Night Photography Class

This section is for anyone who is new to photography or those who’ve never used any setting other than “Auto” mode. If you’re already familiar with program modes and exposure settings like aperture, shutter speed, and ISO, you can probably skip this section.

All the different modes and terms may seem a bit confusing but don’t be intimidated. The information we’ll be covering here is critical if you want to capture amazing photos at night. And, while it may seem like a lot to learn, there are really just a handful of fundamentals that you need to understand in order to take your photography to the next level.

The skills and concepts you’re about to learn have been used by photographers for the last hundred years but many modern-day photo enthusiasts aren’t familiar with them because today’s cameras do so much of the work for you. Innovations like auto-focus, auto-exposure, and the many other automatic functions performed by your camera are relatively recent developments.

Although you may have seen references to some of your camera’s more advanced features like Shutter Priority, Aperture Priority, and Manual program modes in the instruction manual, they may have seemed a little intimidating or you may have wondered why you should use them at all when you can just set everything to “Auto” and go. This section is going to show you not only how to use these creative camera modes but also why you should use them.

Today’s digital cameras are really quite incredible. You can create great photos just by pointing and shooting. But behind the scenes there’s an amazing amount of calculations taking place. Your camera is “seeing” the light coming in through the lens and determining the best combination of settings to achieve an accurate exposure. It wasn’t so long ago that all this had to be done manually by the photographer.

However, as good as today’s cameras are at determining the appropriate settings, there are still situations where the photographer must intervene in order to achieve the desired result. Night photography is one of those situations. As good as your camera may be during the day, once the sun goes down all bets are off.

The basic driving force in photography is light. After all, photography is the act of capturing light. Instead of film, your camera has an electronic sensor that records the light that strikes it. The total amount of light that is allowed to fall on the sensor while taking a picture is referred to as the exposure. A proper exposure results in a good photo. Too much light and the photo is overexposed. Too little and the photo is underexposed. An overexposed photo is washed out and bleached looking while an underexposed photo is very dark. Both conditions result in images that are lacking detail, either in the highlight areas or the shadow areas.

There are three different settings that control exposure. In Auto mode, your camera configures these for you. In order to take good photos at night, you’ll need to know what these settings are and how they relate to each other so you can set them yourself.

Shutter Speed

The first setting you’ll need to understand is shutter speed. This is the length of time the camera’s shutter is open and is measured in seconds or fractions of a second. Some typical shutter speeds are: 1s, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/125s, 1/250s,1/500s, and 1/1000s.

While the shutter is open, light is striking the camera’s sensor. When the shutter is closed, no light can get through. Faster shutter speeds, in which the shutter is open for a very short amount of time, are used to “freeze” action. This is used a lot in sports photography when the photographer wants to capture a fast moving subject. Slower shutter speeds, in which the shutter is open for a longer period of time, can be used to show motion. If you’ve ever seen a photo of a waterfall where the water is blurry and smooth, a slow shutter speed was used. Slow shutter speeds are also used in low light and night photography. Because of the small amount of ambient light present, shutter speeds of several seconds or minutes are often necessary.

Aperture

Aperture refers to the diaphragm opening inside a photographic lens. The size of the diaphragm opening regulates the amount of light that passes through the lens and onto the camera’s sensor when the shutter opens during the exposure process. Think of it like the pupil in your eye. The wider it is, the more light is allowed through. The smaller it is, the less light.

Aperture size is usually calibrated in f-numbers or f-stops. Some typical f-stops include f/32, f/22, f/16, f/11, f/8, f/5.6, f/4.0, f/2.8, f/2, and f/1.4. It’s important to note that the larger the f-number, the smaller the aperture opening is and vice versa. For example, an aperture set at f/2.8 is much wider and therefore will allow more light through the lens than an aperture set at f/22. The example above shows the aperture opening of a lens at various f-stops.

Each f-stop in the sequence allows either twice as much light or half as much light as the f-stop before it depending on which direction you’re moving. If the aperture was set at f/8 and you switched it to f/11(smaller aperture opening), you would cut the amount of light entering through the lens in half. If you switched from f/8 to f/5.6 (larger aperture opening) you would double the amount of light entering through the lens. This is critical to understand because of the relationship between aperture size and shutter speed which I’ll be discussing shortly.

