Obliterate image noise in Photoshop: 6 easy steps
SLR technology is always improving, and one key area is the image quality of photos shot at high ISO settings. Not that long ago, shooting at anything over ISO 800 on most SLRs would result in images too noisy and degraded to be considered usable. But these days on the latest cameras, it’s possible to shoot above ISO 1600 – and even ISO 3200 – and not have to worry too much about image noise (learn when to increase ISO).
But what if you don’t have the newest SLR or have raw images with potential that are suffering from image noise? Help is at hand! By utilising the power of Adobe Camera Raw (ACR) software, it’s possible to rescue noisy raw images in a flash.
Under the Detail tab are sliders to reduce both luminance (greyscale) noise, which makes an image look grainy, and colour (chroma) noise, which is visible as coloured artefacts.
We’re using Photoshop CS5 and ACR version 6.2, which has more options under the Detail tab than previous versions, and produces better results when reducing noise in images suffering with pixels starting to ‘break up’, but the basics also apply to earlier versions of CS.
We’ll also show you how to correct the colour temperature of images that have been shot indoors under artificial lights, and how to do all your sharpening without leaving the comfort of the ACR interface.
WHAT YOU’LL NEED Photoshop CS5 or Photoshop CS6
IT ONLY TAKES 15 minutes
How to remove image noise in Photoshop
1 White balance correction
Download the noise_start.CR2 raw file in your version of Photoshop CS5 or CS6. As this track cycling photo was shot indoors under artificial lights, the white balance is a little bit off. To correct the colours here, adjust the Temperature slider to around 3750, and then drag the Tint slider down to -50 to get rid of the purple tint.
2 Raw basics
The two cycle wheels in the top-right corner are distracting, so grab the Crop tool, set mode to Normal from the drop-down menu and crop them off. To reduce the clipped highlights, set Recovery to 30. To brighten the riders and the dark Lycra, set Fill Light to 10 and set Blacks down to 0. To further lighten the cyclists, set Brightness to +60, keeping Contrast on +25.
3 Turn down the noise
First, you need to reduce the luminance noise of this image shot at ISO800. Click the Detail tab and zoom in
to 100% (Ctrl+Alt+0) so you can see the enhancements. Luminance noise is less tonally distinct than colour noise, so watch you don’t overdo noise reduction and end up blurring detail. We used the following settings: Luminance at 40, Luminance Detail at 50, leaving Luminance Contrast to 0.
4 Colour noise
Colour noise is generally more noticeable, so the ACR default colour noise reduction setting is 25, not 0. A good rule is to match the Colour noise slider with your Luminance setting, so for this image, set Colour noise to 40 and Colour Detail to 50. Experiment with your own photos as the amount of noise can change depending on the SLR, lens and exposure.
5 Clarity and vibrance
Click back on the Basics tab. Before you sharpen, adjust the Clarity slider – which adjusts midtone contrast. Set it to +20. While you’re there, set the Vibrance to +10 to boost the colours of the bicycles and clothing. The Vibrance slider minimises clipping as colours approach full saturation, by altering the saturation of lower-saturated colours without affecting the higher ones.
6 Sharpen up
Always do your sharpening last, or further editing (including resizing) can introduce ugly artefacts. On the Detail tab are several Sharpening sliders that adjust edge definition. Now the clever bit: hold down Alt as you move each slider to see which parts of the image are affected. We set Amount to 40, Radius to 1.5, Detail and Masking to 30. Don’t overdo it, as it’ll add noise. Click Save Image in the bottom-left and you’re done.
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on Sunday, July 22nd, 2012 at 1:00 pm under Photoshop Tutorials, Tutorials.
Tags: ISO sensitivity, photo editing