Visible Spectrum: Can it be color shifted?

By | April 22, 2013

Is there any device to shift the spectrum of what is seen so red becomes orange, orange becomes yellow, yellow becomes green and so on, smoothly?

A typical human eye will respond to wavelengths from about 390 to 700 nm.[1] In terms of frequency, this corresponds to a band in the vicinity of 430–790 THz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum (see: luminosity function). The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths.

sRGB rendering of the spectrum of visible light
Color Frequency Wavelength
violet 668–789 THz 380–450 nm
blue 606–668 THz 450–495 nm
green 526–606 THz 495–570 nm
yellow 508–526 THz 570–590 nm
orange 484–508 THz 590–620 nm
red 400–484 THz 620–750 nm

via Visible spectrum – Wikipedia, the free encyclopedia.

I haven’t found any device that will do this but I did find this interesting paper:

Gravitational Blueshift and Redshift generated at Laboratory Scale

… it is possible to produce gravitational blueshift and redshift at laboratory scale by means of a device that can strongly intensify the local gravitational potential… Thus, by using this device, it is
possible to generate electromagnetic radiation of any frequency, from ELF radiation (f < 10Hz) up to high energy gamma-rays. In this case, several uses, such as in medical imaging, radiotherapy and radioisotope production for PET (positron emission tomography) scanning and others, could be devised. The device is smaller and less costly than conventional sources of gamma rays.

via Inria

A lens can filter out colors, but I’m asking a different question, how to change one color into another. X-ray film seems to red-shift x-rays into the visible spectrum. How does it do that? Answer: It doesn’t. There is no shift, but x-rays hitting some substances can cause light to be emitted.

… the conversion of a relatively small number of X-ray photons of high energy to a large number of light photons of low energy is due predominantly to X-ray absorption via the photoelectric effect in the high Z components of the phosphor. … – link

Quick refresher on the photoelectric effect:

In the photoelectric effect, electrons are emitted from solids, liquids or gases when they absorb energy from light. Electrons emitted in this manner may be called photoelectrons.[1][2]

Heinrich Hertz in 1887 [2][3] discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905 Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets. Einstein was awarded the Nobel Prize in 1921 for “his discovery of the law of the photoelectric effect”.[4]

The photoelectric effect requires photons with energies from a few electronvolts to over 1 MeV in high atomic number elements. – link

Just use photo editing software? Here is an original image I took hiking at table mountain this weekend:

20130421-211841.jpg

In this next photo, I used the free Paint.net program to shift the hue by a value of 100 positive. As you can see, yellow is green, green is blue, and blue is now purple. This is a blueshift, shortening the color wavelengths, moving reds toward the blue. That’s not obvious because the blue sky now looks more red, but the blue is actually now violet and the yellow is green. If my camera picked up infrared outside of human vision, assuming the photo format kept and could manipulate that data, this shift would show it. Similarly, if my camera picked up x-rays, a redshift would move it into the visible spectrum.

20130421-shift1

Here is the original image redshifted. The blue sky becomes green with a redshift, the yellow flowers become red:

20130421-shift2

Next, here is a more dramatic blueshift, moving the yellow flowers all the way to blue:

20130421-shift3

What I was really curious about is if my iPhone camera includes any information outside of the visible spectrum. Unfortunately, Paint.net’s hue feature just cycles the visible colors. You can’t move things into the red and just keep going more and more red until you move into infrared. This makes complete sense as computers are designed only to work with the visible spectrum.

Still, I wonder if what I’m envisioning could be done with software: Shift colors up to the point where only certain colors would be visible after a big enough shift in one direction. In other words, when the colors move out of the visible range, I just want them to become invisible, not to cycle around. The color spectrum is not a circle.

In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum (the filter thus looks black or deep red). (“Infrared filter” may refer either to this type of filter or to one that blocks infrared but passes other wavelengths.)

When these filters are used together with infrared-sensitive film or sensors, very interesting “in-camera effects” can be obtained; false-color or black-and-white images with a dreamlike or sometimes lurid appearance known as the “Wood Effect,” an effect mainly caused by foliage (such as tree leaves and grass) strongly reflecting in the same way visible light is reflected from snow.[1] There is a small contribution from chlorophyll fluorescence, but this is marginal and is not the real cause of the brightness seen in infrared photographs. The effect is named after the infrared photography pioneer Robert W. Wood, and not after the material wood, which does not strongly reflect infrared.

The other attributes of infrared photographs include very dark skies and penetration of atmospheric haze, caused by reduced Rayleigh scattering and Mie scattering, respectively, compared to visible light. The dark skies, in turn, result in less infrared light in shadows and dark reflections of those skies from water, and clouds will stand out strongly. These wavelengths also penetrate a few millimeters into skin and give a milky look to portraits, although eyes often look black. – wikipedia

File:Tree example IR.jpg

Can the iPhone 4S take photos like these? It seems not and I think there is even a filter to block infrared that the iPhone 4 did not have according to this: http://www.cameratechnica.com/2011/10/31/how-good-is-the-iphone-4s-cameras-ir-filter/

Here is a claimed iPhone infrared photography:

I have a whole set of genuine infrared photos here, all taken with just an iPhone and a Hoya R72 infrared filter held over the lens: http://www.flickr.com/photos/matt_brock/sets/72157624198109814/

Have fun.

0 thoughts on “Visible Spectrum: Can it be color shifted?

  1. Kurt

    The first paper you linked to says they’re using gravity shielding? When did gravitational shielding become real and usable so easily?

    Reply
    1. Xeno Post author

      According to patent Pi0805046-5

      “… any substance subjected to the action of an oscillating electromagnetic field has its gravitational mass reduced and the gravity acceleration in any transversal direction to the substance is reduced at the same proportion of the gravitational mass reduction. According to this principle, here called General Principle of Gravity Control, the change in the gravitational mass of the substance and in the gravity acceleration in any transversal direction to the substance is directly proportional to the product of the electromagnetic energy density applied to the substance for the refraction index, and inversely proportional to the mass density of the substance (q.v. ‚ÄúMathematical Foundations of the Relativistic Theory of Quantum Gravity‚Äù).”

      Sounds like science fiction to me. Being in an oscillating em field does not reduce gravitational mass, as far as I know. Then again…

      Reply

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