Beginners Guide: How to Use the Metering Systems on Your Digital Camera
Digital cameras use sophisticated metering systems to decide how much light there is in a scene.
This post explains the basics of how to use the three types of metering systems found on most digital cameras: 3-D Matrix metering, Centre-weighted metering and Spot metering.
3-D Matrix metering (also called Evaluative metering)
What is Matrix Metering?
The camera sets the exposure automatically to suit the scene, taking into consideration both dark and light area’s.
The majority of digital cameras offer a sophisticated metering system that is divided up into tiny segments. Each segment is analyzed individually and the results compared to a database of thousands of scenes stored in the camera’s processor. This helps the camera identify which kind of scene has been photographed and provide an appropriate exposure. This system works extremely well under most lighting situations.
How does it work?
Matrix metering works by dividing the frame into several small zones and taking separate light readings from each one. The camera then guesses which parts of the scene are important and exposes accordingly. For the most part, it does a pretty good job at picking the correct exposure.
When should I use it?
Matrix metering is good for evenly backlit subjects like portraiture and landscapes. It’s also the best one to use when you’re not sure which metering mode to use.
Centre-Weighted Metering
Many digital cameras offer a centre-weighted metering option for setting the correct exposure for a scene. This metering system gives more emphasis to the brightness of light in the centre of the frame, where, as with the focus, the main subject is assumed to be. Using the centre-weighted metering method takes a little practice to get right. It is also prone to being fooled by off-centre subjects or large areas of extreme light or dark.
Center weighted metering would be effective when you have a bright background or backlit subject. For example, if you were taking a photograph of a persons face on a sunny day at the beach. You wouldn’t want the strong background light, or the white sand, to effect the exposure on their face. As long as the persons face was correctly exposed, that’s all that matters. It’s times like this, you would choose center weighted metering.
Spot-Metering
Some digital cameras also offer the spot-metering method of exposure calculation. In this method the camera measures the brightness of a tiny area at the centre of the frame and uses that to set the exposure. Spot-metering requires practice to master. It offers the photographer great flexiblilty in measuring the exposure in a scene.
Spot (Nikon) or Partial (Canon) metering should be used when you want to take an exposure reading on a specific area. It takes the reading from a very small area in the middle of your composition.
![[Post to Twitter]](http://fotoeire.com/wordpress/wp-content/plugins/tweet-this/tweet-this-small.png)
Tweet ThisBeginners Guide: Understanding ISO
ISO is a measure of how sensitive your camera’s sensor (CCD) is to light. The higher the ISO number the more sensitive the sensor is, and therefore the lower the amount of light needed to make an acceptable picture.
Using a higher ISO setting on your camera will allow you to take pictures in lower light. In this way, you can take pictures in lower light without needing long exposures, which would otherwise result in camera shake.
There are two reasons for having the option to change the ISO setting on your digital camera:
1. Versatility
High sensitivity means you need very little light to get the right exposure for your picture. This means you can adopt a range of creative techniques, such as shallow depth of field by using a very wide aperture, or using long exposures to capture motion or increase the effect of blur.
2. Image quality
Digital camera sensors (CCDs) are not very sensitive to light. Most have an optimum ISO setting of ISO 100 or even less. The higher ISO setting is achieved through amplification of the digital signal after the picture has been taken. Consequently, the more you amplify the signal the more noise you get in the final image. This also means the camera’s processor has to use Noise Reduction software to smooth things out. Together noise and noise reduction have a detrimental effect on the image quality (sharpness and colour) as ISO increases.
Using ISO
The default setting on most cameras is auto ISO, where the camera sets the ISO according to the brightness of the scene. Low ISO settings (which offer the very best quality) are used wherever possible, with the sensitivity only increasing where there would otherwise be a risk of camera shake. This is fine for most everyday ‘point and shoot’ photography. You can, however, change the ISO setting manually, and it’s worth getting to grips with this so you, rather than the camera, can make the decision.
ISO 50-100
Use for bright days when you want the best possible quality. Unless you’re shooting with a very long lens you won’t need anything higher in fine weather. You can also use a low ISO setting at night when you want a long exposure (such as when capturing the blur of car headlight trails or shooting fireworks). In such cases you’ll need a tripod to avoid camera shake.
ISO 100-400
Ideal outdoors on overcast days or when using a long lens in bright weather. ISO 200 is often the highest setting you can use without risking noise in your image.
