Metering. What is it? What does it mean?

Whether people who are viewing your work know anything about photography or not, exposure is important.

It is up to you as the photographer to make sure you produce correctly exposed images time after time and not just shoot and hope for the best.  This is probably one of the more difficult for someone just beginning in photography to understand and get a compete grasp on.  This is where metering comes in.

Keeping it basic – metering refers to the process whereby the built in light meter in a camera determines, based on the amount of light reflecting off your subject, how to expose the image.  This is all fine in a world where all photographic subjects reflects the same amount of light but this is not quite the case.  Different surfaces reflect light in different ways and most cameras will try and even out the various degree of lighting in order to deliver an ‘average’ exposure.  This might not be such a bad thing if you have an even spread of objects, dark to light, in your frame.  It will however lead to unexpected and disappointing results if you are faced with an image which is heavily occupied by purely light or dark images.

Most DSLR cameras have various metering modes which allows you, as the photographer, to guide the camera as to how the image should be exposed.

The three main metering options are:

• Matrix Metering Mode(Nikon) or Evaluative Metering Mode (Canon)
• Centre-Weighted Metering Mode
• Spot Metering Mode(Nikon) or Partial Metering Mode (Canon)

Each of the above metering options functions by assigning a weighting to different regions of your frame where the areas with higher weight is considered more reliable and will then play a more important role in the final exposure of your image.

Matrix Metering

This type of metering tells the camera to average the exposure over almost the entire viewfinder frame.  It is recommended by most camera manufacturers for all round photography and probably what most beginners will use when starting out.

The image on the right shows the coverage area in black that will get used during Matrix or Evaluative Metering.

For wildlife and nature photography this is the kind of metering you will probably use for all round shooting until you are faced with a scene where you have a large contrast of textures and colours in your frame.  At this point you will have to decide what the focal point of your image is going to be and expose for that specific area of the image.

You must however be aware that this type of metering can be quite unpredictable as the camera’s built in light meter will do all the necessary calculations in order to produce the ‘correct’ exposure.  If you want more control and more predictable outcomes you should start working with centre-weighted metering.

Centre-Weighted Metering

During this type of metering the whole frame gets used by the camera to determine perfect exposure but preference is given to the centre of the frame – as seen on the right.

Initially this type of metering, along with Spot Metering, might be more difficult to use but it will give the photographer a lot more control over the exposure of the image.  This kind of metering is ideal for close up portraits of animals and bird photography as the centre area, where your focal point will be, will be the area which the camera uses to determine the exposure for the image.

For example, if you are trying to photography a bird with strong back lighting your camera will, if you are using matrix metering, average out the scene and underexpose the entire image to compensate for the bright background.  This will result in your focal area, the bird, being underexposed and rendered as a silhouette.  By using centre-weighted metering you can make sure your focal areas is exposed correctly.

Spot Metering

During this type of metering the camera takes a very small area, around 2% of the entire frame, and uses this area to calculate exposure.

This type of metering takes centre-weighted metering a little further in that the photographer can be a lot more specific with which critical areas need to be used by the camera when exposing the image.  Both centre-weighted and spot metering can be extremely useful when you are trying to create interesting exposures, when the you are faced with unusual ambient light and and when you shoot sunset and sunrise landscapes.

You must remember that cameras, however ‘clever’ they are becoming, still cannot match the human eye and creative insight the photographer brings to the art of photography.  When you, as the photographer, overrides the camera’s determined exposure you can use the exposure compensation on the camera to alter the exposure to suit your desired outcome.  As you progress with your own photography this is something you will feel more and more comfortable with.

I personally always keep my camera set to centre-weighted metering as this gives me the freedom to guide the camera toward exposing for my focal point.  During the last few minutes of sun light, when the light is changing all the time I might switch to matrix metering but this will of course be determined by what the subject is and what exactly I am trying to do with the image.

Example 1 – Matrix Metering

Nikon D300, Sigma 28-200 @ 100mm, 1/400, f/5.6, ISO 400, Matrix Metering

In the above example I was flat on the floor at the Johannesburg Botanical Gardens as I was taking pictures of Ziggy, one of my two new 12 week old Boston Terrier puppies.

After a few trial runs I was happy to go with matrix metering as I saw that by filling the frame with Ziggy and the grass there were no excessively dark or light areas in the scene and that the camera would probably get close to what I would consider good exposure for this shot.  Overall the entire frame is well exposed except for the very tiny area on the front left foot.  This is however not sufficient to detract from the scene and the camera’s matrix mode did a pretty good job on this one.

Example 2 – Centre-Weighted Metering

Nikon D300, Sigma 28-200 @ 150mm, 1/320, f/5.6, ISO 400, Centre-Weighted Metering

The above image of my sister’s new 4 month old bulldog was taken using centre-weighted metering.  As ‘Seun’ was running the same path all the time, chasing other dogs, I new more or less where he would be passing.

The problem was that the trees in the background were not uniform and every couple of meters the trees would break to leave a gap where the strong late afternoon light made for a very difficult exposure problem as I panned along with his movement and the ever changing background light.

I was lucky that the background behind the trees ended up begin quite small due to where I took the shot but better safe than sorry and by using centre-weighted metering I was able to make sure that ‘Seun’ was properly exposed as he was the obvious focal point of the image.  I guess that is the end of a very basic look at metering and how you could use it when planning the exposure of your images.  If you have any thoughts, comments or questions please don’t hesitate to contact me.

As you can see from the above examples I am currently in Johannesburg and have been spending quite a bit of time with a different kind of wildlife.  Adele and I are currently on leave and will be taking our two new boys, Ziggy and Rocky to the Vaal River for a few days worth of rest and relaxation.  Looking forward to kicking back and perhaps getting a few nice river sunsets and sunrises.

Will be back later this week with the Weekly High Five which should prove to be a difficult one to choose as there have bene more than a hundrednew images uploaded during the last few days.  Make sure to visit the Photo-Africa Stock Library to view some great African Wildlife & Nature image.

As always I look forward to hearing from you.

Until next time.

Gerry