Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: MarkBarbieri on February 08, 2010, 08:52:43 pm
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Is there software that takes a stack of images and combines them for the purpose of noise reduction?
I'm thinking about situations where I don't have a tripod and the light levels are too low for handholding at a decent ISO. A single shot take at a high ISO would be noisy. If I took many shots, a computer could align the images and then compare them to assist with noise reduction. Is there software that already does this?
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PhotoAcute does this.
photoacute.com
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Is there software that takes a stack of images and combines them for the purpose of noise reduction?
There is software for astronomy purposes that does it. That software usually does it on linear gamma image data to be most effective, but gamma corrected images also benefit. You can also do it (within limits) by layering images in Photoshop, as described here (http://www.cambridgeincolour.com/techniques/image-averaging-noise.htm).
Cheers,
Bart
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The Extended version of Photoshop allows image stacking for achieving noise reduction. I believe it is a little more automated than the procedure that Bart linked to but you have to shell out the extra bucks for the extended version. It wouldn´t be worth it to me unless I was also interested in the other Extended features like 3D. Also, it´s worth mentioning that I´m pretty sure that once you go with PS Extended, Adobe won´t let you upgrade in the future to regular PS - you have to upgrade to the new version of PS Extended.
Another thing you might want to take a look at is Guillermo Lujik´s Zero Noise program. I have not tried it yet but it looks pretty cool. The link is in Spanish but Google Translate does a pretty good job. The program controls are in English. Here is the link:
http://www.guillermoluijk.com/software/zeronoise/index.htm (http://www.guillermoluijk.com/software/zeronoise/index.htm)
By the way, most of the HDR software out there will do this as sort of a by-product. Normal Photoshop does this somewhat and here are another two popular HDR software packages:
http://www.hdrsoft.com/ (http://www.hdrsoft.com/)
http://www.mediachance.com/hdri/index.html (http://www.mediachance.com/hdri/index.html)
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I've been told about, but not tried, a technique in which one takes multiple frames of a scene. Manual settings, no movement in camera or tripod. Called image averaging.
In photoshop, layer the exposures. The bottom layer at 100 pct, next at lower opacity, and so on. 100/50/33/25%.
Hope this helps.
David
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Is there software that takes a stack of images and combines them for the purpose of noise reduction?
I'm thinking about situations where I don't have a tripod and the light levels are too low for handholding at a decent ISO. A single shot take at a high ISO would be noisy. If I took many shots, a computer could align the images and then compare them to assist with noise reduction. Is there software that already does this?
The essential point here, which some posters seem to have missed, is the situation you've referred to when you don't have a tripod and light levels are too low for handholding at a decent ISO.
The normal bracketing procedure for merging to HDR requires at least one long exposure for the shadows. In low light without a tripod, this technique will not produce a sharp result, and in any case its purpose is to extend DR.
The method of stacking using CS3 (or CS4) Extended (or some other stacking program) will quite significantly reduce the noise and increase the clarity and sharpness of an image at a high-ISO setting. My own experiments with a 5D resulted in a 1-2 stop advantage. For example, 5 or 6 images, taken at ISO 1600, after stacking can look like a single shot taken at ISO 400 with tripod, regarding over all noise and clarity. However, the 5D has a very slow fram rate of less than 3 frames per sec, which is not ideal for this type of procedure.
One day I'll get around to experimenting with my Nikon D700, and see how clean ISO 6400 can look after stacking say 9 images.
However, the Nikon has the facility to autobracket ISO in manual mode, which can both reduce noise and increase DR.
For example, one is using a lens without VR (such as the Nikkor 14-24), the light is poor, the subject is static but one doesn't have a tripod. One decides that 1/50th sec at F8 will ensure a sharp result, hand-held. Correct exposure at such shutter speed and aperture is achieved at, say, at ISO 400, retaining good highlight detail but resulting in noisy shadows because the 'subject brightness range' is high.
So one brackets ISO, producing a series of shots all at 1/50th shutter speed, from ISO 100 to ISO 6400, ISO 100 producing maximum highlight detail, and ISO 6400 producing maximum shadow detail, then one merges to HDR.
It would be interesting to compare both procedures.