The following is an excerpt from our HDR Tutorial by SLR Lounge. This workshop dubbed “the gold standard of HDR education” by FStoppers contains over 13 hours of tutorials, RAW files for you to follow along, and dozens of full prep to post examples. We cover bracketed HDR, in-camera HDR, single-shot faux HDR, single-shot bracketed HDR, panoramic HDR and more! Click here for more info.
In HDR photography, the only varying factor controlling the exposure in your bracketed sequence should be the shutter speed. This means that the camera is controlling the shutter speed to give us the median exposure, the darker exposure and the brighter exposure. However, given that cameras have limitations of the highest possible shutter speed and that shutter speed also controls motion freeze, there are optimal settings for shutter speed. The optimal shutter speed depends on a few considerations, which we will discuss in this article. In addition, we will explain the two issues that arise due to shutter speed as well as why the optimal exposure value should not be at 3 stops, but at 2 stops instead.
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Issue #1: Shutter Speed Limitation
The first issue that can arise due to shutter speed is the actual shutter speed limitation caused by the camera itself. The fastest shutter speed that most DSLRs can shoot at is only 1/8000th of a second. In a 3 frame-3 stop bracketed sequence, we cannot start our median exposure at 1/2000th of a second. For example, our shutter speed is the only thing that is changing and our aperture and ISO are set to some arbitrary value. To go 1 stop darker, we go to 1/4000th of a second. To go 2 stops darker, we will be at 1/8000th of a second. To go 3 stops darker, we need to go to 1/16000th of a second. However, at 1/8000th of a second, we have already hit the shutter speed limitation. This means that our camera cannot go any lower to further reduce the brightness of the image. If we were to shoot a 3 frame-3 stop bracketed sequence, the camera would not be able to shoot the darkest image in the sequence if we started the median exposure at 1/2000th of a second since 1/8000th of a second is the darkest the camera can go and 3 stops darker needs to be at 1/16000th of a second. This is why the optimal exposure value difference should be at 2 stops instead of at 3 stops. At 3 stops, you start to run into this shutter speed limitation. In addition, you will also run into motion issues, which we will discuss later on.
However, if you want to shoot a 3 frame-3 stop bracketed sequence, the maximum shutter speed for the median exposure becomes 1/1000th of a second. At 1 stop darker, we will be at 1/2000th of a second and at 2 stops darker, we will be at 1/4000th of a second. Finally, at 3 stops darker, we will be at 1/8000th of a second, which is at the shutter speed limitation. Starting your median exposure at 1/1000th of a second will allow you to capture the darkest image in a 3 frame-3 stop bracketed sequence. At 1 stop brighter, we will be at 1/500th of a second. At 2 stops brighter, we will be at 1/250th of a second and at 3 stops brighter, we will be at 1/125th of a second.
If we are shooting a 3 frame-2 stop bracketed sequence, the maximum shutter speed for the median exposure should be 1/2000th of a second because we will be at 1/8000th of a second at 2 stops darker. To go 1 stop brighter, we would be at 1/1000th of a second and to go 2 stops brighter, we would be at 1/500th of a second.
Issue #2: Motion Blur and Ghosting
The second issue that we will run into with shutter speed is motion blur and ghosting, which are two different things. If we shoot a 3 frame-3 stop bracketed sequence, motion blur is very likely to occur, which is why it is difficult to shoot 3 frame-3 stop bracketed sequences in HDR photography. For example, if you start your median exposure at 1/500th of a second, we have to go to 1/250th of a second to go 1 stop brighter and then 1/125th of a second to go 2 stops brighter. To go 3 stops brighter, we need to go to 1/60th of a second. However, at 1/60th of a second and 1/125th of a second, we will see motion blur with moving objects that are in our scene since motion occurs when the brighter shot is at a low shutter speed. However, you can also use motion blur to your advantage by creating motion effects in your image. For example, by using a slow shutter speed, you can make the water in your scene apear smooth and silky in your image. In addition, we cannot go beyond 30 seconds, unless we are using a shutter release, when going brighter in our bracketed sequences. For example, a median exposure set at 7.5 seconds with a 3 frame-2 stop exposure sequence will be at 15 seconds at 1 stop brighter. At 2 stops brighter, we hit 30 seconds, which is the camera limitation.
Regardless of the median exposure, a 3 frame-3 stop bracketed sequence is not the best choice when shooting HDR photography.
Conclusion & Learn More!
The optimal shutter speed will really depend on the overall scene that you are shooting. The shutter speed will also depend on whether or not there are moving objects in the scene and whether or not we want to create some sort of motion effect in the scene by dragging out the shutter speed. We also need to think about if we will run into the 1/8000th of a second limitation or the 30 second limitation. These are the shutter speed considerations that we need to think about whenever we approach a scene. All these shutter speed considerations are basically the reason why we usually stick with a 3 frame-2 stop bracketed sequence. This sequence is generally the safest and will yield the best results. This bracketed sequence will also give us the widest variety in choosing shutter speeds. We will discuss this in more detail later on, but for now, understand that the optimal shutter speed for 3 frame-2 stop bracketed HDR exposures is going to be between 1/500th and 1/2000th of a second. For 3 frame-3 stop bracketed HDR exposures, your optimal shutter speed is going to be at 1/1000th of a second so that the top end peaks at 1/8000th of a second, which is most DSLRs’ shutter speed limit, and the bottom end is at 1/125th of a second, so you can freeze as much motion as possible.
For more HDR education, be sure to check out our HDR Tutorial by SLR Lounge. This comprehensive “gold standard” guide will give you a mastery of HDR photography, from the scene considerations to the actual shooting to the post production. Click here for more info.