Part 2 - Capturing and Processing HDR Images
Correct bracketing is the key to creating a good HDR image
Part 1 - Shooting for High Dynamic Range Images
Welcome to Part 2 of this two-part series, HDR: From Capture To Post, here on the Canon Digital Learning Center. In Part I we began our exploration of HDR photography, explaining what it is, and showing how you can begin to expand the range of tones in a RAW image simply through techniques in RAW processing software. In Part 2, we'll talk about taking things further: First, about using true HDR processing software. Then, we'll discuss taking multiple original images of the same scene taken at different exposure settings in order to really expand the visible dynamic range in our final images.
For those who are brand new to HDR, here's a suggested workflow.
- After taking the RAW original images for your HDR sequence, use a card reader to get files into the computer or a folder in a connected hard drive. It's faster than connecting the camera directly to the computer.
- Put each HDR sequence in a folder, and name that folder so you can easily find it. Make sure you have the right set of images in that folder. That's important because when shooting multiple sets of HDR images, it's sometimes possible to pick a wrong image, or two.
- Open an HDR software program. Two popular applications are Photomatix and HDR Efex Pro. These aren't the only two HDR software programs available – so if you prefer another program, by all means learn it and use it.
Select your RAW files and follow the on-screen prompts, and then follow your preferences when it comes to selecting HDR effects.
Photomatix or HDR Efex Pro can take original RAW image files from popular digital SLRs (.CR2 files if you shoot with a Canon EOS camera), and process them plus perform their HDR magic. If Photomatix or HDR Efex Pro can't recognize your RAW files, it's usually because you don't have the latest version of the HDR program (always check for updates), or because the HDR program has not been updated (see links later in this article). Sometimes, when new cameras are introduced, it takes a while for the software to be updated. If that's the case, you can use a conventional RAW processing program, like Canon's Digital Photo Professional (DPP) software, to convert your RAW files to TIFFs, and then process them with the HDR program. In fact, some photographers convert the RAW files into finished JPEGs, and process those files into a finished HDR image - with good results. Once you have your processed HDR images, back them up somewhere. You should always back up. Always.
Making HDR Images
The first picture in the gallery, taken in Nelson, Nevada, was seen in Part I of this HDR series. It's an example of when taking multiple exposures (bracketing) and using a true HDR program was needed to create an HDR image that shows both shadow and highlight detail. The contrast range was just too great to be brought out with a single RAW image and RAW processing techniques alone.
Correct bracketing is the key to creating a good HDR image. You need to take enough images to capture the entire brightness range of the scene. Sometimes setting your camera on automatic exposure bracketing (AEB) and setting your bracketing range to 0, +2 EV and -2 EV will do the trick – if the contrast range is not greater than about four stops. The photograph of the Buddhist temple in Part I is an example of AEB set at to 0, +2 EV and -2 EV.
However, when the contrast range is greater than about four stops, and when there are very dark and very light areas in the same scene, you'll need to do the following:
- Set your camera on Manual exposure control
- Set the aperture
- Bracket by changing the shutter speed (never change the aperture in an HDR bracketing sequence because it changes the depth-of-field which should be consistent throughout the entire sequence)
Here is a basis bracketing technique:
- Start at 0 EV (normal, camera-determined exposure)
- Take exposures at +2 and -2 EV
- After taking those three exposures, bracket your exposures in one f/stop increments - over and/or under the +2 and/or -2 EV setting accordingly
A screen grab from the Adobe Bridge window shows the five original images for the opening image. The exposures (clockwise from top right) were: 0, +2, -2, -3 and -4 EV. Bracketing was done manually. (Important: more shots that were progressively under-exposed were required for this shot... taking more exposures in the opposite direction - in the + EV direction is sometimes necessary as well.)
The blinking Highlight Alert you can activate for playback on your camera's LCD monitor can be a big help here. Take one or more exposures under the 0 EV setting, until nothing of importance in the scene plays back blinking. Then, as equally important, take "overexposed" images to capture detail in the shadow areas of a scene. Most of today's digital SLRs don't have an on-screen warning to show areas that are too dark. Shoot images that are progressively lighter in exposure, until some detail in the darkest areas of the scene appears when played-back on the back of the camera.
Obviously, the 0 EV shot shows the scene outside the windows extremely overexposed. Additional exposures at -2, -3 and -4 were needed to capture the detail in the outdoors scene. However, only one exposure at the +2 EV setting was needed to capture the detail in the shadow areas of the scene.
Canon EF 17–40mm f/4L lens
An example of the EF 17–40mm f/4L wide zoom lens field of view.
Adobe Bridge Window
A screen grab from the Adobe Bridge window shows the five original images for the opening image. The exposures (clockwise from top right) were: 0, +2, -2, -3 and -4 EV.
Shot at 0 EV
The 0 EV shot shows the scene outside the windows extremely overexposed.
