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Understanding exposure

Sailboat in the sunrise, example of a landscape photograph

Getting Good Exposure: The absolute, essential elements

This is the first in a series of blog posts intended to help guide those who are new to photography, or who want to take their photography to a higher level. Those who want to take more than just snapshots. This post is not intended to make you a professional photographer. It will probably not be of much, if any help to a skilled amateur photographer. It is intended to give simple but accurate explanations of one of the key elements of photography, exposure. As a consumer I have bought and discarded all too many useless how-to books. What I will try to do is distill down the key factors needed to take good pictures. I will also give references to some of the really good sources that I have used in learning, so that if you wish to delve deeper you can do so without the trial and error process that I went through.

This post is also not about how to use a specific camera. To use the information presented here you will have to know how to use your camera, or read the manual, or read one of the how-to-use-your-specific-camera books.

I am not in any way affiliated with, or paid by any person or brand mentioned in this post. I recommend them simply because they are good, and deserve the credit. But even more importantly I mention them because they are valuable resources for you to continue your quest for better photographs. And that is what this post is all about.

Many of the things I say here are printed in the various “tips on how to shoot like a professional” books. But you would have to read a number of books, covering a lot of material (and often presented in more difficult terms) just to find them. But in all fairness, I will also tell you about the best of the resources I have found. I try to give you all of the important information here; however it is quite admittedly on a very basic level. The books I reference are great resources, and written by highly skilled photographers who know how to explain their trade. The three authors I recommend highly for a number of books are Scott Kelby, Bryan Peterson and Rick Sammon. There are other authors that have written individual books that I can recommend, but these guys have written several each that are top notch, and I would not hesitate to buy a book they have authored.

To see some of my photographs please visit my website at http://www.waltpayne.photography

An Introduction to Exposure

There are three elements to attaining proper exposure. They all interact with each other, and by balancing them properly you can achieve proper exposure with many variations of those settings. But proper exposure alone will not always give you a good photograph, or the one you “see” in your mind. This is one of several problems with using Auto Mode on your camera. What if you want to freeze the action? Or maybe the opposite, what if you want some blur, to show motion? What if you want to have perfect focus on the subject, but have the background blurred? Those are all very basic effects that any skilled amateur can attain with minimal effort. But not in Auto Mode! The three elements effecting exposure are ISO, aperture and shutter speed.

ISO

ISO represents the sensitivity of your camera’s sensor to light. Some of you might remember the old term ASA. Same thing. ISO can vary from under 100 to as high as 25,000 on some of the digital SLRs and newer mirrorless cameras. The bigger the number, the more light sensed. So why not just go for the biggest setting and be done with it? Well, just like with film, there is a trade-off for that sensitivity. In film it was called grain, in digital terms it is noise. The higher the ISO, the more noise you will get. So you will want to keep the setting as low as possible. But what if you can’t? What if it is dark, and you can’t use flash? Well, if you must, use a higher setting. But do so knowing that you are compromising the quality of your photographs, at least to some extent, in favor of getting a picture of some quality, versus not getting it any all. And, there is one thing you can do to decrease the noise significantly. Where it is located on the menu varies by camera, but most decent digital cameras have a camera setting for automatic noise reduction. It helps a lot. The problem is that as usual there is a price, a trade-off. Whatever shutter speed you use, it will take at least that long for the noise reduction algorithm to work. That is because it takes a totally black picture right after the actual exposure, and looks for false sensitivity readings. It then subtracts out that noise from your photograph. You will get much better quality, but it can really slow things down sometimes, and depending on the shutter speed it could totally prevent you from using Burst Mode, also known as Continuous Mode.

There are also a number of software programs that have some success with reducing noise in digital photographs. If you need to do much high ISO photography it would be worth investigating those programs.

Aperture

Aperture is the variable size of the opening in the lens, letting in light at a rate that can be adjusted. It is expressed in “f-stops”. The smaller the number, the bigger the opening, hence the more light that the lens allows to strike the digital sensor. But there is also a side effect of adjusting the aperture that can either help you make much better photographs, or ruin the perfect shot. It is called depth of field. Depth of field, as you might guess, is the term used to indicate how far in front of and behind the focal point the “in-focus” area of the photograph extends.

