Digital Camera World » spot metering

Creative spot metering: how professionals expose in high-contrast conditions

jmeyer — Wed, 09 Jan 2013 11:00:31 +0000

Tired of wasting pictures? Master spot metering like the pros for perfectly nailed exposures every time

Tricky lighting conditions can throw your digital camera’s metering system way off. Situations where subjects are brightly lit in darker surroundings, such as live music photography or any time there is a performer on stage, can fool evaluative/matrix metering, because it tries to produce an 18 per cent grey exposure from the whole scene.

However, spot metering takes a light reading from a small area, usually at the centre of the viewfinder or the active focus point, disregarding light from other areas in the frame.

There are two ways to get good results from spot metering. The first method of spot metering is great for subjects that are illuminated by varying lighting intensities, such as at a gig.

Simply select either aperture or shutter priority on the top dial, compose with the centre focus point over the subject and track it, always keeping the focus point fixed on the subject in the viewfinder as you shoot.

The second spot metering method provides greater compositional control, but lighting on the subject should remain constant. Switch to manual exposure mode and compose with the centre focus point fixed on the subject.

Manually align the metering bars for the best exposure. Now you can recompose the frame and zoom, retaining great subject exposure regardless of the background brightness.

How to nail exposure with spot metering in tricking conditions

01 Switch to spot metering
Most SLRs feature a dedicated spot metering button, dial or switch on the camera body or LCD panel. It’s indicated by the small dot that’s found next to the various centre-weighted and evaluative/matrix metering symbols.

02 Use manual exposure mode
You’ll get the best results by switching to manual exposure mode and placing the active centre focus point on the most important part of the frame. Line up the metering bars so that you achieve a good spot exposure.

03 Check the LCD panel
Keep an eye your rear LCD to check that you’re getting accurate exposures. Use your SLR’s histogram feature to see if there’s any pixel clipping taking place on the main subject, and readjust your metering if necessary.

Spot metering: how to find the right area within a scene

jmeyer — Mon, 09 Jul 2012 10:05:56 +0000

Spot metering mode is great for precise exposure readings, and can be a godsend when you’re shooting in tricky light. But the skill lies in deciding which part of the scene to take the reading from in the first place. Practice makes perfect, so try this exercise and see how you do…

Choose a high-contrast subject 
This picture of a lizard against a dark background is a good example, because there’s a big brightness difference. The camera doesn’t know which area needs to be correctly exposed – only you do! There are two solutions…

Set the AF point 
The first option is to select the AF point that corresponds to the part of the picture you want to be exposed correctly. Remember that the AF point is where the spot reading will be taken from. Now take the shot again but with the AF point over a different area, like the background. The exposure will be very different! For more on this, check out our camera tips for how to choose the best AF mode.

Use AE-L/AF-L 
Sometimes there won’t be an AF point in the right position for the area you want to take a spot reading from. Use the AE-L/AF-L button to lock the exposure (see our step-by-step guide on how to use AE lock to control exposure). Place the AF point over your subject, then reframe to shoot.

Compare with matrix metering 
Do either of these attempts at spot metering give better or worse exposure results? Now shoot the same high-contrast scene using matrix metering and see how the exposures differ again.

Photo tutorial: how to take a light reading using grey card

jmeyer — Thu, 16 Feb 2012 11:44:35 +0000

Everyone, of any ability, who has taken a picture with a digital camera knows that getting the tones right will make or break your image. Choosing the right part of a scene to meter from is crucial, but how do you which part of the scene is best?

When taking a light reading you want to find a midtone somewhere in the scene, or even just out of the frame. This could be light-coloured foliage, or even a Caucasian face. However, sometimes there won’t be anything around that’s the right tone for you to take a light reading. In these instances, using grey card can help you achieve perfect tones.

The traditional method of using grey card has stood the test of time. Hold your grey card in front of a subject and take a light reading from it. Sounds simple enough, right? Only there’s a little more finesse to using grey card. Below is our step-by-step guide to taking a light reading with grey card.

How to take a light reading using grey card

Step 1: Do your whites look grey?
Shoot a white subject against a white background, and your camera’s metering system will invariably give you an image that looks too dark.

Step 2: Get out the grey card
To solve this, you need to put a grey card (or something similar) where the subject is, so that it fills as much of the frame as possible.

Step 3: Lock on the target
The next step is to press the AEL (or *) button on the back of your camera so that you can take an exposure reading from the grey card.