This set of images was processed in HDRsoft's Photomatix Pro, but you would get basically the same results in other HDR programs. Processing HDR images is an art, and learning HDR programs requires more space than we have here. Check out the various software and editing tutorials, such as those on both the HDRsoft site and Nik Software site.
This screen grab of the Tone Mapping window in Photomatix Pro shows the two most important setting are the Black Point and the White point sliders. Start by moving the sliders all the way to the left. Move White Point slider to the right until you start to lose details in the highlights, and then move it back to the left. Do the same with the Back Point slider until you start to block up the shadow areas. If you lose highlights and block up the shadows, you miss the point of creating a true HDR image. Many professional photographers feel these are most important settings for HDR programs.
This screen grab of the HDR Efex Pro processing window shows the most important control is the Tone Compression setting. It's here where the degree of HDR effect is controlled.
While we are on the topic of processing, and before we get back to shooting, let's take a look at enhancing HDR images in Canon Digital Photo Professional (the software that is included with your Canon digital SLR). The screen shot show just some of the controls, along with the finished HDR image, after it's been worked-on in an HDR program.
HDR images often tend to look a bit soft. To sharpen them, if you've saved them as JPEG or TIFF images with your HDR software, open them in Canon Digital Photo Processional and boost the Sharpness and Contrast, making sure not to boost the contrast too much as to block up important shadow areas of a scene. For the old barn picture, the saturation was boosted to add some warmth to the image.
Photomatix Pro Tone Mapping Window
This screen grab of the Tone Mapping window in Photomatix Pro shows the two most important setting are the Black Point and the White point sliders.
HDR Efex Pro Processing Window
This screen grab of the HDR Efex Pro processing window shows the most important control is the Tone Compression setting. It’s here where the degree of HDR effect is controlled.
The screen shot show just some of the controls, along with the finished HDR image, after it's been worked-on in an HDR program.
Okay, back to HDR image capture as promised. Now, let's take a look at when you need to take more exposures over the 0 EV setting.
This image illustrates the benefits of HDR: Here, in the finished HDR image, you can see details in the scene outside the car, as well as on the floorboards. This shot was created from a series of images taken with the 15mm fisheye lens. The camera was placed on a lightweight tripod that was set up on the floor in the backseat of the car.
Here, a screen grab from Adobe Bridge shows six exposures needed to capture the entire dynamic range of the scene. Clockwise, from top right: 0 EV, -2 EV, +2 EV, +3 EV, +4 EV and +5 EV. Here, an exposure at -2 EV was enough to capture the details outside the car. However, as you can see, overexposing the scene was necessary until all the details, including the spider web on the floorboards, were visible.
One question that is often asked is whether it would be easier to take the same number of exposures over and under the 0 EV setting and save the hassle of bracketing more in one direction than the other. The answer is this: Chromatic aberrations creep into HDR images – the more images, the stronger the chromatic aberrations. Secondly, more images require more processing time, which can add up when the HDR software is processing your RAW files.
Here is a quick tip for determining the number of exposures you need for an HDR sequence: use the sun or main light source to help you. If you are shooting toward the sun/light source, you'll need fewer exposures than if the sun/light source is off to your side. If you are shooting away from the sun/light source, you may not even need HDR, because with even, front-lighting, you can pull out so much detail from the files in today's digital SLRs.
This image was taken in Monument Valley. Notice the shadows and highlight in the image. They add drama and create a nice mood in the photograph.
Here is the HDR version of the same scene. Sure, the highlights are maintained and the shadows are opened up, but the intense mood of the scene has completely changed.
Keep in mind that the most important element in any photograph is the mood or feeling of the image. Lots of detail in the dark shadow areas or bright highlight areas is great – but only if it really contributes to the finished photograph you're trying to create.
There is a time and a place for HDR. Sometimes, the play of light and shadow in natural lighting is what attracted you to the scene in the first place, and there's no need for digital techniques to alter it.
This two-part series began with a mention of Ansel Adams and his black-and-white images. Well, after you create your HDR images in a true HDR programs, try creating beautiful HDR images from a single original RAW file in Canon Digital Photo Professional, by reducing the saturation and experimenting with the contrast and curve controls. I think you'll like the results, especially on your landscape HDR images.
There is much more to discover about HDR image capture and processing. This two-part article will get you started with the most important information to create great HDR images.
This shot was created from a series of images taken with the 15mm fisheye lens. The camera was placed on a lightweight tripod that was set up on the floor in the back seat of the car.
A screen grab from Adobe Bridge shows six exposures needed to capture the entire dynamic range of the scene. Clockwise, from top right: 0 EV, -2 EV, +2 EV, +3 EV, +4 EV and +5 EV.
Notice the shadows and highlight in the image. They add drama and create a nice mood in the photograph.
Monument Valley: HDR Version
The HDR version of this scene has completely changed the intense mood of the scene .
Black and White HDR
Experiment with reducing saturation and utilize contrast and curve controls for landscape black and white HDR images.
The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.
All images are copyright Rick Sammon