Photography News issue 24

Technique 61

Photography News Issue 24

Photo school Camera class Everyone has to start somewhere, even pros, and in Photo School we look at the core skills every beginner needs. This month, all about metering modes, and how to control exposure in Lightroom

Explained Meteringmodes

Words & pictures by Kingsley Singleton

Like foundations supporting a house, good metering is the basis of an accurate exposure. It’s the reading of the light being reflected from the subject and it lets the camera choose the appropriate exposure settings to record the scene. However, if the subject is metered poorly, over or under exposure will occur, making the picture too bright, or too dark, and you won’t get the results you’re after. Modern cameras’ metering systems should make a good reading easier than ever before. And most of the time they do. For one thing, light is measured through the lens (TTL), so that the reading is based purely your composition. In many cases, metering systems are also intelligent enough to read the subject and the type of light it’s in. So why do you sometimes still get exposures that are lighter or darker than you expected? Well, it’s not really the camera’s fault. It’s only doing what you tell it. And there’s no perfect metering mode to use all the time. Whatever camerayouhave ormode youuse, the system is basing its exposure on an assumption that the scene averages out to a mid-tone. This works fine for most subjects, but when the subject is overwhelmingly dark, or light, or there’s tricky lighting, like the sun behind the subject, it can struggle. This problem is easily fixed with exposure compensation, bracketing or using the camera’s exposure lock, or by picking a light measuringmode that better suits the subject. See right for more. The other methods we’ll be discussing in forthcoming Camera Class features.




Multi-segment metering This is the generic name for the camera’s intelligent metering. It goes by names like Evaluative (Canon), Matrix (Nikon) or ESP (Olympus) and divides the frame into segments, each assessed on its brightness. It can also take note of where you’ve focused, biasing the exposure to that area, or the subject type or colour. The segment pattern varies according to the camera.

Centre-weighted This mode biases the reading towards the middle of the frame. Therefore tones in the middle are given preference. Although exposures based on centre-weighted, can look similar to multi-segment metering, this mode is less likely to be thrown off by bright or dark areas at the edge of the frame. It’s good for portraits or backlit subjects, so long as they’re in the middle, metered area.

Spot (and partial) metering Spot metering is the most accurate mode you can use, but also the most fiddly as it’s used to measure just a small part of the frame – this can be 2-3% of the total area. Partial metering measures 10-15% of the frame. The benefit is the same; you can point the spot or partial meter at part of the frame you want to come out best – here a spot reading from the sky has silhouetted the boat.

A. Here multi-segment mode gives a lighter exposure than desired as it’s reading the whole scene and trying to balance the bright sun and the darker foreground. B. Basing its reading from the middle of the frame, here centre-weighted mode gives the best exposure, controlling the sun without the shadows getting too dark. C. Aimed at a bright point in the sky, here the spot metering mode produces a very dark exposure as it is reading very bright tones.

If you’ve metered inaccurately and need to fix an exposure in software, it can be done easily in Lightroom, and there are several ways to do it, plus safety nets to stop lightening or darkening it too much. Of course you can’t change the original metering or exposure settings, but the tones in the image can be lightened or darkened with great flexibility. Once you’ve loaded the picture into the Develop module, locate the Basic tab on the right-hand side. It’s here that global exposure changes are made to the image (global being those which affect the entire image). The slider with the greatest say in brightening or darkening the picture is Exposure. This affects the image much like raising the ISO sensitivity in camera and it runs from +5.0 to -5.0 stops, so great changes can be made. Unfortunately, just like raising the ISO in camera, if you do a lot of brightening you can see digital noise creep into the picture. Here’s how to use it along with some other useful sliders in the same tab. Software skills Controlling brightness in Lightroom

1. Use the Exposure slider Drag the Exposure slider right to lighten all of the tones in the image (or left to darken them). Note how the Histogram also moves to show how the tones are lightening (or darkening). To check you’re not ‘clipping’ the tones and losing detail, switch on the Highlights (red) and Shadows (blue) clipping warnings using the arrows at either end of the histogram.

2. Control the highlights If you see clipped highlights move the

3. Control the shadows If you see clipped shadows, move the Shadows and Blacks sliders to a positive value. As you do, the blue clipping warnings will disappear. These sliders affect only the very darkest parts of the tonal range, so you can lighten those areas of the image without changing the overall brightness of the mid- tones and highlights.

Highlights and Whites sliders to a negative value, as above. As you do, the red clipping warnings will reduce. These sliders affect only the very brightest parts of the tonal range, so you can darken those parts of the image without changing the overall brightness of the mid-tones and shadows.

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