In the relatively short history since the first photograph was taken by Joseph Niepce in 1826 there has been some incredible technological advances in the art form. Color film was invented after the many advancements in the black and white film’s process, but even more significant was the evolution from film capture to digital capture. With the dawn of digital age and advancements in camera and software technologies there came a solution to an age-old photographic problem, capturing all the detail in scenes with very high contrast light (bright highlights and dark shadows) with just one exposure. With the advancement of High Dynamic Range HDR technologies, the high contrast problem was solved.
Let’s keep this simple and break up the discussion into two parts; the problem and the solution!
First the problem; As a photographer when you’re confronted with a high contrast scene using a film and digital camera, no matter how advanced your camera might be, it cannot record light (in one exposure) the way we see the scene with our eyes, especially when the contrast is high.
There are many situations we might experience high contrast in one scene. Below are two common situations with just natural light:
A reasonable question might be, why can’t the camera record light the way our eyes see it?
In order to answer this question, let’s take one step back and define what dynamic range means. Dynamic range describes the relative difference between the darkest and brightest areas of a scene that contain detail.
When we view high contrast with our eyes (without the camera), our pupils adjust to accommodate the differences in contrast between the dark and bright areas. Meaning our pupils expand to see details in the shadows and constrict to see details in highlights. Our eyes have a range of about 18 – 20 stops of light. Because of this fact we can say our eyes have a relatively high dynamic range. When this same scene is recorded on film or captured digitally, it cannot record detail in both the shadows and highlights at the same time with just one exposure. The camera’s sensor has a dynamic range of about 12 – 14 stops of light. With this fact we can say that the camera has a relatively low dynamic range compared to our eyes. Knowing this, we have a choice to make when we are confronted with it, we can create a bright exposure for the shadow details and we lose detail in the highlights or we can create a darker exposure for the highlight details and we lose detail in the shadows, but we can’t get both with one exposure if the contrast id high enough.
If you would like to understand how to read a histogram illustrated in the previous image examples, below is a link to a good short YouTube video that explains it.
Now that we know what the problem is, let’s discuss the solution.
In the digital world we can create two exposure, one for the shadow detail and one for the highlight detail. Once that’s accomplished, we can merge the two individual exposures with High Dynamic Range technology or HDR. We now have two alternatives to manage this; in camera automatically or thru a post-processing application software.
Nearly all digital cameras (even smartphones) these days have the ability to merge exposures to HDR automatically. It’s relatively easy, the results are good and there’s no need for any post processing on the computer! There’s one caveat however, the merged file is converted to jpeg even if you’re capturing a RAW file format. For those of us who want to take full advantage of postprocessing quality of a RAW file quality, jpeg file format isn’t so great!
Note: If we decide to postprocess using HDR software to merge the RAW files, capturing the information(details) in both shadow and highlight is critical. We can approach the exposure settings in a few ways.
- We can use the histogram in the camera to make sure you have captured all the details in both shadow and highlight in two separate exposures.
- We could use your camera’s spot meter and manual exposure mode to ensure there is detail in the shadow for one exposure and detail in the highlight in the second exposure by using this metering method. A good starting point is to expose the shadows at -1.5 and highlights at +1.5.
- We could also use the auto exposure bracket (AEB) function in the camera to capture the files you need. You’ll find the AEB function in the “shooting menu” in most camera brands.
A really important thing to keep in mind, no matter what approach you decide to use, is to “make sure” you capture all the shadow and highlight detail in the exposures. You’ll regret it later if you don’t.
A couple other things to consider when creating the files, it is highly recommended to use shutter speed to change the exposure between shots. Aperture can modify sharpness caused by changes in depth of field and a change in ISO just add noise.
Some also people ask if a tripod is required when capturing the exposures. It helps with alignment when the software merges the files, but it’s not absolutely necessary. Most HDR programs have the ability to align the images when they merge, but some cropping will be required if the alignment isn’t perfect, which it never is if you’re hand holding the camera.
Once you captured the two exposures, you’re ready to merge the files on the computer with your HDR application. This is the easy part, because the software does most of the heavy lifting!
*Note: There are many HDR applications on the market like; Photomatix Pro, Nik HDR Efex and HDR Merge just to name a few, but other applications you might already use, like ON1, Photoshop and Lightroom Classic, HDR functionality is built in! How convenient!
Merging HDR Photos in Lightroom Classic
I use Lightroom to merge files to HDR. Here’s the workflow.
In Lightroom Classic:
- Select the files to be merged
- In the LR Menu Bar go to Photo, then Photo Merge, then HDR
- Select Auto Align, Auto Settings and a Deghosting level
- Click on Merge
If you are capturing a scene where something has moved (cloud or foliage movement and even people) within the frame between exposures, most HDR applications have a ghosting feature that removes the ghosting that would be obvious after the merge. In Lightroom Classic for example and Photoshop, Merge to HDR allows you to choose a selection (None, Low, Medium and High) based on how much ghosting is perceived by Lightroom. An overlay can be viewed to show where that ghosting was recognized.
After the software has completed the merge, you may have to do some minor adjustments to color saturation and exposure adjustments to the shadow and highlights to match what you were seeing in the field. All the flexibility is there because all the information is present! How awesome is that.
Historically, one of the biggest road blocks for photographers when confronted with high contrast was the ability to create images that match the way our eyes see the world. No more, HDR technology has allowed us to overcome that road block and happy photographers are rejoicing everywhere. You will too!
Happy merging everyone,
Doug Johnson (Doug Johnson Photography Workshops)
Need help finding great light for photography? Check out this article!