Sometimes it’s just not possible to capture an “ideal” image, often because the subject itself reflects light unevenly. Normalization offers a way to deal with these kinds of images. To see what normalization can do, take a look at the before and after images that Thor Vollset has posted on his Scorpion blog: “AreaFilter adds Image Normalization to Scorpion 8.1”.
Unfortunately, even though Thor’s images speak volumes, they don’t actually explain what normalization is doing. I was going to take a stab at this myself, but then I thought, since Wikipedia has done such a great job, why bother? Instead, here’s a link to the Wikipedia entry for normalization.
And finally, to put it all together with before and after images AND histograms showing the distribution of intensities, take a look at the “Normalize Intensities” tutorial on the Roborealm website.
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2 comments:
Note that Scorpion is using convolution or something like that to get even intensity across image. That's something which isn't normally covered by normalization algorithms.
What is normalization? - this is a good question. We use a non-linear algorithm to remove the low frequency intensity variations in the images before fixing the light intensity level :)
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