ISO 400-800
For shooting in low light, with a very long zoom or when trying to freeze fast action. ISO 400 is when noise first starts to become a problem, but it’s usually preferable to have a bit of noise than the blur of camera shake
ISO 800-1600
For shooting handheld at night, indoors without flash and in any situation where a lower ISO would cause blur through camera shake or subject motion. Noise is unavoidable at ISO 800 and higher (and most cameras don’t even offer the option).
ISO 1600-3200
Higher ISO settings can also be used to extend the range of your on-camera flash, and to allow even more flexibility in low light (by turning off the flash entirely).
Quick Tips:
- Use a low ISO when taking pictures in good light. This will result in better quality images.
- If you are taking pictures in low light or indoors, you can use a high ISO setting.
- To freeze action or movement, use a high ISO setting. This allows you to use faster shutter speeds.
Beginners Guide: Choosing Shutter Speeds
The ability to control the duration of an exposure is an incredibly powerful tool for the photographer. Most digital cameras allow you to adjust the shutter speed from several seconds to up to 1/10,000 of a second. In this ‘bytesize’ post I shall introduce you to three of the main factors involved in choosing a shutter speed:
- avoiding camera shake;
- controlling the amount of light entering the camera;
- freezing movement in an image.
Avoiding Camera Shake
If the shutter speed is set too low, your image will show signs of camera shake. There will be an overall blurring of the whole image. This can occur as a result of anything from the zoom setting used, to the size, shape and weight of the camera, to the steadiness of your own hands. As a rule, you can avoid camera shake by using a shutter speed slightly greater than the focal length of the lens being used. In other words, if you are using a 35-200mm lens you will need to use a minimum of 1/40 second at the wide-angle end of the lens and a minimum of 1/250 second at the telephoto end of the lens. Most cameras display the shutter speed on the LCD screen and in the camera’s menu system. It may sometimes be displayed without the top part of the fraction (’1/’), so 1/250 of a second would be displayed as 250.
Controlling Light
Longer shutter speeds let more light into the camera. Reducing the shutter speed is one way of allowing you to shoot in dark environments. When photographing indoors, for example, you can decrease the shutter speed to let in more light. Also, when photographing at night you will need to use a very slow shutter speed. However, you will also need to support the camera on a tripod to avoid camera shake.
Freezing Movement
Faster shutter speeds can ‘freeze’ movement. Slow shutter speeds can ‘blur’ movement. This is a powerful technique for conveying a sense of action in a photograph. While photographs taken with fast shutter speeds can be taken with the camera handheld, it is important that the camera is supported on a tripod when using slow shutter speeds.
As a rule if you are going to hand hold a compact digital camera you will need to use a shutter speed of about 1/40 of a second at the wide end of a zoom lens to avoid camera shake. You will need a shutter speed of 1/125 of a second when using the long end of a 3x zoom and a shutter speed of 1/300 of a second when using the long end of a 6x zoom lens. If you are going to use shutter speeds slower than this you will need to support your camera on a tripod in order to avoid blurr and get sharp images.
Quick Tips:
- A fast shutter speed freezes movement, a slow shutter speed enhances blur.
- Putting your camera on a tripod and using a long exposure (slow shutter speed) will allow you to capture the movement of water in a waterfall.
- An exposure of 2 or 3 seconds will allow you to capture the trailing lights of cars at night.
- Panning the camera with a moving person or car will allow you to use a slower shutter speed (eg.1/30 second) and still get a sharp image.
- Putting the camera on a tripod and using a slow shutter speed will allow you to capture a sense of movement in a scene.
‘ByteSize’ Guide to Digital Photography
Over the next few months I shall be posting a series of ‘bite-size’ tips to help you get the most out of your digital camera. From photographing people, buildings and landscapes to how to use colour and different types of light sources.
Each ‘Bytesize’ post will introduce you to some of the basic techniques photographers use to create visually stunning images. I will discuss some of the fundamentals of digital photography, such as exposure, ISO and white balance, and look at the main photographic subjects.
You will also find suggestions on the best equipment and accessories for the job, plus top tips and step-by-step guides on how to get the best out of your compact digital camera or DSLR.
Topics will include:
- How to Photograph People
- How to Photograph Buildings
- How to Photograph Landscapes
- Using Natural Light
- Using Colour
- How to Compose an Image
- Choosing Shutter Speeds
- Understanding ISO
- How to Use the Metering Systems on Your Digital Camera
Think of this as your own personal user’s guidebook filled with ideas and techniques which will help you put the creativity into your photography.
Thanks for dropping by.
Did you like this? If so, please bookmark it,
