So what if you are doing everything right in terms of metering and mode selection, yet your images still sometimes come out too light or too dark? There is a technique called bracketing that will help you find the best exposure value for your scene by taking a normal exposure as well as one that is over- and underexposed. Having these differing exposure values will most often present you with one frame that just looks better than the others. If I am in a tricky situation when I have to get the exposure right, such as an outdoor wedding, then I’ll use bracketing. I’ll start by spacing my exposures apart by one to two stops and taking three images: one normal exposure, one underexposure, and one overexposure. (Figure 11.7).
As you are viewing the control panel and holding the exposure button, you can decide how much variation you want between bracketed exposures. You can choose from one-third of a stop all the way to two full stops of exposure difference between each bracketed exposure. If I am in a particularly difficult setting, I will typically bracket in two-stop increments to help zero in on that perfect exposure, and then just delete the ones that didn’t make the grade (Figures 11.8–11.10). Remember, your lighting will dictate how many stops you want between exposures.
Setting auto-exposure bracketing
You can quickly set your bracketing by holding the BKT button (on the front of your camera directly below the flash button) while rotating the Command dial to 3F (three exposures).
Next, continue holding your BKT button down while rotating your Sub-command dial to the 2.0 setting (two stops between each exposure). For more information on bracketing, please review pages 109–110 of your manual.
If you are in Single Frame shooting mode, you will have to press the shutter three times, one for each exposure. If you are in continuous shooting mode, you will press and hold the shutter button and the camera will take all three exposures with one press of the button.
When I am out shooting in the RAW file format, I typically shoot with my camera set to an exposure compensation of –1/3 stop to protect my highlights. If I am dealing with a subject that has a lot of different tonal ranges from bright to dark, I will often bracket by one stop over and under my already compensated exposure. That means I will have exposures of –1 1/3, –1/3, and +2/3.
Another thing to remember is that auto exposure bracketing will use the current mode for making exposure changes. This means that if you are in Aperture Priority mode, the camera will make adjustments to your shutter speed. Likewise, if you are in Shutter Priority, the changes will be made to your aperture value. This is important to keep in mind since it could affect certain aspects of your image such as depth of field or camera shake. You also need to know that AE bracketing will remain in effect until you set it back to zero, even if you turn the camera off and then on again.
This section comes with a warning attached. All of the techniques and topics up to this point have been centered on your camera. The following two sections, covering panoramas and high dynamic range (HDR) images, require you to use image-processing software to complete the photograph. They are, however, important enough that you should know how to shoot for success should you choose to explore these two popular techniques.
I’ve never been much for panoramas until I visited the Grand Teton National Park. The Tetons are probably one of my favorite mountain ranges and easily identifiable, but a single frame just doesn’t do them justice. Only a panorama can truly capture a mountain range, cityscape, or any extremely wide vista.
The multiple-image panorama
To shoot a true panorama, you need to use either a special panorama camera that shoots a very wide frame or the following method, which requires the combining of multiple frames.
The multiple-image pano, as photographers often call a panoramic, has gained in popularity in the past few years; this is principally due to advances in image-processing software. Many software options are available now that will take multiple images, align them, and then “stitch” them into a single panoramic image. The real key to shooting a multiple-image pano is to overlap your shots by about 30 percent from one frame to the next (Figures 7.19 and 7.20). It is possible to handhold the camera while capturing your images, but the best method for capturing great panoramic images is to use a tripod.
Now that you have your series of overlapping images, you can import them into your image-processing software to stitch them together and create a single panoramic image.
Sorting your shots for the multi-image panorama
If you shoot more than one series of shots for your panoramas, it can sometimes be difficult to know when one series of images ends and the other begins. Here is a quick tip for separating your images.
Set up your camera using the steps listed here. Now, before you take your first good exposure in the series, hold up one finger in front of the camera and take a shot. Move your hand away and begin taking your overlapping images. When you have taken your last shot, hold two fingers in front of the camera and take another shot.
Now, when you go to review your images, use the series of shots that falls between the frames with one and two fingers in them. Then just repeat the process for your next panorama series.
