Hopefully after reading the first part of this blog series you’ve now got a camera and a pretty sweet lens. However, you’re probably still none the wiser as to how to take a great picture. Well, read on my friend.
The word photography comes from the Greek for ‘drawing with light’. It’s an apt name, as the most vital aspect of getting a great photograph is manipulating and capturing light in the correct way. Your camera is a chamber that needs to be filled with just the right amount of light to get the image you desire. We call that amount the exposure.
The exposure is a result of three variables: shutter speed, aperture and the brightness of your scene. Two of these, shutter speed and aperture, are controlled using your camera. Changing the shutter speed controls how long light enters the camera. Altering the aperture changes the rate at which light enters the camera.
There is an extra setting on your camera that affects exposure. It is possible to alter the sensitivity of your camera’s sensor by changing the ISO setting. By altering the ISO, you change the amount of light that you need for a given exposure. This is the equivalent of film speed that old school photographers will be familiar with. Back in the days of film, photographers had to choose a film that suited the circumstances they were shooting in. Slow films, such as ISO 50, used small blobs of photographic emulsion. When these reacted to light, they would produce a photograph with very little visible ‘grain’. These slow films required a lot of light to expose properly. Faster films needed less light but used larger blobs of emulsion that produced a very visible grain. Film photographers were often constrained by the film they were working with.
The digital photographer has the luxury of being able to set ISO sensitivity at the press of a button to adapt to changing conditions. Your camera achieves this by amplifying the light signal received by the sensor. Unfortunately, this will also boost the electrical interference naturally generated by the sensor. This is called ‘noise.’ It manifests itself much the same as the grain on film. Your camera’s lowest ISO will generally be 100. This will produce the cleanest result. However, lower ISO settings require more light to achieve the same exposure as higher settings.
Take, for instance, an image taken on a sunny day at an aperture of F4. You set your camera to the lowest ISO which is 100. You now need a shutter speed of 1/1600s for the correct exposure. This is fine as you want to freeze movement. In the evening you want to use the same aperture of F4. To expose the image properly at ISO 100 you need to leave the shutter open for 30s. This is too long to hand-hold the camera, so you must increase the ISO in order to allow you to use a shutter speed of at least 1/60s.
Shooting in dimly lit rooms is a situation that almost every photographer has encountered. If you are shooting inside a dark room or at night you will need to use a higher ISO. It is generally preferable to keep the ISO as low as you can whilst still getting the correct exposure. If it’s practical, and if you aren’t concerned with freezing a moving subject, then it’s generally preferable to use a tripod and keep the ISO low. Low ISO numbers such as 100 provide better fine detail and less distracting digital ‘noise’ than higher numbers such as 1000. Some modern cameras have ISOs as high as 25,600 but you may find images at these settings too noisy for your needs.
Your camera has several modes to control exposure, normally available via a dial on the left hand side of the top cover. These will be usually be given the names Auto, Av, Tv, P and M.
Automatic for the People
Inside your camera is a very sophisticated processor that enables it to choose from a selection of settings for a multitude of common scenarios. These have been programmed into your camera based on the subjects that people most often take pictures of.
The Auto setting uses this processor to control all of your camera’s settings. Auto is usually designated by a green square on the mode dial. In the Auto mode, your camera will review the scene and set everything automatically. The shutter speed, aperture, ISO, white balance, light metering and autofocus settings are all controlled by the camera in Auto mode.
What your camera can’t do is read your mind. Neither can it make artistic decisions. Say you are photographing a person in front of a window. You want a nice artistic looking silhouette with the camera exposing for the light coming through the window. The camera assumes you want to expose the image so that the subject’s face is visible. The result? Your image is overexposed. By relying on the Auto modes and relinquishing complete control to your camera, you are limiting the creative potential of your images. For these reasons Auto is rarely a suitable mode for professional looking business photography.
A is for Aperture
Av stands for aperture value, and this mode is often called aperture priority. In Av mode, you set the aperture and ISO you want to work with. The camera calculates what shutter speed will give the correct exposure. This is great when your subject is stationary and you want to have complete control over the depth of field in your image.
The term depth of field refers to the size of the area that’s in focus in an image. Large apertures such as f2.8 or f1.4 create a shallow depth of field. People associate this effect with better quality photography. (Remember, f-numbers are the wrong way around. A low f-number equals a large aperture!) You can use a shallow depth of field to draw attention to your subject by blurring out distracting details in the background. It is hard to produce shallow depth of field with point and shoot cameras or cheaper SLR lenses.
As a rule, apertures of around f2.8 or below are good for picking out details like those in the above image. Taking pictures with your lens at it’s widest aperture in this way is called using it ‘wide open’. It’s worth noting that most lenses will not achieve their optimum image quality when used wide open. To get the best results from your lens, it’s worth using it two stops down from maximum aperture. However, this is largely theoretical and most photographers will frequently use lenses wide open.
Smaller apertures, such as f11 or f16, provide a much deeper depth of field. A deeper depth of field means that both near and distant objects will be in focus. Using your lens in this way allows you to keep much more of the image in focus. This is useful when you are photographing groups of people or taking wide shots of landscapes and buildings. Be aware that above f16 the image quality will degrade in most lenses. For that reason it’s best to avoid extremely small apertures such as f22.