Shutter Speed

By adjusting your shutter speed you also affect how much light reaches the sensor. The longer the shutter is open, the more light will reach the sensor. But just as the other two settings that effect exposure have side effects, so does the shutter speed. As you decrease shutter speed settings, you will reach a point where the shutter is not open long enough to freeze the motion in the picture. As with the other side effects, this can make a good photograph into a great one, or it can absolutely ruin that chance of a lifetime shot. It is up to you to control it to take advantage of this effect when appropriate, and eliminate it as a factor when it is undesired.

Exposure, and putting it all together

This is where I do my really hard sell for getting out of Auto Mode. I will not try to sell you on Manual Mode. Hopefully you will get there yourself, but to be honest Manual Mode is something that has advantages that are mostly beyond the needs of less advanced photographers. Master the basics like Aperture Priority and Shutter Priority, then Manual Mode will make more sense. And it is more difficult to master than the other camera modes. However it is really quite easy to use Aperture Priority Mode and Shutter Priority Mode. When used with Exposure Compensation they will give you an amazing amount of control over your photographs in an amazingly simple fashion.

ISO Settings

It is important that you not leave your camera on the default setting for ISO. That default setting is Auto ISO, which means the camera will potentially choose an ISO as high as 3200, or higher if you allow it. Yes, you will get the photograph, but will you want to use it for anything? Better to be forced to set it manually so that you can make choices about how to get the best quality photograph you can under the existing conditions.

Exercise: There have been significant advances in noise reduction in the newer digital cameras. Take a number of photographs of the same object, under the same lighting conditions, while varying the ISO settings. Look at these photographs on your computer monitor. But go beyond the size of your monitor. Enlarge them, and look for “grain.” Determine where the quality begins to deteriorate. That will be an important discovery for use in taking low light photographs in the future. Digital cameras are improving at a fast pace. ISO settings are able to be set higher and higher without much noise. Find out what works for you. But look at the photographs at a high magnification. Consider what the results will be if you get that great shot and want to print it poster sized. That is an option that is now very affordable, so don’t rule it out. Don’t forget to also test the automatic noise reduction. Note the degree of improvement, and when it is most useful. Again, this information could help you get that shot of a lifetime.

Aperture Priority Mode

Setting your camera to Aperture Priority Mode will, as the name might imply, give you direct control over the aperture, or opening of the lens. You should choose this setting when you want control over the depth of field. When you are in Aperture Priority Mode, the camera will choose the other settings for you. If you took your ISO setting out of Auto Mode, that only leaves Shutter Speed. So the thing that makes Aperture Priority Mode so much better than Auto Mode is that you choose the setting that is most appropriate for the depth of field you want, and then the camera selects the right Shutter Speed to get a good exposure. You get the best of both worlds, automation but under your control.

Exercise: Do the same type of experimenting as you did with ISO, only now set your ISO to the lowest setting and put your camera in Aperture Priority mode and take lots of experimental photos. Take the same photograph using different aperture settings. Look at the varying depth of field. Notice that you will get a good exposure at a lot of different aperture settings, but the depth of field varies widely across the range of good exposures. This is where leaving Auto Mode becomes both important and easy to do. It gives you a lot more control over the type of photgarphs you take.

Shutter Priority Mode

Shutter Priority Mode is for the times when shutter speed is the primary consideration. Sporting events, that fidgety nephew of yours, birds in flight, etc. Or what if you want to do something a little artistic with your photography? Say you want to photograph your daughter’s ballet performance but you want some of the pictures to capture the essence of motion, not just freeze her in place. Or what if you want to get that smooth, creamy look when photographing a stream or waterfall. If you tried to do these things in Auto Mode, your camera would think it knows best. It would probably give you a perfect exposure. And a perfectly common, boring photograph. 

Just as Aperture Priority Mode allows you to control the Aperture, Shutter Priority Mode allows you to control the shutter speed, and your camera will select the appropriate aperture to create a good exposure.

