Politics, Religion, Economics, HDR. There seems to be little in the photographic world that starts such heated discussions as the concept of HDR photography and processing. Truth of the matter is, it is a very popular technique and can be done with a multitude of results, some more visually shocking than others, but I believe HDR gets a bad rap too often. Let me start off by saying, I am not an HDR expert. I do not feel that my techniques are an end all by any means, but I have figured out some very helpful techniques that I feel can benefit those looking to get into, or better understand capturing and processing HDR imagery. For me, capturing the dynamic range of a scene is the primary concern while the way these bracketed images are processed is an entirely personal decision. Too often, I see people tonemapping single images, or running them through an HDR-like software to give it that grungy, gritty look and calling it “HDR.” While many of those images have a very cool look to them in their own right, it still doesn’t quite qualify as a high dynamic range photo by definition in many cases. C’mon in and we can discuss ways to capture the whole dynamic range of any particular scene along with some tips and tricks.
Dynamic range in an image or scene, is the measurement between the brightest bright and darkest dark in regards to luminance translated into photographic stops. The dynamic range that humans are capable of viewing is many times greater than what current film and digital sensors are capable of reproducing in a single image file. Herein lies the idea behind capturing and processing a greater dynamic range into a single image to produce a wider range of luminance value closer to what we are capable of seeing. HDR (High Dynamic Range) imagery is the capture and processing of multiple exposures made at differing exposure values to attempt to blend properly exposed highlights, shadows and everything in between. Many software programs have been developed recently that combine these bracketed exposures by way of local tone mapping, which is a method of blending the range of tonality and luminance from multiple exposures into a singular file. This can produce a vast spectrum of results based on which software you use, or how you adjust the image within the software.
I have been intending to write a short series on HDR having spent the last year trying to fine tune my technique in both capture and processing, so this will be part 1. I’m sure there are many other photographers out there with differing techniques, but these two have worked for me and are good starting points from which to gather the info to process into an HDR image.
Let’s make a quick note about the actual dynamic range capable of being reproduced on a computer screen and in print. Most all computer screens, printers and photographic papers are incapable of displaying or reproducing the dynamic range and digital bit depth that any high contrast scene may actually present in true/real world luminance as the eye sees it. That said, it shouldn’t stop us from using more info in an image file, so let’s get to it.
I’ve used two separate capture techniques at different times as well as a variety of different processing techniques when wanting to extend the dynamic range of any given image or scene. We’ll start with capturing a wide dynamic range and move into processing in the next post.
For this technique, it will be handy to know how to shoot in Manual (for an article on how to shoot in Manual, click HERE), as well as being able to switch, and understand your metering mode (for an article on Metering, click HERE).
Capturing Dynamic Range.
There are two basic ways to capture bracketed exposures, AEB (auto exposure bracketing) and Manually, but to truly determine the dynamic range of a scene, I feel it beneficial to put the work in as depending on the actual dynamic range, there may only be one way to truly capture all the necessary values, but on the other side of the coin, conditions may limit the capture techniqe.
Establishing and Capturing Dynamic Range Manually:
First, establishing the dynamic range of a given scene;
- Set your camera up to Aperture Priority (A, Ap, Av, etc) and set your working aperture. It entirely depends on what you’re shooting, and how you want to work with your depth of field in the scene, but for the sake of our exercise, let’s set our aperture to f/8. The reason we use Aperture Priority is because when we are bracketing our exposures, we want to make sure our DOF and point of focus stays consistent.
- To determine the Dynamic Range, I find the best way to do so is to set my camera up to SPOT METER. If you’re unaware of how to do this, read the metering link above, do a quick google search on your camera, or pull out the manual and look for the “Metering” section. Spot metering is essentially recording proper exposure (unadjusted at “midtone” by default) for whatever light is falling on/reflecting off of whatever you are metering in a very small point on the sensor which enables you to pinpoint exposure values in the scene. What we are wanting to do here is use our spot meter on the brightest and darkest part of the scene which we are wanting to capture detail in.
- Find the brightest area in the scene, spot meter so that your light meter reads the highlighted area as the midtone (right in the middle of the light meter) and write down/remember the shutter speed that it lists to achieve that exposure. (if your shutter speed cannot get fast enough, adjust your aperture to a smaller setting/higher f number). Don’t take a picture yet…
- After recording the shutter speed for the brightest bright, do the same for the darkest area in the scene sticking with whichever aperture setting you used to record the highlight exposure value. We will call these our “bookend” exposures, so remember the two shutter speed settings from these two steps.
- Firstly, for the best results, use a tripod. I’d also suggest to employ your camera’s mirror lockup feature as well as switching the drive mode to self timer so that you minimize any camera shake.
- Establish your focus and make sure to turn off Auto Focusing.
- On the tripod, frame your scene and switch to “M” (manual) mode on your camera’s mode dial. Set it to the aperture you used to determine the highlight and shadow exposures in the steps above. Now, set to one of your “bookend” exposure shutter speeds.
- We will adjust our shutter speed by one full stop with each shot until we reach our other “bookend” exposure, so after the first shot, adjust your shutter speed by one stop in the direction (either slower or faster depending on which bookend you started with) toward your second “bookend” exposure ending at that second bookend exposure.
- Make sure you’re set to Aperture priority (or Manual) and have your drive mode set to continuous.
- Establish your focus and make sure to turn off Auto Focusing.
- If using the spot metering method, find something in your scene that you want to establish as your midtone. On Aperture priority (or Manual), set your spot meter on that midtone, and use your Exposure Lock to set that to your “O” exposure.
- With your midtone determined, frame your scene and set the camera up on your tripod.
- With our AEB set and our exposure locked, fire away. On continuous drive mode, you should be able to capture at least 3 frames per second or so which will minimize any movement in a scene.