Those are the basics of controlling depth of field using lens aperture. If you want to read more about using depth of field, including the effects of focal length, then check out this article by Digital Camera World.
Tv stands for time value. This mode is often called shutter priority. In shutter priority mode, you set the shutter speed and ISO and the camera decides which aperture will provide the right exposure.
This mode is useful if you’re photographing a moving subject – whether you want to freeze something in time or create an artistic blur. When you’re trying to capture movement, selecting the right shutter speed is crucial.
Shutter speed is measured in seconds and fractions of a second. The shutter speeds used in cameras are standardised so that each change, called a stop, either doubles or halves the amount of light entering the camera. This means that 1/60 s lets in half the light of 1/30 s but double that of 1/125 s.This might sound complicated, but it’s really not. We’ll look at how this works in the section on the Manual mode later on.
Most of your time behind the camera will be trying to capture subjects frozen in time with no noticeable blur. An example of this would be trying to capture a candid shot of people mingling at an event. To do this, you need to use a shutter speed that is at least fast enough avoid camera shake and also able to freeze your subject.
Selecting a fast enough shutter speed to prevent camera shake from ruining your images is easy to do. Camera shake occurs because of the movement that your hands make as you are taking a picture. If you use too slow a shutter speed, this movement manifests as blur in your images.
The key to getting sharp images is to use a shutter speed numerically equal to or faster than the focal length of your lens. As an example, if you were to take a picture with a 50mm lens you would need to select a shutter speed of 1/60 s. The lowest speed you can use handheld with no image stabilisation technology would be 1/30 s using a 24mm lens. Some lenses with image stabilisation technology will allow you to use a shutter speed up to four stops below the normal recommended minimum. It’s worth remembering that whilst image stabilisation can prevent camera shake, it won’t freeze movement.
Once you’ve set your lowest usable shutter speed, you can then move to a higher shutter speed to suit your subject. As long as you time your shots well, you could get good images of attendees at an event with a shutter speed of 1/60 s or 1/125 s.
By placing your camera on a tripod and using a slow shutter speed, you add movement to a scene that would otherwise look mundane. Long exposures of several seconds can provide a fresh perspective on an everyday occurrence. Scenes such as employees moving around an office take on another dimension when captured in this way. This is a good way of emphasising the passage of time and portraying travel. When using such a low shutter speed the camera will set a small aperture to prevent overexposure. Make sure you place your camera on a tripod so that only the moving parts of your image are blurred.
Get with the Program
Program mode is your best first step if you’re keen to break away from the constraints of the Auto mode. Like Auto mode, Program mode will choose the aperture and shutter speed for you. The difference is that Program mode will allow you to make other changes, such as white balance and ISO, yourself.
Most cameras will give you some flexibility in the exposure by allowing Program Shift. This locks the exposure but allows you to shift the value of either the shutter speed or the aperture. The camera will then alter the other setting accordingly.
It’s important to realise that, like Auto, Program mode will expose your image in the way the camera believes is ideal in the situation. The camera won’t let you under or over expose your image for artistic effect. You will also find it difficult to control both depth of field and shutter speed at the same time, because the camera links the aperture and shutter settings.
The only option when you want complete control over your camera is to switch to Manual mode.
Read the Manual
Experienced photographers will often control exposure themselves using the Manual mode on their cameras. This mode gives you complete artistic control over the shutter speed and aperture. On modern digital cameras it is possible to use this mode in conjunction with the Auto ISO setting to give you greater control over your images while still allowing your camera to calculate the correct exposure.
Remember how the shutter speed doubles or halves as we go up or down a stop? Well, the f -numbers we use to describe aperture work in a similar way. Each time you go up one f-number, such as from f2.8 to f4, the amount of light entering the camera is halved. This standardisation allows you to maintain the same exposure whilst making changes to aperture and shutter speed. and it’s key to getting the most out of the Manual mode.
Let’s say, for example, that you are photographing an event. You have your camera set at f4 and 1/60 s and are happy with the exposure. You also have your camera set to ISO 100 for the best image quality. You check some of your shots your camera’s LCD and notice you’re getting some motion blur as people move. You decide to up your shutter speed to 1/125 s to stop this blur but you want to maintain the same exposure. To compensate for this increase in shutter speed (which has halved the amount of light entering the camera) you must now increase your aperture from f4 to f2.8 (which doubles the amount of light entering the camera). Your other choice, if you want to maintain your depth of field, is to leave your aperture at f4 and increase your camera’s sensitivity one stop to ISO 200. This would double the sensitivity of the camera’s sensor. If you have an auto ISO setting on your camera this would automatically alter the ISO value to compensate for the change in shutter speed.
The value of the Manual mode lies in the control it provides you. Unlike the other shooting modes above the Manual mode allows you to control both depth of field and shutter speed independently. It takes more practice and more skill to use your camera in this way but in difficult shooting situations like those described above it is often the best option.