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Step 2Geeky Notes
The "Overlay" blending mode works by using values above 50% grey to brighten an image and values below 50% grey to darken an image.
This is basically analogous to waveform addition, considering 50% grey the zero level.
Note that if you make a high and low pass image and combine it with itself (like in the Terminator head image) you should get the original image, but you don't!
Why is that, you ask?
Well, a Gaussian Blur isn't a true low pass. It merely smears around the high frequency data all through the image. The High Pass filter is similar in its defects. This filter blurs the image, inverts it, and averages it with the original image (Photoshop 6: Guassian Blur, Invert, Normal Blend mode at 50% opacity).
Nevertheless, you get something that's quite close to the original image.
If you can transform the image into Fourier space to actually strip off the various frequency bands and recombine them, you should get exactly the original image.
A note on sound:
The terms "color", "life", and "clarity" are used to describe the low and high frequencies of sound and light. In a song, the low frequencies are harder to discern than the high frequencies, but are the foundation of a song and provide life and color to a song. The high frequencies are more easily discernable spatially than low frequencies. In other words, the source of a deep thud (a low frequency sound) is much harder to locate than a high-pitched (high frequency) bird song. Similarly, a low frequency image is much harder to recognize than a high frequency image. Lastly, a song without low frequencies is flat and dull, just as an image without low frequencies is flat and lifeless.
This is basically analogous to waveform addition, considering 50% grey the zero level.
Note that if you make a high and low pass image and combine it with itself (like in the Terminator head image) you should get the original image, but you don't!
Why is that, you ask?
Well, a Gaussian Blur isn't a true low pass. It merely smears around the high frequency data all through the image. The High Pass filter is similar in its defects. This filter blurs the image, inverts it, and averages it with the original image (Photoshop 6: Guassian Blur, Invert, Normal Blend mode at 50% opacity).
Nevertheless, you get something that's quite close to the original image.
If you can transform the image into Fourier space to actually strip off the various frequency bands and recombine them, you should get exactly the original image.
A note on sound:
The terms "color", "life", and "clarity" are used to describe the low and high frequencies of sound and light. In a song, the low frequencies are harder to discern than the high frequencies, but are the foundation of a song and provide life and color to a song. The high frequencies are more easily discernable spatially than low frequencies. In other words, the source of a deep thud (a low frequency sound) is much harder to locate than a high-pitched (high frequency) bird song. Similarly, a low frequency image is much harder to recognize than a high frequency image. Lastly, a song without low frequencies is flat and dull, just as an image without low frequencies is flat and lifeless.
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