Photo noise reduction

15th November - 2001
By Ian Burley

Noise reduction for digital photos? It sounds as if Dolby is getting into the imaging market. Not quite – but a company that offers an interesting solution for reducing noise in digital photos is Ottowa-based Holographic Technologies, which offers its Photo-Sampler product.

Noise in digital photos is characterised by randomly coloured and often intrusive pixels that stand out from more uniform detail in an image. It can give an image a grainy or sandy effect that can ruin delicate tones and highlights. A sign of a good digital camera is images that lack noise. However, if you are forced to use a higher ISO (light sensitivity) setting on your camera, or shoot in low light conditions, noise will almost inevitably be the price you have to pay. Some cameras now incorporate noise reduction, but it’s still a relatively rare feature.

There are software processes that can treat noise in an image, but usually at the expense of image sharpness and clarity. Some of the latest cameras from companies like Sony and Olympus offer in-camera noise reduction that works by comparing two separate snaps of the scene and subtracting the random noise pixels that don’t occur in both versions of the image. It couldn’t be simpler.

But what if you don’t have a clever noise-reducing camera? Photo-Sampler works in a similar way. It uses the same comparison process, called the ‘differential processor’ by Holographic Technologies. This analyses two or more separate images taken of the subject and filters out data that isn’t common to all the images. That data is almost certainly noise.

The main problem with Photo-Sampler is that for best results it needs static subjects. That means the subject images to be compared need to be almost perfectly framed, which could require a tripod mounted camera, for example.

We haven’t tried Photo-Sampler yet, but it sounds promising and there is a free demo version of the software available by download from Holographic Technologies’ Web site. Two versions of the software are available: Lite, priced US$39.95 (about £29) and Professional, priced US$74.95 (about £54).
 

Holographic Technologies Web site

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