Understanding exposure in photography is just as important as knowing when to press the shutter button. Your exposure settings—aperture, shutter speed, and ISO—impact how your images turn out. Yet, many photographers overlook a powerful tool: the histogram. Over the past six months in the field with clients of all photographic levels this has been a common theme, thus this article. In this article, I explain the connections between histograms and exposure settings, provide insights on how to avoid overexposure or underexposure, and share practical examples of analyzing histograms in different lighting conditions.
The Basics of Exposure Settings
Before we jump into histograms, let’s review the essential components of exposure: aperture, shutter speed, and ISO.
Aperture affects the amount of light entering your lens and impacts the depth of field. For instance, a wide aperture (like f/2.8) allows more light and creates a soft background, while a narrow aperture (like f/16) lets in less light and keeps more of the image in focus.
Shutter speed determines how long your camera's shutter is open, affecting motion blur. For example, a shutter speed of 1/2500 sec can freeze an action shot of a bird in flight, while a speed of 1/3 sec captures the silky movement of a waterfall.
ISO measures the camera's sensitivity to light. A low ISO (like 100) delivers clear images with minimal to no noise, while a higher ISO (like 3200+) is useful in low-light conditions, though it may introduce graininess.
All three settings work together to create the overall image exposure, and histograms visually show how they combine to create your images.
Understanding Histograms
A histogram is a graphical representation of the tonal values in your image. The x-axis displays brightness levels, with shadows on the left and highlights on the right. The y-axis shows the number of pixels at each brightness level.
When you review a histogram after taking a photo, you're assessing how light is distributed throughout the shot. Traditionally, a well-balanced histogram peaks in the mid-tones with gentle slopes toward the shadows and highlights (think ideal bell-curve).
If the histogram heavily leans left, your image is probably underexposed (too dark).
If it crowds the right side, your photo is likely overexposed (too bright).
The idea of "expose to the right," ETTR, is often mentioned as a way to fully collect all data present in a scene and then be able to develop or post-process it as the artist likes after the fact.
These "rules" assume a typical scene rather than a dark or bright scene. If you have a very dark scene your histogram may be to the left as pushing to the right can overexpose what are actually black/dark grey tones. The same goes for if you have a very bright scene, such as snow. Underexposing to put the histogram more in the "center" will leave you with grey snow and an underexposed image that has to be brightened in post processing, potentially adding noise.
Ideally, you should aim to reach a level where you not only know how to interpret the histogram and adjust the exposure based on its information, but also how to assess your scene and estimate what the histogram will display for that exposure.
Utilizing Histograms to Avoid Exposure Errors
With the advent of mirrorless cameras that display live histograms, it has never been easier to avoid exposure errors. Personally, it is this live histogram feature alone that, to me, makes transitioning from a DSLR to mirrorless worth the price and effort.
Avoiding overexposure and underexposure is key to mastering exposure. Here’s how to use histograms to guide your adjustments:
Regularly check your histogram when changing camera settings. If the histogram shifts left, open your aperture wider, slow your shutter speed, or boost your ISO. By doing this, you enhance your chances of capturing well-exposed images.
If your histogram skews right, close down your aperture, increase your shutter speed, or lower your ISO. This practice will help you correct exposure and encourage a thoughtful approach to capturing images.
In a high dynamic lighting situation where you have both strong highlights (where histogram skews to the right) and strong shadows (where histogram skews to the left) and you either don't want or are unable to bracket the scene, protect your highlights. Allow the shadows to be clipped, but protect and do not overexpose the highlights as a viewer's eyes go to the brightest areas of the image first. In doing so, we expect to see detail in those bright areas, especially if they are in focus (like the feathers on a heron). If overexposed, the detail data is lost in those pixels and cannot be recovered. Whereas, in the shadows, our brains are more forgiving if we do not see all the detail because we are use to not seeing all detail in darker areas naturally.
Practical Examples of Histogram Analysis
Example 1: Bright Sunny Day
Picture yourself photographing a vibrant field of flowers on a bright, sunny day. This high contrast between the colorful flowers and blue sky may cause exposure problems.
Looking at the histogram (live if on mirrorless or after taking the first shot if on DSLR), you notice the histogram is pushed to the right, indicating overexposure. The bright flowers lose detail.
To fix this, consider:
Reducing your aperture size (increasing the f-number, like from f/7.1 to f/16).
Increasing the shutter speed (e.g., from 1/500 sec to 1/2000 sec).
Lowering your ISO (e.g., from 400 to 100).
These adjustments can help balance the histogram and preserve important details in the highlights.
Example 2: Golden Hour
The golden hour, just after sunrise or before sunset, casts beautiful warm light. However, this lighting can trick your exposure settings - but not your histogram!
While shooting a landscape during golden hour, you might see a histogram with a peak in mid-tones but a lack of highlights. This often happens in shadow-heavy scenes like mountains.
To improve this, you might:
Open your aperture wider (e.g., from f/11 to f/5.6).
Decrease your shutter speed (e.g., from 1/500 sec to 1/250 sec).
After each adjustment, check your histogram for balance.
Example 3: Low-Light Conditions
In low-light scenarios, such as a forest at dusk, capturing details proves challenging. Here, your histograms may lean left, indicating underexposure or that you have a proper exposure for the dark scene in front of you, depending on your artistic choices.
To address this, consider:
Increasing your ISO (e.g., from 800 to 1600).
Opening up your aperture (e.g., from f/8 to f/6.3).
Slowing your shutter speed (e.g., from 1/125 sec to 1/60 sec).
Be careful with high ISO settings as they can introduce noise but do not be afraid of your ISO. It is better to have a sharp, noisy image than a blurry one. Use your histogram to find that balance.
Mastering Histograms for Better Photos
Understanding histograms is essential for photographers wanting to excel in exposure. By analyzing the light distribution in your images, you can make informed adjustments to your aperture, shutter speed, and ISO settings. This will help you avoid common exposure errors.
Whether you're shooting in bright daylight, during the enchanting golden hour, or in challenging low-light conditions, make checking your histogram a habit. With time and practice, you will unlock the full potential of this tool, enhancing your nature photography and capturing stunning images that showcase the beauty around you.
Happy photography, and remember to keep an eye on your histogram!
Want hands-on help in learning how to use your histogram? I cover this on every tour and workshop I lead, I think it is that important of a tool. So consider joining me in one of the many amazing locations I guide to where you will not only walk away with new stories and beautiful images but also improved photographic skills to use everywhere going forward. Check out my Photo Adventure schedule here for upcoming tours and workshops.
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