Technique PHOTO SCHOOL
Everyone has to start somewhere, even top pros, and in our regular Photo School feature we’re taking a close look at core techniques that every beginner needs to know. This month, in Camera class we look at how to counter the effects of digital noise fromhigh ISO sensitivities, while Software skills demonstrates how to reduce noise in Lightroom
Words by Ian Fyfe
Using a high ISO sensitivity is often unavoidable, and this can create digital noise that impacts on image quality. All is not lost though – here we look in detail at noise and how to minimise its effects. n What is digital noise? Things like electrical interference, heat and sensor imperfections produce background electrical signals in a camera’s sensor. When there’s plenty of light and the ISO sensitivity is low, these signals are unnoticeable compared to the much stronger ones caused by light. However, when there’s little light and ISO sensitivity is increased, they become much bigger relative to the light-induced signals and interfere with images by creating digital noise – this appears as a combination of monochromatic and coloured speckling. n Can I prevent digital noise? Without doubt, prevention is better than cure, so it’s best to do what you can at the capture stage. This generally means keeping the ISO sensitivity as low as possible, but you can also improve things by making sure you don’t underexpose. Digital noise is Software skills Part 7: Reducing digital noise ADOBE LIGHTROOM Shoot at high ISOs and your images can suffer from digital noise, a grainy, mottled effect that can look horrible in areas of even tone or shadow. Noise also turns fine detail mushy looking. It’s true to say that the latest cameras suffer from noise less than those of a few years ago. A new DSLR shoots at ISO 1000 or more without much noise. However, cameras of a few years ago, even high-end models, can suffer badly. Software like Lightroom can help keep noise to acceptable levels. There are two types of noise: luminance and colour. Both increase as ISO increases, and are more evident in low light. Luminance looks like film grain, while colour is splotches of colour, often red and green. Both types vary depending on the camera. This image was taken at ISO 6400 on a Nikon D800 fitted with a 16-35mm zoom lens. Words by Will Cheung
n Is there anything I can do without software? If you don’t have software, or don’t want to spend time processing Raw files, turn on the camera’s high ISO noise reduction. This applies noise reduction (NR) to JPEGs only at the time of capture, and you can usually select the extent of noise reduction to suit the amount of noise. Results vary between manufacturers and cameras, but you generally need to be careful because the processing can further impact on image quality. Experiment to find a level that has an effect without overdoing it. Usually, you can shoot Raw alongside JPEGs with NR turned on, so if you’re not happy with the camera’s processing, you can turn to the Raw and do it yourself.
worst in dark areas, so if you need to lift shadows in post-processing, you risk accentuating the noise. It’s better to err on the side of slight overexposure to avoid shadows that need lightening. n Can I reduce digital noise once it’s there? If a high ISO, and therefore noise, is unavoidable, the best way to deal with it is shooting Raw and reducing noise in software post-capture. Adobe Lightroom does a fantastic job of this (see how in Software Skills below), but there are plenty of other good options – onOne Perfect Photo Suite, Corel PaintShop Pro and Noise Ninja to name a few, as well as your camera manufacturer’s supplied software.
NEXTMONTH: All you need to know about white- balance, in-camera and in software
STEP 1 Go to the Detail panel of the Develop module and click on the ‘switch’ in the top left corner to make the controls active – the feature is inactive if the words are greyed out. To make sure you are at the software’s default settings, hold down Alt or Option and the reset option is displayed.
STEP 2 Click on the black arrow to open a preview window. Click on the preview image and it zooms in to 100% or zooms out. It’s easier to see what is going on by displaying the image at 100% (minimum) in the main window. If you close the preview window, an exclamation mark shows in the top left. Click on this to show the image at 100%.
BEFORE Noise reduction at zero in Lightroom 5
STEP 4 The Luminance default is zero and 50 for its Detail. If your image looks grainy don’t go too far with Luminance because fine detail suffers – moving the Detail slider right minimises this.
STEP 3 The default for Color noise is 25. If your image has coloured grain increase this value. The default for its Detail is 50 but if moving the Color slider loses details move Detail to the right.
AFTER Using Luminance and Color NR in Lightroom
Photography News | Issue 7
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