Brian Matiash Blog. As Brian can attest, HDR images look absolutely phenomenal when printed on canvas. To see the stunning canvas print options for your own photography, visit the Artistic Photo Canvas website.