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One of the great advantages of digital over film photography is the ability to select your ISO on the fly. By increasing the ISO, you are able to retain reasonable shutter speeds even in low light environments. Cameras such as the Canon 10d provide ISO equivalents as high as ISO 3200. As the sensor's gain is increased to provide higher sensitivity, digital noise becomes more apparent. While the Canon 10d has little noise below ISO 800, it becomes progressively more apparent with higher settings. The newer Canon 20d has much better noise reduction built-in, reducing the work to be done in post-processing on the computer.
Even with onboard noise reduction, there will always be a need for post-processed noise reduction. In fact, it is better (although more time-consuming) to reduce noise on a computer because reduction settings can be tuned to the particular image content, rather than trying to apply the same settings across all images. Fine details (eg. natural noise-like features, such as sand, asphalt, etc.) might be mistakenly removed by an automated reduction algorithm.
There are a number of products available to reduce noise, and a quick summary is shown below.
The two most notable stand-alone solutions to noise reduction are: NeatImage and Noise Ninja. Even in the absence of a stand-alone noise-reduction tool, Photoshop itself provides some decent means of noise reduction as well.
Offering very extensive fine-grained control over the noise-reduction process, NeatImage is certainly amongst the top tools in terms of features and performance. One is also able to create a set of profiles for your particular digital camera, that can be the basis for future noise reduction work.
Trying to decide between NeatImage and NoiseNinja was difficult, as they both are well-respected tools. However, NeatImage is the only one (as of November 2004) that offers a Photoshop Plugin. This requires a purchase of their "Pro+" version, the most expensive choice, but I feel it is well worth the money. NoiseNinja had been beta-testing a Photoshop plugin over the last few months, and I believe it is now available in a released form (December 2004).
The advantages of having NeatImage integrated directly into your Photoshop workflow (as a plugin) are plentiful. In particular, one often wants to adjust noise reduction variables on a picture-by-picture basis. Noise reduction is a process that is not well suited to complete automation.
The computer has no idea what you have taken a photo of, so it cannot determine what truly is noise and what is simply texture. With our innate ability to perform advanced image recognition, we can easily recognize a pattern as being asphalt or speckled sand, whereas the computer might simply assume it to be noise. If the computer were allowed to remove these natural "noise-like" regions from photos, many textures would be destroyed, leaving a "plastic" look in its place. Therefore, it is important that the user is still involved to some degree in the reduction process.
Therefore, it is generally less desireable to apply the same degree of noise-reduction to all images, which makes a standalone batch tool less useful.
More importantly, however, is the fact that a tight integration within Photoshop allows for localized noise reduction, practically impossible with a standalone tool. Once can simply create a duplicate layer that contains the results of the noise reduction, and then apply a layer mask with opacity to blend varying degrees of reduction across the image.
It should be noted that noise reduction is a compute-intensive task, and the speed of your processor will be the deciding factor in how long you'll need to wait for the reduction tool to complete a single photo. For my test example, I am running NeatImage Pro+ on a 6 megapixel photo, shot at ISO 800 on a Canon 10d digital SLR camera (the actual file size is 2.67MB). In my tests, the initial noise "auto profile" analysis takes 8 seconds, the actual noise reduction process when applied across the entire photo takes 31 seconds. This is on a 2.5GHz AMD Athlon XP processor with 768 MB RAM. Obviously, if you are running an older or slower machine, you can expect moderate wait times.
The better noise reduction tools provide many adjustments that allow the removal of digital noise or scanner noise without losing much detail or sharpness. The example below demonstrates the "out-of-the-box" quality that is achieved with NeatImage without any tuning whatsoever (or sharpening). It should be realized that better results can be achieved with minor adjustments to the profile.
Before Noise Reduction ( 100% Crop from Canon 10d, ISO800 )
After Noise Reduction ( 100% Crop from Canon 10d, ISO800 )
Noise Removed by NeatImage ( Enhanced difference between before & after )
Workflow with the NeatImage Pro Photoshop Plugin
The first step in using the plugin is to select a layer in Photoshop and then invoke the plugin from Photoshop's Filter > Neat Image > Reduce Noise... option..
|Neat Image 4.32|
|Features:||8bit, 10 batch.||8bit, 10 batch, Plugin.||16bit, Unlm batch.||16bit, Unlm batch, Plugin.|
|Prices as of November 2004|
Photoshop CS doesn't really provide any decent built-in functionality, but a number of photoshop actions exist that perform some degree of reduction. Most notable are the actions offered by Fred Miranda. He has a series of actions that target various needs of digital photographers: noise reduction, sharpening, resizing, etc. Most of these are far better than the built-in methods provided directly from within Photoshop. It should be noted, however, that these are essentially scripts that perform numerous steps that a person could do within Photoshop, but with far more ease.