Exercise: Now it’s time to experiment with shutter speed. Set your camera in shutter priority mode, and find a subject in motion. Maybe a pet, a child, or even cars on a local street. Vary the shutter speed, and watch what happens to your photographs. Again, although the camera picks an aperture that creates a good exposure, the look of the photographs will vary immensely. Try photographing a faucet with the water running, simulating a waterfall, and use varying shutter speeds. Note how the faster shutter speeds will freeze the motion so you can almost see individual droplets, and the slower shutter speeds will create that creamy, milky look. Especially if you have the right light to allow a really slow shutter speed.

Checking the Exposure

You can somewhat tell if you got a good exposure by looking at the image on your LCD screen. But at 3” in size (or less, depending on your camera) it only gives you a look at the obvious. Since your camera is taking the exposure based upon it’s metering system, it will do the best it can. But if you have a wide range of lighting conditions, it will not be perfect. Look at both the lighter areas and the shadows. See if you have detail in both.

There are several things you can do that are very quick and easy once you get used to them. One is to use the histogram. Using the luminance histogram is a good start. If any part of the peaks shown on the graph touch the left or right side it means that at least some part of your picture has areas where your dark areas are pure black with no detail, and/or your light areas are pure white with no detail. If the graph shows an area touching the left side, that means you have shadow details that are being lost, or clipped. If the graph shows an area touching the right side, that means you have highlight (light) areas that are losing detail. Either of those individually can be adjusted for by using Exposure Compensation.

If you want a more accurate representation of your exposure, you can use the RGB histogram. This will tell you if any of the primary colors are being clipped. It is possible, for example, to have red clipped while blue and green are well enough within range to bring the overall luminance graph into the proper range so that you would think you have not lost any detail. So while the luminance histogram is a quick, easy way to check exposure, the RGB histogram is the more accurate representation.

Another way to determine if your highlights are overexposed is to use the Highlight Alert setting on your camera. This creates what are commonly referred to as “The Blinkies” when viewing the photograph on your LCD screen. If any area of the photograph has overexposed highlights, they will blink, making it obvious that you have lost highlight detail. You can then use Exposure Compensation to adjust the exposure. Highlight alert is an easy to use setting and should definitly be used. Unfortunately there is no such alert for lost shadow detail, which plays an equally important role in getting a great photograph.

Most cameras allow you to zoom in on the LCD screen to look at the details and determine if you got the shot you wanted. That includes both exposure and focus. Any shot that looks out of focus on your camera’s LCD screen without zooming is really bad. It is just too hard to tell if it is good on that small of an image.

Many newer dSLR cameras also include a cable that allows you to shoot in what is called tethered mode. You can see the photographs on your computer screen as you take them. This is a great tool for experimenting, so you can easily see the results as they occur. A new kind of cable has recently shown up on the market, a USB extension that is over 6’ long is now available. I suggest going with the 16’ length, as they seem to be more reliable. Professional photographers are starting to use tethered mode for studio work, as it allows them to get immediate feedback on the lighting and composition of their shots.

Exposure Compensation

Once you learn how to use them, through practice and experience, Aperture Priority and Shutter Priority Modes give you a much better chance of capturing that perfect photograph. But … they still depend on your camera’s ability to sense the right setting needed. Cameras have become very advanced computerized devices that are quite good at what they do. However, they are still a bit limited in some respects. They cannot sense nearly the range of color and light that the human eye can sense. So they have a way for you to override the camera’s choice. If you check your exposure as described above and for some reason the photograph is not properly exposed, you can use the Exposure Compensation settings to tell the camera to allow more or less light to reach the sensor. Exposure Compensation allows you to adjust the light incrementally by fractions of an f-Stop to increase or decrease the amount of light that reaches the sensor. So if, for example you decide that Aperture Priority is the right method to capture the image you want, you are taking control of the ISO by setting it in the range you know is most appropriate, and you are controlling the Aperture. The camera then takes control of calculating the best shutter speed. But sometimes the lighting conditions can fool the camera and cause it to choose a wrong setting for what you want. This is especially true if you have a significant amount of either white or dark (especially black) areas involved. That is because the camera’s light metering system works based on reflected light, so too much reflected light from one area will cause the overall shot to be too dark, and too little from one area can cause the overall shot to be overexposed, or too light.