With older lenses, the aperture size was set on the lens itself. The image of the left shows an old lens with the aperture setting dial. Modern lenses don’t have an aperture dial on the lens. Instead the aperture size is controlled by the camera and the diaphragm doesn’t close until the moment the photo is taken.

Aperture size can also be used to control depth of field. Depth of field refers to how much of the image is in focus, relative to the focal point. Depth of field can be deep, shallow, or anywhere in between. A landscape photograph where everything in the scene is in sharp focus is an example of a deep depth of field. A good example of a shallow depth of field is a portrait where the subject is in focus but the background is blurry.

Depth of field varies with the size of the aperture. A wider aperture (lower f-number), will result in a shallower depth of field. A smaller aperture opening (higher f-number) will result in a deeper depth of field. Portrait photographers often use wide apertures to create a shallow depth of field which helps separate the subject from the background. As a landscape photographer, I often use a small aperture to make sure the foreground and background are nice and sharp.

In night photography, we’re usually more concerned with aperture size as it relates to the amount of light coming through the lens than with depth of field. However, there are times when depth of field may be an issue and those situations will be noted as the various techniques are discussed.

In the example above, the difference in depth of field between f/22 and f/2.8 is quite obvious. In both cases, the camera was focused on the front of the mailbox.

ISO

ISO denotes how sensitive the camera’s sensor is to light. The higher the ISO, the more sensitive it becomes. A higher ISO setting will allow you to use a faster shutter speed which can be important in low-light situations. However, the higher the ISO setting, the more noise is generated in the photo so you always want to use the lowest ISO setting that will work in a given situation. Noise is the digital equivalent of film grain and looks a bit like TV static. It’s usually more prevalent in the darker areas of a photo so it’s often more noticeable in night images.

Typical ISO settings include ISO 50, 100, 200, 400, 800, 1600, and 3200. Don’t worry if your camera doesn’t have all of these. Most cameras have ISO 100, 200, 400 and 800 which is a useful range for most situations.

In case you’re wondering, ISO stands for “International Organization for Standardization” and is a standard for all digital sensors.

Putting It All Together

Shutter speed, aperture, and ISO work together to determine the exposure for a photograph. Let’s review the following:

Shutter Speed: Controls the length of time that light is allowed to fall on the sensor.

Aperture: Controls the amount of light that enters through the lens.

ISO: Determines how sensitive the sensor is to the light that falls on it.

Exposure: The total amount of light that is allowed to fall on the sensor, as determined by the combination of aperture and shutter speed.

In “Auto” mode, your camera determines the correct settings for shutter speed, aperture, and ISO to obtain the proper exposure. However, for night photography you’ll often need to manually make adjustments to all three. Before you can do that you’ll need to understand the relationship between them.

As stated earlier, the three settings work together to determine a photograph’s exposure. If all three are set correctly, the photo will be properly exposed. However, just because a photo is properly exposed doesn’t mean you’ll get the result your want. There may be times when you want to increase or decrease the shutter speed or adjust the aperture setting to create a desired effect. You can do this and still maintain a proper exposure by adjusting the other settings accordingly.

For example, if I wanted to slow down the shutter speed while maintaining a proper exposure I would either need to reduce the aperture size so less light is passing through the lens or lower the ISO setting so the sensor is less sensitive to light. Each action requires that the shutter stay open longer, either to compensate for the reduced amount of light coming through the lens or the decreased sensitivity of the sensor.

If I wanted to increase the shutter speed I could use a wider aperture so more light is allowed through the lens or increase the ISO setting so the sensor is more sensitive to light. Each action requires that the shutter stay open for less time, either to compensate for the increased amount of light coming through the lens or the greater sensitivity of the sensor.

In the examples above, I could also change both the aperture and ISO settings which would more dramatically affect the shutter speed.

Let’s say that I’m taking some outdoor photos at a family reunion and it’s early evening and the light is starting to fade. As I’m taking the photos I realize that some of them are starting to come out blurry, especially ones where people are moving. I have my camera set to ISO 100 and it’s automatically determining the correct shutter speed and aperture. I notice on my display screen that the camera has set the aperture to F/3.5 which is the widest aperture available on my particular lens, and the shutter speed is set to 1/50 second. I want to increase the shutter speed to 1/100 second because 1/50 second is just too slow to freeze the movement of the people who are moving around.