Shooting properly for a multiple-image panorama
Mount your camera on your tripod and make sure it is level.
In Aperture Priority mode, use a very small aperture for the greatest depth of field. Take a meter reading of a bright part of the scene, and make note of it.
Now change your camera to Manual mode (M), and dial in the aperture and shutter speed that you obtained in the previous step.
Set your lens to manual focus, and then focus it for the area of interest using the HFD method of finding a point one-third of the way into the scene. (If you use the autofocus, you risk getting different points of focus from image to image, which will make the image stitching more difficult for the software.)
While carefully panning your camera, shoot your images to cover the entire area of the scene from one end to the other, leaving a 30 percent overlap from one frame to the next. The final step would involve using your favorite imaging software to take all of the photographs and combine them into a single panoramic image.
Shooting high dynamic range (HDR) images
High dynamic range (HDR) can create stunning images by using the full tonal range of an image. Depending upon your preference they can look quite real or very surreal. I have found people either love or hate HDR, but regardless of what side of the fence you are on it is a wonderful way to understand the effects of exposure on an image.
HDR is used quite often in landscape, cityscape, and, believe it or not, interior design images. Typically, when you photograph a scene that has a wide range of tones from shadows to highlights, you have to make a decision regarding which tonal values you are going to emphasize, and then adjust your exposure accordingly. This is because your camera has a limited dynamic range, at least as compared to the human eye. HDR photography allows you to capture multiple exposures for the highlights, shadows, and midtones, and then combine them into a single image using software (Figure 7.21).
A number of software applications allow you to combine the images and then perform a process called “tonemapping,” whereby the complete range of exposures is represented in a single image. I will not be covering the software applications, but I will explore the process of shooting a scene to help you render properly captured images for the HDR process. Note that using a tripod is absolutely necessary for this technique, since you need to have perfect alignment of the images when they are combined.
Setting up for shooting an HDR image
Set your ISO to 100–200 to ensure clean, noise-free images.
Set your program mode to Aperture Priority. During the shooting process, you will be taking three shots of the same scene, creating an overexposed image, an underexposed image, and a normal exposure. Since the camera is going to be adjusting the exposure, you want it to make changes to the shutter speed, not the aperture, so that your depth of field is consistent.
Set your camera file format to RAW. This is extremely important because the RAW format contains a much larger range of exposure values than a JPEG file, and the HDR software needs this information.
Change your shooting mode to continuous. This will allow you to capture your exposures quickly. Even though you will be using a tripod, there is always a chance that something within your scene will be moving (like clouds or leaves). Shooting in the continuous mode minimizes any subject movement between frames.
Adjust the Auto Bracketing (BKT) mode to shoot three exposures in two-stop increments. To do this, you will first need to press the BKT button while moving the Command dial to the right.
Now use the Sub-command dial to adjust the bracketing to 2.0.
Focus the camera using the manual focus method discussed earlier in the chapter, compose your shot, secure the tripod, and hold down the shutter button until the camera has fired three consecutive times. The result will be one normal exposure, as well as one under- and one overexposed image.
A software program such as Adobe Photoshop, Photomatix Pro, or my favorite, Nik Software’s HDR Efex Pro, can now process your exposure-bracketed images into a single HDR file. Remember to turn the BKT function back to Off when you are done or the camera will continue to shoot bracketed images.
Bracketing your exposures
In HDR, bracketing is the process of capturing a series of exposures at different stop intervals. You can bracket your exposures even if you aren’t going to be using HDR. Sometimes this is helpful when you have a tricky lighting situation and you want to ensure that you have just the right exposure to capture the look you’re after. In HDR, you bracket to the plus and minus side of a “normal” exposure, but you can also bracket all of your exposures to the over or under side of normal. It all depends on what you are after. If you aren’t sure whether you are getting enough shadow detail, you can bracket a little toward the overexposed side. The same is true for highlights. You can bracket in increments as small as a third of a stop. This means that you can capture several images with very subtle exposure variances and then decide later which one is best. If you want to bracket just to one side of a normal exposure, set your exposure compensation to +1 or –1, whichever way you need, and the use the bracketing feature to automatically bracket your exposures.