Step 4: Back to the main feature
Now you need to remove the grey card, recompose the scene and take the picture of your white object – the whites should now look bright and clean!

Step 5: If you grey card isn’t big enough
If you are unable to fill the frame with the grey card, you may need to change your camera’s metering mode, which is located in the shooting menu.

Step 6: Spot treatment
Using spot metering means that the grey card need only occupy the very central part of the frame when you use the exposure lock.

Get better exposures

crutter — Thu, 08 Dec 2011 11:12:55 +0000

Getting your head around exposure can be daunting, so let’s start with the basics. When taking photographs, an image is recorded by light reaching your camera’s sensor. You need a certain amount of light to expose the scene correctly; too little and the image will be too dark, or under-exposed; too much and it will be too bright, or over-exposed. The amount of light reaching your sensor is controlled by three key components: aperture, shutter speed and ISO.

The aperture controls how much light is allowed through the lens – a wide aperture lets in more light, a narrow aperture less. The shutter speed determines the length of time the shutter remains open. Aperture and shutter speed work in unison to expose the image correctly, and if you adjust one you have to adjust the other: if, for example, you increase the shutter speed (therefore decreasing the length of time that light hits the sensor), then you have to use a wider aperture to let in the same amount of light to expose the shot correctly.

The other variable that affects exposure is ISO. The ISO setting affects the sensor’s sensitivity to light. The lower the ISO, the more light is required to expose the image.

Understanding exposure

To determine the aperture and shutter speed required to expose a shot correctly at a given ISO, your camera measures the amount of light reflected back from the scene using a built-in light meter. The key word here is ‘reflected’. Camera meters assume that the scene you want to photograph contains a full range of tones, and tries to expose it accordingly. This means that certain lighting conditions can confuse them – dark scenes can be over-exposed and bright scenes under-exposed – because the meter will try to expose the light or dark areas as midtones.

Dark scenes

A built-in light meter will try to produce an exposure made up of average midtones. A dark scene that’s been exposed so it’s dominated by midtones will therefore look over-exposed.

Mid-tone scenes

Scenes containing a relatively even mix of shadows, midtones and highlights, such as in the photo above, won’t give your camera’s metering system too many problems.

Bright scenes

As with dark scenes, because the built-in light meter will try to render any scene as an average midtone, very bright subjects like snow will end up looking a bit grey, rather than pure white.

How to read a histogram

You can call up the histogram on your camera’s LCD to judge the tonal distribution in a photo. The horizontal axis shows pixel brightness, ranging from pure black on the left to pure white on the right. The vertical axis shows the number of pixels at a particular brightness level.

Under-exposed

Not enough light has reached the sensor, caused by either too fast a shutter speed, too narrow an aperture, or both. This shot’s histogram is pushed all the way to the left, a situation known as ‘clipping’. If printed, the clipped areas will appear completely black, and all shadow detail will be lost.

Correctly exposed

The histogram should correspond with the tones of your scene; a dark scene should have a histogram with a bell shape on the left; a light scene should have a histogram with a bell shape on the right. For daylight scenes, expose the scene as far to the right as possible without clipping the highlights.

Over-exposed

Too much light has reached the sensor. Notice how the histogram reveals that the tonal distribution is pushed all the way to the right, and that the highlights are clipped. In the printed photo, areas of the scene that should reveal detail will appear as pure white, with no detail.

Metering modes

Multi-zone metering

This is also known as matrix, evaluative, multi-segment and pattern metering, depending on the camera you have, but all serve the same purpose. Multi-zone metering is generally the default setting on your camera when you first switch it on. In this mode, the camera divides the scene into sections and takes a reading from each section to determine an overall reading for the whole scene.

Centre-weighted metering

Centre-weighted metering also takes a reading from the whole scene, but concentrates mainly on the central 60% of the frame. It’s handy for portraits, especially when the model is in the centre of the frame. Centre-weighted metering can easily be fooled by very bright or very dark areas, but it can be easier to predict when you need to adjust the exposure than it is with the multi-zone metering mode.

Spot metering

This is the most accurate metering mode because it enables you to take a reading from a small, precise area of a scene. However, it can take a bit of practice to be able to judge precisely what constitutes a suitable midtone. To simplify matters, some photographers meter off a so-called ‘grey card’ placed in the same light source as the subject. You can pick one of these up from Jessops for around £6.

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