The problem is that if I only increase the shutter speed, doubling it from 1/50 second to 1/100 second, I’m cutting the length of time that light is allowed to fall on the sensor in half, which will underexpose the image. A wider aperture would allow more light through the lens and allow me to increase the shutter speed while maintaining a correct exposure but the camera is already set at the widest aperture my lens has to offer. In this scenario, the only way I can increase my shutter speed while maintaining a correct exposure is to increase the ISO setting.

By increasing the ISO setting from 100 to 200 I’m doubling the sensitivity of the sensor. Therefore, I can also double the shutter speed from 1/50 second to 1/100 second and still maintain a proper exposure. If I then decided that 1/100 second wasn’t fast enough and wanted to increase it to 1/200 second I could again double the ISO from 200 to 400 and maintain the correct exposure.

Let’s use the above scenario again only this time I’m using a lens that offers an aperture as large as F/2.8 and I currently have it set to F/5.6. If I want to increase my shutter speed from 1/50 second to 1/100 second while maintaining a correct exposure I can increase the ISO or I can enlarge the aperture, changing it from F/5.6 to F/4. With the latter option, I’m enlarging the aperture opening to allow twice the amount of light to enter the lens, thereby making it possible to double the shutter speed and maintain the correct exposure.

When doing night photography, you’ll often come across a scene that requires a shutter speed that’s longer than your camera can handle. Let’s say that the longest shutter speed your camera allows is 30 seconds. You set up the camera to take the shot and it alerts you that the scene requires a shutter speed longer than the 30 second limit. If the ISO is set to 100 you can increase it to 200 and see if the shutter speed then falls into the range of the camera. If not, keep increasing the ISO until it does.

Of course, if your camera has a Bulb mode you don’t have to worry about that but you still might like to know what the correct exposure is so you can time it. Let’s say you want to shoot at ISO 100 to keep noise to a minimum but your camera indicates that the correct exposure is longer than 30 seconds (assuming that 30 seconds is the longest shutter speed your camera allows). Following the method above you increase the ISO until the shutter speed falls back into the range of the camera. You find that at ISO 400, the camera meters a shutter speed of 20 seconds. By working backwards, you can determine what the correct shutter speed would be at ISO 100. At ISO 200 the correct shutter speed would be 40 seconds and at ISO 100 it would be 80 seconds. You can then switch to Bulb mode and time an 80 second exposure at ISO 100.

This interdependent relationship between shutter speed, aperture, and ISO is called reciprocity. It’s a very useful tool because often you want to increase or decrease the shutter speed or use varying aperture sizes for depth of field effects.

The good news is that you don’t have to do it all manually. In addition to the “Auto” and “Manual” modes on your camera, you also have Aperture Priority Mode and Shutter Priority Mode. These are denoted in various ways on the function dial if you have a digital SLR. In the example on the right, Av is aperture priority and Tv is shutter priority but yours may denoted differently. If you’re using a point and shoot type camera you may have to access the different modes through the menu system.

Aperture Priority Mode

Aperture priority mode allows you to manually set the aperture you wish to use. This mode is useful when you want to ensure a particular aperture to control depth of field in a scene such as a landscape or portrait. In aperture priority mode, the camera will automatically choose the correct shutter speed based on the aperture you select.

Shutter Priority Mode

Shutter priority mode allows you to manually set the shutter speed. This mode is useful when you want to use a particular shutter speed. In shutter priority mode, the camera will automatically choose the correct aperture based on the shutter speed you select.

Manual Mode

In manual mode, you control the shutter speed and aperture and can set them independently of each other.

Which One to Use
So which one should you use? It depends on what you’re trying to do. Say you’re doing some shots of a local sports team during a game and you want to be able to “freeze” the action. In this case you’d want to use Shutter Priority Mode and set a fast shutter speed, like 1/500 second and allow the camera to choose the correct aperture.

**Note: If you’re lens has a limited aperture range you may not be able to maintain a fast shutter speed if there’s not enough ambient light such as on an overcast day. In this case, using a higher ISO will allow you to maintain a faster shutter speed.

If you’re shooting some landscapes and want to ensure a “deep” depth of field you’d want to use Aperture Priority Mode and set a small aperture, like F/16. Conversely, if you’re shooting a portrait you may want to maintain a large aperture to create a shallow depth of field so you can better separate your subject from the background.

