What is HDR?
HDR stands for High Dynamic Range. Dynamic range is a measure of the range of different light levels, from the darkest black to the brightest white, that can be recorded or displayed by a device. It defines the amount of contrast you can capture without losing detail at the extremes. A good example of this would be something shot against a bright sky or landscape featuring direct sunlight and shaded areas. Normally you can expose for the bright areas, and lose detail in the shadows, or vice versa.
HDR combines multiple exposures which capture a frame for highlights, midtones and shadows. These are then merged to form one image preserving the details of the shadows and highlights.
There are other methods you can use to get the perfect exposure - using the flash or an ND filter - for example. The HDR technique is, however, the easiest.
HDR images can be captured on any camera, although some cameras (and smartphones) have the ability built in. In all cases, they typically take 3 exposures (frames) in quick succession and merge them leaving you with one HDR photo. Some cameras have different preset effects for HDR such as vivid, bold and embossed.
If your camera does not have an HDR feature don't fret. This guide will show you how to achieve this effect with a little bit of manual effort.
How to take HDR Frames?
Essentially, the process is the same as that used for exposure bracketing. In fact, you can use the bracketing feature if you have it to aid in capturing the frames. Use the auto-exposure bracketing set to around 1 stops either side. This is a starting point, you may have to increase the number of stops depending on the scene brightness.
Because we are taking multiple shots one after the other, these techniques can only be used on stationary subjects. Even a breeze in the trees can create ghosting which can spoil the effect.
The basic principle is to set the lens focus manually, use a tripod, and set the exposure to aperture priority so the depth of field remains constant. Set the camera to the fastest continuous drive setting available and take around 3 photos using exposure bracketing. We then use software to stack these images into one HDR photo.
HDR Photography Step by Step
Shooting HDR photography is not as complicated as it sounds. All you need to do is take a sequence of images by bracketing at different exposures, from underexposed to overexposed. How many images you need and what the difference in exposure between shots should largely depend on what you're photographing.
Here's how to make a high dynamic range image.
Step 1 - Keep it Steady
As you'll be combining multiple shots to make your final image, the composition needs to be exactly the same in each photo. This means a sturdy tripod is vital. You'll also need to take steps to avoid any camera movement between shots, so use a cable release so you don't have to touch the camera at all during the process.
Step 2 - Camera Settings
Your aperture has to remain constant throughout the sequence, otherwise, the depth of field will change between shots and this will make aligning them more of a challenge. So, switch to your digital camera's A, or aperture-priority mode. Now the camera will vary the exposure by changing only the shutter speed. We used an aperture of f/11.
In most cases, three to five images with a one- or two-stop difference between one shot and the next is enough for constructing an HDR image, but if the scene has a very wide brightness range you may need to shoot five or seven frames. Most HDR software can process NEF files, so set image quality to raw format for the best results.
Now set your camera to the continuous shooting mode. If you have a choice of speeds, pick the fastest available. This will minimise any cloud and tree movement between each shot which can cause nasty 'ghosting'. You'll now be able to take all the shots you need for the HDR sequence without touching the camera.
Step 3 - Auto Bracket
Activate your camera's auto-bracket feature. This will calculate and adjust the exposures in your sequence. There are two settings. One is the number of shots - three is the normal number, but some cameras let you shoot five. The second setting is the interval between the shots. This can be 1EV, 2EV or, on some cameras, 3EV.
Take some test shots before starting. The longest exposure should show detail in the darkest areas, such as the shadows, while the shortest exposure should show detail in the brightest ones, such as the sky. Use the histogram to assess exposure.
Step 4 - Blend your shots
Once you have a set of exposures you need to blend or merge, them using image editing software. Adobe Lightroom has a very good, and easy, HDR merge tool. Other software applications perform the same effect in a similar process.
From Lightroom, Select Photo > Photo Merge > HDR. In the HDR Merge Preview dialogue, deselect the Auto Align and Auto Tone options, if necessary. You can preview the effect of these settings right within the dialogue box. Click Merge to create the HDR image. More instructions are on the Adobe website.