HDR Photography

Sometimes you want to take a photograph that has a silhouette. When shot against a stunning background it can be a nice touch that takes that beautiful sunset or sunrise shot to a higher level. But what if you wanted to capture both the brightness of the sun rising over the bay, and the deep shadowy rocks lining the shore? Or the sun setting over that beautiful snow-capped mountain, but you also wanted to capture the details of the rocky canyons? Our eyes can see a wide range of light values, and colors. But although digital cameras have made great strides in accurately capturing what we see, they still only capture a range of a little more than 5 f-stops of light. Our eyes can see more than double that. That is one reason why we are sometimes disappointed in our photographs. Sometimes the camera can capture enough of the details of what we see to look realistic, but other times we take a photograph and it just lacks something, but we don’t know what. That “what” is the details hidden in the shadows, or the range of color that a camera can’t quite capture.

Exposure Compensation allows you to compensate to an extent for either lost shadow detail, or lost highlight detail. But what if there is such an extreme variation in light and color range that you can’t balance the two? There is a relatively new art in photography called High Dynamic Range (HDR) Photography. It uses multiple photographs taken from the same exact position, at different exposures over a range of f-stops, to capture a fuller range of light and color. These exposures are then blended together using computer software to create a photograph that captures both the highlight and shadow details. This technique can also be used to create an artistic look by displaying a much wider range of color and/or light than a single photograph might capture. It might sound complicated, but to be honest if you understand the basics of exposure covered in this book then you know the fundamentals needed to take stunning HDR photographs. Much of HDR photography involves no more than having a good software program. There are several really good, respected programs that are specifically designed for processing HDR photographs. And I know that at least a few have free downloads that you can use to try them out.

Other than this brief explanation, this technique is beyond the scope of this post. There are many good books available on this topic. One that I have read and learned a lot from is “The HDR Book” by Rafael “RC” Concepcion.  He explains how to process HDR photographs using the most commonly used programs, Photoshop CS5TM, Photomatix ProTM and HDE Efex ProTM. If you go through his book trying out the techniques using the demos of each you should be able to make an informed decision about which one suits your needs the best, assuming you want to invest a little time and money in this technique. The book goes beyond just how to do it, though. It also discusses in depth the WHAT of HDR photography, by discussing the kinds of subjects that benefit the most from using HDR techniques. Although it really is not a difficult technique to learn, HDR photography is not by any means a beginner technique, which is the intended target for this series.

Exposure: Taking it to the Next Level

This post is intended to simplify the task of finding the useful information and resources about photography. But there is, as they say, no substitute for experience. Luckily, once you make that initial investment, digital photography is free. At least until you decide you want to expand into an area that requires further investment. Take photographs often. Photograph things you are interested in, and things you love. Photograph your flowers, your pets, your kids, or a nearby park. Photograph anything. Experiment. On a rainy day, spend some time indoors just photographing anything. Take photographs that you know you will throw away. But experiment with light, exposure, focus … practice. Learn. Gain experience with how your camera works.  Great shots sometimes depend on knowing your camera well enough to react quickly to circumstances. Being able to change the settings without fumbling around can be the difference between a great shot and a missed opportunity. But this is also where I tell you that never using Auto Mode is not any better than always using Auto Mode. Instead, I suggest practicing enough with all of your camera’s modes so that you are quite familiar with their strengths and limitations. Knowing when you can safely use Auto Mode can help you get that great shot as much as any other method. Being able to quickly put your camera into Auto Mode, or Sport Mode, or Portrait Mode, etc. can allow you to get a shot with minimal decisions and adjustments, but only if they are an appropriate choice for the circumstances.

If you want a great source of in-depth information on the topic of exposure, read “Understanding Exposure” by Bryan Peterson. It is a well-written book, with lots of great photographs to illustrate the points he is discussing. And it is written to be very understandable for all levels of experience. I have read three of his books, and would have to say he does a great job. I would not hesitate to buy any of Mr. Peterson’s books.

Copyright 2021 Walt Payne Photography – All rights reserved.

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