Photography News issue 20

Technique PHOTO SCHOOL

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Everyone has to start somewhere and in Photo School we look at the skills every beginner needs. Thismonth, how to use Auto ISO for sharper shots and control digital noise in Lightroom Camera class

Words & pictures by Kingsley Singleton

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levels, this could be fast or slow; the camera doesn’t knowwhat you want. Problems most commonly arise when a slow shutter speed is set and is too lengthy for a sharp shot. In that case you’d reset the ISO to a higher level to compensate, but this takes time and wastes opportunities, which is where Auto ISO can help. In Auto ISO mode, the camera raises or lowers sensitivity automatically, keeping the shutter speed up at a decent level. n Setting up Auto ISO To use Auto ISO, first decide on the highest ISO sensitivity you want the camera to reach. To do this, take some test shots and examine the noise produced at different levels. If you decide that, for instance, ISO 3200 is the highest you can tolerate, that’s the one to go for. Next, head into your shooting or custommenu and find the Auto ISO settings (often grouped with other ISO parameters). There you’ll be asked to set the maximum ISO setting that will be reached in Auto mode and sometimes a default or base level. On many DSLRs you’ll also get to pick a minimum shutter speed, which the camera won’t go below unless the maximum Auto ISO is reached (you’ll get a warning). Remember to turn the mode off if the light gets more predictable or you want manual control, otherwise you’ll use higher ISO settings than required.

Three settings make up a photographic exposure: shutter speed, aperture and ISO sensitivity. For best results you should take control over one or both of the first two, as this will let youmake creative decisions about the depth-of-field and/or whether any moving elements are sharp or blurred. ISO sensitivity, like film speed, is there to help you adapt to varying levels of light. So if you’re shooting in aperture-priority mode, you might manually lower the ISO to allow a longer shutter speed or raise it to allow a faster one. So how does Auto ISO fit into this? Well, it’s an automated setting that helps get good exposures in unpredictable light – like shooting a car moving in patches of sunshine and shade, or at a concert. It’s also good for keeping shutter speed at a certain level to prevent camera shake or the subject’s movement being picked up. Although in Auto ISO, you’re liable to use higher settings than you’d ideally want, the improvements in ISO performance make it a better option than ever before, and a little extra grain is better than a soft shot, so it’s worth knowing how to use it. n HowAuto ISOworks Say you’re in aperture-prioritymode andwant to shoot at f/4, the camera will take any manual ISO level you’ve set into account, then choose a shutter speed that it thinks will give a good exposure. Depending on light Software skills Clean up your pictures with Noise Reduction in Lightroom ADOBE LIGHTROOM Digital noise is something that can make or break a picture. This grain-like interference grows as ISO sensitivity is increased and can make your shots look like a blotchy mess. In-camera noise reduction (NR) can reduce grain caused by shooting at high ISOs, but often only works on JPEG files, not Raws, so if you shoot the latter, you need to know how to control interference in post-production. If you use in-camera NR, you might find it better to do it on the computer where you can tailor settings to individual pics. Noise reduction also helps if you’ve made aggressive changes to the exposure, particularly when lightening underexposed pics with lots of noise in the shadows. In Lightroom, some noise reduction is added by default, but only to colour noise, which causes red, green and blue blotches, and not luminance noise, which is often more noticeable. Here’s how it works…

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TOP Shot at 1/125sec (ISO 800) sharpness is achieved at the expense of a little extra grain. MIDDLE Shot at 1/30sec (ISO 200) the pic is smoother, but the shutter speed is too slow for a sharp shot. ABOVE LEFT & RIGHT Setting the maximum Auto ISO your camera will reach is done by accessing the ISO settings within the shooting or custommenus.

n In the Develop module, click the Detail tab to find the Noise Reduction options. If you see a ‘!’ at the top of the palette you aren’t viewing the picture at 1:1, which is required to see the effect you’re having, so zoom to 1:1 or at the top of the Detail tab use the arrow to open a 1:1 loupe. You can then use the cross hairs to pinpoint specific parts of the picture. n Under Noise Reduction move the Luminance slider right until the grain flattens out to the extent you want (hold the Alt key for a greyscale preview, which makes judging the effect easier). The Luminance Detail slider is used to retain detail and compensate for the flattening effect; a high setting will firm up the details, but at the expense of smoothness, while a low setting will soften details and compromise sharpness. Applying lots of noise reduction to high ISO images can also leave images looking washed out, which the Contrast slider compensates for; high values will retain contrast but keep more of the noise, while lower settings will look smoother, but can make the pic look flatter overall. n For removing colour noise, the Color slider controls the general amount of reduction and tends to be set to 25 by default. Take it left and you’ll see blotchy colour information return while using very high settings can make the picture look a bit washed out. Much like its counterpart for Luminance noise, the Detail slider can be used to stop the image softening, particularly around edges, but at the expense of a little more colour noise in those areas. Smoothness can help reduce any further stubborn blotches and is useful if you’ve got JPEGs saved at low quality.

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