I’ll be referencing aperture, shutter speed, and ISO a lot more when discussing the various techniques on this iste. Don’t worry if you’re still not quite sure how to use them. They’ll start to make more sense as we move along and you’re able to use them in real-world situations.

Histograms
A histogram is a graphical representation of the tonal data contained in an image.
It’s a very useful tool for quickly determining if a photograph is over or under exposed. Most of today’s digital cameras offer a histogram display on the LCD screen so you can check the exposure of your images while you’re shooting or immediately after the photo is taken. Although it’s often easy to tell when the exposure is wrong just by looking at the captured image, sometimes it’s not so obvious.

The human eye is capable of sensing a much wider range of light than the camera’s sensor can record. This means the camera doesn’t see things the way we do. For instance, in a high contrast scene like you might find outside on a sunny day, our eyes are capable of seeing details in both the highlight and shadow areas at the same time (unless you were to look directly into the sun or a very reflective object.) Also, our pupils can dilate or contract as needed, depending on where we’re looking.

However, since the camera “sees” with a smaller dynamic range, high contrast scenes can be challenging to shoot because it’s difficult for it to pick up details in the brightest highlight areas and the darkest shadow areas at the same time. This can result in dark, underexposed shadow areas, “blown out” overexposed highlight areas, or both.

Generally speaking, it’s easier to recover detail from underexposed areas with image processing software than it is to recover detail from overexposed areas. If you’re photographing a high contrast scene, it’s usually best to expose for the highlights and let the shadow areas fall where they may. In other words, make sure there aren’t any areas of the image that are overexposed even if it means underexposing the shadow areas.  Sometimes it’s hard to tell if an image is overexposed or not, especially if it’s only a small portion of the image. This is where the histogram display comes in.

The lines of the histogram represent the tonal data present in the image from pure black on the left side of the graph to pure white on the right. In the example below, the histogram on the left represents a good exposure. Notice that the tonal data doesn’t extend past the left or right ends of the graph. The histogram representing an underexposed image shows tonal clipping on the left side of the graph. This means that there will be dark areas in the image that are pure black with no image detail. The histogram representing an overexposed image shows tonal clipping on the right side of the graph which is the highlight area. This means there are areas of the image that are pure white or “blown out” with no image detail.

Histograms are a great tool to help you ensure you have a good exposure. However, although they’re a great guide, they shouldn’t be taken as the final word on the matter. You also have to take into account aesthetics, style, and subject. For instance, high key images are often technically overexposed but the overexposure is aesthetically correct for that style of photography.

Night photography is another area where histograms are going to be of limited use. The tonal data will usually be skewed far to the left side of the graph because photos taken at night tend to have more dark areas. If you were to try to “correct” the histogram, either by adjusting the exposure settings or with image editing software, the results might not not be very pleasing. Histograms can be useful though in determining if certain highlight areas, such as the lights of buildings in a cityscape, are overexposed.

White Balance

We can walk into a room that’s lit with a mix of daylight, fluorescent, and incandescent lighting and see practically no difference in the color of the various light sources. It all looks white to our eyes because our brains make automatic adjustments to what we see.  However, these different types of lights do have varying color temperatures that your camera, not having the benefit of the human brain, can see.

These different color temperatures can show up as color casts in your photographs if the camera’s white balance isn’t set properly. White balance is your camera’s way of compensating for different color temperatures so the light appears white or neutral. For the most part, auto white balance works pretty well outdoors but it can be easily confused when shooting indoors, especially under mixed lighting.

You’ll usually notice this more in photographs taken indoors under artificial lighting. Fluorescent lights tend to show up green and incandescent lighting tends to be very warm and creates an orange color cast.

Most digital cameras give you the option of manually setting the white balance to match the light source you’re shooting under. Some common white balance settings are daylight, cloudy, fluorescent, tungsten, and flash. Some cameras also give you the option of creating a custom white balance.

If the sample above, the image on the left has the white balance set correctly. The middle and right photos show warm and cool color casts due to incorrect settings.

Making sure the white balance is set correctly isn’t as critical if you shoot in the RAW image format because the white balance can be adjusted via editing software. If your camera doesn’t offer RAW or you prefer to shoot JPG, it’s more difficult to correct after the shot is taken.

Written by Andy on October 16, 2009 under Photography 101.

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