Are your images noisy?
Author: weshoot
Digital images have a problem not seen in film. Digital images can have “noise.” For a definition of noise, I will refer you to Wikipedia at: http://en.wikipedia.org/wiki/Image_noise . Someone on the ‘net said that noise in digital images was like grain in film. I don’t think so. While grain in film was largely ISO or ASA dependent – lower grain at numerically lower ISO (ASA) numbers – noise seems to come from factors such as underexposure, quality of the sensor, how many megapixels are jammed onto the sensor, etc. Grain happened all over the image, while noise seems to come up in areas of a digital image that are underexposed. In my experience noise can take two forms: color and luminance. Luminance is a somewhat grainy appearance and usually makes shadows appear to have dark mottled areas. Color noise is grainy, mottled, and sometimes adds colors like yellow and green to the mix. Even relatively good cameras at low ISO numbers can have some noise in the shadow areas, especially when trying to lighten them up. Some of the ways to deal with noise are: get a low-noise camera; overexpose a little; shoot raw images, which have more latitude for correction than jpegs; use noiseware software; darken shadow areas so the noise is blended; blur the shadow noise so it is not mottled; color or clone in noisy areas.
Noiseware, such as that made by Imagenomic, or Noise Ninja, etc., use algorithms to alleviate noise. But be warned, the heavier you use such software, the softer the image will look in the areas covered by the software. In other words, if you use the software on the entire image, it may appear soft or blurred. One can use editing software to section off areas of an image and only use the software on those areas. I do it a different way.
I open the image in Photoshop and create a duplicate layer of the image. I go to the bottom layer and use my noiseware plugin filter to smooth the noise on the entire layer. I move up to the upper layer, and create a mask on that layer. While in that mask, I simply use black to paint out the areas in the upper layer and let the lower noisewared layer show through. This gets rid of the noise only where I want, and does not blur the rest of the image, which still is absolutely sharp.
Some clients do not mind noise, while others, notably the stock agencies, abhor noise and will fail an image for noise, or Soft Or Lacking Definition (SOLD) images as quick as you would blink. Try to eliminate noise in your photos for a better look, and better images.
– Gary Silverstein
Tags: artifact, correct, correction, digital noise, layer, mask, masking, noise, Photoshop
August 2nd, 2010 at 2:20 pm
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