Wavelets?

[northcanadian]

Hi all:

I'm just curious....do the wavelets enhance the signal and reduce noise?

Thanks

Roger

[Catanonia]

Not sure technically and someone will be along soon to give you the technical answer. But my laymans answer is that wavelets reduce the exposure of hot spots of the signal and eek out the contrasts underneath to reveal structure and local contrasts that over exposure has caused in an image.

Well that is how it seems to behave to me when I use it. TBH I am not a great fan of Wavelets in DSO. But for planetary, brilliant.

[JamesF]

Wavelets do not specifically reduce noise. In fact they can make noise more obvious. Stacking images eliminates some of the noise from an image to allow wavelet processing to work more successfully.

Very simplistically, the image you capture with your camera is subject to distortion which can be modelled mathematically with wavelets. By applying the reverse mathematical transformation to the captured image the idea is that you will recover something closer to what would have been present before the distortion occurred. It's a complex area and involves some very hairy maths. I certainly couldn't claim to have a good grasp of the mechanics of it myself.

James

[ollypenrice]

I'd also have said that wavelets increase noise, especially at small scales. The large scale sliders can be used fairly boldly but those at small scales pick up the noise as contrasts and increase it.

Olly

[JamesF]

I'd also have said that wavelets increase noise, especially at small scales. The large scale sliders can be used fairly boldly but those at small scales pick up the noise as contrasts and increase it.

I think what effectively happens is that noise is "sharpened" as well as the actual image, so just as desirable features in the image become more distinct, so does the noise.

James

[ollypenrice]

I think what effectively happens is that noise is "sharpened" as well as the actual image, so just as desirable features in the image become more distinct, so does the noise.

James

Indeed so. The small scale sliders can only be used on regions of bright signal with excellent S/N ratio.

Olly