Exposure blending is a revolutionary digital darkroom technique that will assist you in overcoming the limitations of your camera and capture a scene with the full tonal range you witnessed in the field. This is a common challenge for any area of photography, but landscape photographers find this especially difficult since we typically can not manipulate or alter the ambient light.
You’ve probably recognized this challenge in your own work: an overexposed sky, a foreground with crushed shadows, or a disappointing combination of the two. The incredible detail and light you witnessed in person has disappeared, and you instead go home with a lackluster representation of the beauty you intended to capture.
Since your camera sensor (the digital equivalent to a negative) is limited to one aperture and one shutter speed across the same frame, it’s difficult to capture a scene with a dynamic tonal range without some areas falling outside of your selected exposure, which produce blown highlights and/or crushed shadows.
By autobracketing your landscape and blending exposures in Adobe® Photoshop, you can recover this lost data for a more accurate and complete rendering of the scene you intended to capture – like in the example below.
How Autobracketing Works
Simply put, in order to capture the full tonal range of a scene that extends outside of what your sensor can render, you’ll need to combine different exposures together. The number of exposures you need depends on how large your tonal range is, but typically you’ll have one exposure metered for your highlights (a faster shutter speed to limit light), one for your shadows (a slower shutter speed to let more light in), and one as your base exposure (the average metering between your highlights and shadows).
This is where the term “bracketing” comes in since you’re creating a bracket that encapsulates your entire tonal range, from brightest to darkest.
Exposure blending can also be referred to as HDR blending in the sense that we’re expanding the tonal range, however this method will create a more natural looking image than tone-mapping with automated software.
With exposure blending, you have much more control over the end result by manually choosing exactly where you want to blend your exposures together, and at what strength you want that blend to be. It’s a method that is entirely customizable to your scene, which will produce a more pleasing result.
The group of brackets above shows how you can take three different exposures of the same scene and combine the best details of each one to create one final image that has no loss of data for a complete tonal range.
By using a combination of written instructions and video screenshots, I’ll teach you how to autobracket your scene and achieve a seamless blend of exposures so you can fully enjoy your photography by overcoming your camera limitations.
The need to bracket a scene in order to capture the entire tonal range is quite common, which is why camera manufacturers have made it easy to photograph the same subject at different exposures. “Autobracketing” is a fantastic feature available on most DSLRs, which allows you to take multiple exposures automatically without having to change your shutter speed manually.
When you set your camera to autobracket, it takes three (sometimes more) sequential images at different shutter speeds, usually 2 full stops apart. This helps to streamline your workflow when presented with a wide tonal range that one exposure can not contain.
The amount of stops between each exposure can be adjusted depending on your scene, and for most situations three different exposure values (EV) capturing a four stop range will be sufficient: your base exposure (EV +/-0), an exposure to recover blown highlights (EV -2), and another to recover any crushed shadows (EV +2).
What is Raw Format?
Your exposure blending capabilities depend greatly on the quality of your brackets; a basic image format will give you basic results. However, the more data you have to work with, the easier it will be to blend multiple exposures together.
This is especially important for expansive tonal ranges which require a more intricate blending workflow. In other words, the best exposure blend begins with the strongest foundation to build your image upon, and that foundation is raw format.
A raw file is the digital equivalent of a film negative before it is printed onto paper; it’s the “raw” state of your image that you can’t really use as a photo, but all the information you need to create a photo is there. You can’t upload a raw file to your website or email it to others without special viewing software, but you can take that raw file and turn it into a universal format (such as TIFF or JPG) once you have finished with your processing.
There are many specific benefits of raw format over JPG, but it all comes down to a higher-quality image as you are working in the pure, uncompressed state of your photograph, which is essential for exposure blending.
The Advantages of Raw Format and Bit Depth
Raw format is notable for its enormous color depth (also known as bit depth) when compared to the more universal JPG.
With a raw image, you are working with a minimum of 12-bits, which translates to 4,096 tones for each of the three color channels (red, green, and blue). However, JPG is limited to 8-bits, which gives you only 256 tones for each channel. Technically, raw format is immensely superior to JPG as there is much more data contained for each color channel.
