In photography, bracketing refers to the practice of taking multiple pictures of the same scene with different exposure settings. Here, it’s a means to illustrate and better understand exposure in terms of correct exposure, under-exposure, and over-exposure. For the basics of how exposure works, please see the article Exposure, Part 1: Fundamentals.
As with all other documents in this knowledge base, this is a living document that is open to revisions. If you find anything confusing, spot any errors, or you’re left with any questions, please leave a comment or get in touch.
Objective #
The aim of this exercise is to illustrate how much the exposure (brightness) of an image changes with varying degrees of over- and under-exposure.
Why Do This Exercise? #
Given the importance of correct exposure in making good photographs, it is a practical skill to be able to look at an image that’s poorly exposed and have a sense for how the exposure needs to be changed.
What You’ll Need #
- A camera that lets you control exposure manually. This could be full manual exposure, but at very least needs to allow you to dial in exposure compensation.
- On many cameras, exposure compensation is controlled by a control wheel or knob, sometimes having its own dedicated knob. Check your camera’s manual if you aren’t sure.
- A scene with consistent lighting (consistent for ten minutes, anyway). Ideally, this scene will have a wide range of brightness, ranging from deep shade to direct sun.
- A stable place to rest the camera to keep framing consistent. A tripod is ideal for this, but it’s not critical
The composition of the images doesn’t matter, as the images you’ll make are purely to help illustrate changes in exposure. If you want to save disk space, you can set your camera to shoot in JPG format, but this isn’t especially important.
You can also perform this exercise using film. It is particularly illustrative if done using transparency (slide) film, as it is especially sensitive to variations in exposure. If you do the exercise with negative (print) film, be aware that over- and under-exposure can be compensated for at the printing stage (to a degree) and it will be harder to see the effects of different exposures. In this case, viewing the negatives directly will provide a clearer illustration. If you are making your own darkroom prints, begin with the “normal” negative, and print all other negatives at the same exposure.
Version 1: Manual Exposure Control #
If you can do the exercise outside on a sunny day between 10:00 and 14:00, your exposure will be predictable1 and you don’t need to worry about the accuracy of your meter.
Set your camera to manual exposure, set your ISO 100, set your aperture to f/11, and set your exposure to 1/250. This is your baseline exposure, what’s going to be correct under midday sun conditions in most of the world. Write it down if necessary, otherwise just keep it in mind. From there, you’re going to change to 1/2000 and make the following series of exposures, changing only the shutter speed.
- 1/2000 (3 stops underexposed)
- 1/1000 (2 stops underexposed)
- 1/500 (1 stop underexposed)
- 1/250 (correct exposure)
- 1/125 (1 stop overexposed)
- 1/60 (2 stops overexposed)
- 1/30 (3 stops overexposed.
This sequence of exposures will illustrate whole-stop differences in exposure from 3 stops underexposed to 3 stops overexposed.
If your camera’s fastest shutter speed is 1/1000 or 1/500, or if you cannot do this exercise in midday sun, you’ll need to adjust your exposures accordingly. Either way, do a series of 7 exposures, ranging from 3 stops underexposed to 3 stops overexposed. You can use your camera’s built-in meter to establish your baseline correct exposure and go from there. Consult your camera’s manual to check the specifics of how correct exposure is indicated in manual mode.
Version 2: Using the Exposure Compensation Function #
You can also do a version of this exposure using the exposure compensation control built into most cameras made from the 1980s onward. Consult your camera’s manual if you’re not sure where this control is located or how to operate it. In most cases, it will either be controlled with a wheel on the camera or with a dedicated dial. On some cameras, you may need to press a button to activate this function.
This is a good control to make use of anyway, so it’s good to become familiar with it. In some situations, light meters may be biased toward overexposure or underexposure, and the exposure compensation function is a quick way to address the problem.
Depending on your particular camera model, the exposure compensation will likely be limited to either ±2 stops or ±3 stops. If you have ±3 stops, you can do a 7 image bracket. If you have ±2 stops, just do a 5 exposure bracket. This will be a somewhat more limited illustration, but still plenty to be useful.
