Welcome to the new season and especially to the new members and guests, visiting for the first time.
The beginners subject tonight was Opening, Viewing and Saving Files. I am still recommending XnView as an excellent free general-purpose image viewer for all operating systems. Any recent version of Photoshop Elements (or Photoshop CS if you're feeling rich) is also essential to benefit from the shared experience of all our members.
Beginners should set their cameras to sRGB colour space (not Adobe RGB), JPG highest quality (not Raw) and turn off Auto ISO.
IMAGE NOISE
Noise in digital images appears as small coloured speckles and can be a problem especially with compact cameras in low light conditions and when the ISO/film speed setting is high.
Camera sensors always produce a small amount of random electrical information but this is normally drowned out by the strong signal generated by light from the subject. However, when the light levels are low, the genuine and the random signals become similar in size and the image is subject to visible noise. The smaller the sensor, the bigger the problem. The latest full-frame SLRs are almost noise-free and this technology will be seen on affordable cameras within the next few years.
In the meantime, the problem can be minimised by trying to get more light on darker subjects and avoiding high ISO settings - especially the auto ISO camera setting which will choose high ISO in preference to low shutter speed, and then use a tripod if necessary. Unfortunately, long exposures can also produce noise so it's all a bit of a compromise.
NOISE REDUCTION
Having got noise in an image, what can we do about it? In Photoshop/Elements try Filter>Noise>Reduce Noise. The Reduce Colour Noise slider will remove the coloured speckles and the Strength slider will reduce much of the remaining noise. You will need to zoom in to 100% or more to see the effect. Over-doing the Strength slider will result in smearing of the image and loss of detail.
Greater noise-reduction can be achieved via the Adobe Camera Raw (ACR) interface. For a noisy JPG, go to File>Open As and then navigate to the required JPG and choose Open As>Camera Raw. In the resulting ACR screen, choose the Detail tab and adjust the Luminance and Colour sliders to reduce the noise. Note that noise reduction needs to be balanced against sharpening on the same screen, which tends to have the opposite effect! This same ACR procedure gives even better results from a Raw original image.
Adobe Camera Raw is currently at version 6.2 (October 2010) This version has markedly improved noise reduction over the previous version 5.6. If you have Photoshop CS5 you will already have ACR 6.2. However if you have Elements 8 you will need to update ACR manually from the Adobe ACR website here. This may also apply to Elements 9.
There are many commercial solutions to noise reduction, such as Noise Ninja ($45) , NoiseWare ($50) and Topaz Denoise ($80) I trialled the latter two which are highly rated and found that the results, for me, were broadly equivalent to those from ACR6.2 so I will not be investing in these products myself.
Images sometimes have to be reduced in pixel dimensions eg for Projected Digital Image competitions and I tried noise reduction before re-sizing and vice-versa. Surprisingly, the results were similar.
ADDING NOISE
Noise is not necessarily a bad thing. In the pre-digital age, fast films were often sought-after for their grainy atmospheric quality which suited certain types of image.
Noise or Grain can be added to an image in a variety of ways for creative effect;
Filter>Noise>Add Noise
Filter>Texture>Grain
Filter>Artistic>Film Grain
NEXT MEETING
Thursday 4th November 2010 at 7:30pm in the Small Barn Hall, Amersham Community Centre.
Cheers, Steve Brabner