While 4,096 tones for each channel may seem excessive, consider this: the more data you have to work with, the easier it is to maintain color integrity. When blending different exposures together, this becomes extremely important as you may need to call on that extra data to recover your crushed shadows and blown highlights (explained later).
If you have the ability to use a more sophisticated format, it makes sense to use it as exposure blending is entirely dependent on recovering as much detail as possible.
For the purpose of exposure blending, this additional data gives you an enormous advantage over JPG when adjusting your exposure, and will also reduce processing artifacts (such as pixelation and/or posterization) later on if you decide to process your image further after blending.
Here you can see how the expanded color depth of raw can benefit your photography.
This sunset image was originally overexposed for the sky, and as a result important cloud detail was lost to
blown highlights. To reverse this, I would need to reduce my exposure and bring back that lost sky interest.
When I work in JPG mode and reduce the exposure by two full stops (top), not much detail has been recovered since an 8-bit file has a very limited range to work with.
However, when I use a raw file of the same exact photograph (bottom), which is uncompressed, you can see how much more detail is recovered when I adjust the exposure down by two full stops.
Raw Adjustments vs. Autobracketing
With raw being such a versatile format, why is there a need to autobracket when you can create multiple exposures straight from one raw file?
It would save time spent on setting up a tripod, taking three (or more) images, and also save on disk space. Isn’t raw a magical exposure recovery tool?
It’s always best to capture the optimal exposure for a scene in-camera simply because you’ll have more data in a correctly exposed image than one that has been adjusted artificially, even if it’s in raw format. The more data that is rendered onto your sensor, the more detail your image will have. Raw has its limitations; it does not give you the power to shoot blindly with no regard to proper exposure.
One substantial benefit to bracketing a scene vs. adjusting a raw file is that the exposure recovery power of raw format is typically limited to +/- two full stops before the quality begins to deteriorate. Depending on the tonal range of your scene, you may need 3 stops, 5 stops, or even more between your longest and shortest bracket in order to recover all of the detail.
Recovery limits aside, capturing an exposure that has been adjusted in-camera vs. adjusting a raw file by the same number of stops will always give you the higher quality photograph.
The recovery capabilities of RAW format should not be a replacement for bracketing a scene, and here we can see why.
The top image is the same example used in the previous image: a raw file that has been reduced by two full stops in processing. The bottom frame is the same exact scene, but is a bracket that was captured two stops less in-camera, so no exposure adjustment was needed in process. When you compare the cloud detail between each example, you can see how much more data was recovered by bracketing.
This comparison shows that instead of trying to recover missing detail in processing, you’ll obtain a better result if you adjust your exposure in the field.
Why Autobracket in Raw Format?
If it’s better to adjust your exposure in-camera rather than as a raw file, why even bother with raw at all and instead autobracket in JPG?
Although raw format can not replace autobracketing, it’s still a file format that has many benefits over
JPG and should be used when you bracket. Not only is there more data in raw format, but you’ll greatly increase your tonal range for editing.
If you autobracket in JPG format, you’ll typically be taking three images: your base image, one taken two stops faster, and another two stops slower, for a total range of four stops. However, if you shoot in RAW format, you can increase or decrease your brackets by two stops in process. That safety net will add another two full stops to your range on both ends of your bracket, bringing your total tonal range up to eight stops (assuming you capture three brackets in two-stop increments).
Blending exposures using one raw file is best for those candid shots where you didn’t have enough time to set up a tripod but need to correct some blown highlights, or simply want to brighten/ darken parts of your image – like in wedding or action photography.
It’s a fantastic way to save an otherwise unusable photo, but if you have the time and ability to autobracket your landscape for exposure blending, this is the method which will give you the highest quality output with the largest tonal range.
Exposure blending and bracketing is not just for combining bright skies with dark foregrounds; you can use it in many different ways as part of a non-destructive workflow.
You can recover blown highlights in water reflections, bring back detail lost to the shadow of a tree, or to blend a brighter foreground with a darker background (like under stormy, overcast skies).
Another popular use of this technique is to blend different long exposures together – for example, blending an extended exposure that captures moving clouds with an image that shows stationary grass that would otherwise be windswept if taken at the same shutter speed as the sky.
Now that you know why we autobracket for exposure blending, it’s time to go over the in-camera workflow; the process I go through to capture those bracketed images to later blend in process.