You can set your ISO manually, but auto ISO should be fine too if the conditions are consistent. As aperture also affects depth of field, I recommend that you manually set your aperture to f/8 or f/11. Set the camera to Aperture Priority mode (marked Av or A on most cameras). Make the following exposures:
- Exposure compensation set to -3 stops (if available)
- Exposure compensation set to -2 stops
- Exposure compensation set to -1 stop
- Exposure compensation set to 0 (center position)
- Exposure compensation set to +1 stop
- Exposure compensation set to +2 stops
- Exposure compensation set to +3 stops (if available)
Reviewing Your Results #
Once you’ve made your exposures, import your files onto your computer, ideally into a program like Adobe Lightroom that will display EXIF data (your exposure settings) and a histogram. Your series of exposures should look something like the following.
Note that the brightness of your display will affect the appearance of the images below. Also, I will be re-shooting these images, as I noticed an error after the fact and all the images appear slightly darker than normal. For now, though, you get the idea.
A full stop of difference in exposure is easy to see. Naturally, smaller differences in exposure are likely to be harder to discern, but it doesn’t take much time to get a sense for it and be able to notice differences of a half or a quarter of a stop.
Part of the value of this exercise is that, once you develop a sense for how much an exposure is off, you can more quickly adjust your exposure on the fly. If you got that very last exposure, for example, you’d know you’d need to reduce exposure by 2-3 stops, depending on the scene. You could do so by adjusting shutter speed, aperture, ISO, or a combination of the three.
Additional Information #
When you look at your images on the computer, you should also be able to see a histogram that represents the number of pixels that fall into each exposure value from 0 (minimum) to 255 (maximum, pure white). In RGB color, each of the red, green, and blue channel values should be represented in the histogram, along with the combined values. The histogram of our baseline exposure looks like this:
When I went out to shoot these images during my lunch break, I failed to notice that it was actually ever-so-slightly overcast, which led to this exposure being just a tad underexposed. The next exposure in the series, actually displays a more favorable histogram overall:
As you can see, there is a better overall distribution of tones throughout the histogram. There also isn’t any clipping, which is what it’s called when areas of the photo fall below the minimum exposure level and detail is lost where it goes fully black, or on the opposite end when brightness exceeds the sensor’s ability to record and detail is lost in areas because they go pure white.
In the darkest shot, we can see in the histogram and in the image itself that we are clipping the shadows (represented by the areas masked in blue):
In the brightest shot, we can see in the histogram and in the image itself that we are clipping in the highlights (represented by the areas masked in red):
Clipping isn’t always avoidable, but it also doesn’t always matter. It will depend on the particular shot. During night photography, for example, when overall contrast tends to be much higher than during the day, clipping some in both the shadows and the highlights may be inevitable.
There is also the concept of exposing to the right, which is the idea of trying to optimize for the maximum amount of information contained in your file by giving the most amount of exposure possible for a scene without introducing clipping in the highlights. You can manage this at the time of exposure by checking the histogram on your digital camera, which you should be able to configure to indicate if/where clipping is occurring.
Working this way isn’t always practical, and may not be worth the effort (or even possible, under certain conditions), but it’s at least good to know about.
- This is the Sunny 16 Rule in effect. Under conditions of midday sun, you can set your aperture to f/16 and your shutter speed to roughly 1/X, where X is your ISO. If your ISO is set to 100, for example, your shutter speed would be 1/100 (or 1/125 for cameras without a 1/100 option). With ISO 200, 1/200 or 1/250. With ISO 400, you can shoot at 1/400 or 1/500. The small difference between speeds like 1/100 and 1/125 is negligible for our purposes. This rule is reliable and especially useful with film cameras without light meters. In this exercise, I’ve instructed the use of f/11, which then requires a 1-stop change of shutter speed from 1/125 to 1/250. In most cases, unless you really need the additional depth of field, it’s likely better to shoot at f/11, as your lens will give a sharper image than at f/16 (due to diffraction). ↩︎
