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I am familiar with and have shot in Infrared, give or take above the 700nm range with my Nikon D750 and an IR filter over the lens. Does anybody know of other wavelength-specific types of photography? For example, say I wanted to shoot in the 400nm to 500nm range, would this be practical? Has anyone done anything like this before? Are filters like this available to be purchased anywhere, without costing an arm and a leg?

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    What one photographer considers costing an arm and a leg is what another photographer may consider a haircut. – Michael C Jul 12 '18 at 5:07
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    X-Ray machines? – wally Jul 12 '18 at 12:41
  • I think we need a definition of photography. Near IR and Thermal IR are generally considered separate wavelengths but I don't know of anyone doing "pictorial" work with an InGaAs sensor. LWIR TIR is getting pretty cheap too these days... I think you can get a 4MP sensor for $50k including the cryogenics. I do know of a few FA guys who have used x-rays but can't think of anyone using microwave tomography for pretty stuff. It also seems that you are implying that you are interested solely in wavelengths which are detectable by your DSLR. Is this true? – PhotoScientist Jul 13 '18 at 2:53
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The visual range of the electromagnetic spectrum covers slightly less than one octave (wavelength 400 thru 700 nanometers; the center of this range is 1/50,000 of an inch). Mankind evolved to perceive visual images within this range likely because earth’s atmosphere is transparent in this range. However the electrometric spectrum extends from Gamma Rays (1 Angstrom unit) to Radio waves (several mile).

We can generate graphics that cover the entire range of the electromagnetic spectrum. Since we can’t see most of this range, we change the name from photography to imaging.

Some examples of images made outside the 1 octave of the visual range. Radar, we generate an image using radio waves. Ultrasound, images made using sound waves. X-ray, images made using the wavelengths centered on 1 millimicron. Ultraviolet, just one octave shorter than the visual range. Infrared, one octave longer in wave length than the visual range.

When we image outside the visual range the images we see are unreal; we can’t see by these wavelengths, but we can conceive what things look like. Nowadays we image using the electron microscope and radio telescope. In other words, we can visualize the ultra-tiny and the super large.

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    Might be worth pointing out that the ultrasound example is a bit of an odd man out, since sound waves are not part of the electro-magnetic spectrum. It's still a valid example of imaging, but it's completely different... – twalberg Jul 12 '18 at 15:31
  • @ twalberg -- Different however we image by temperature differences and I have seen attempts to image by smell. Also experiments using electric stimulation of the taste buds can send visual images that blind people interpret as sight, strange but true. – Alan Marcus Jul 12 '18 at 15:54
  • The principles that apply to working with light waves also apply to sound waves. Also, People who "see" with sound, process "images" with the same part of the brain that "normal" people use to see light. – xiota Jul 12 '18 at 17:46
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Extended/Full-Spectrum Photography

Here is a graph to show the general sensitivity of a sensor to various wavelengths:

CCD Sensor Spectrum Response

By putting an IR filter over your lens, you were able to take pictures in the near-infrared range because the hot mirror is not perfect. You can do a "full-spectrum conversion" by replacing the hot mirror in your camera with plain glass. Then, in principle, any frequency from UV to near-IR can be photographed (Around 300nm to 1000nm, shown in the graph). You can use filters to isolate the frequencies you're interested in.

Use of Non-Visible Spectra

Although astrophotography and forensic applications most readily come to mind, there are other uses for extended-spectrum photography. For instance Blue+IR may be used to analyze vegetation.

There are sensors that are used to detect x-rays used in medicine, archaeology, and airports. X-ray crystalography performed by Rosalind Franklin (on film!?) was instrumental in determining the structure of DNA.

MRI machines "photograph" using magnetic resonance instead of light. Ultrasound machines do the same with sound waves to create "photographs" of the heart (echocardiograms) or a fetus. Blind people who use sound to "see" use the same region of the brain that "normal" people use to see with their eyes.

(Color) Filters

If you refer back to the graph, you will see that 400-500nm corresponds roughly to blue-green. B&W photographers often use color filters: Blue, Green, Yellow, Orange, and Red. But with digital cameras, there's not much need to buy colored filters anymore because they're pretty much built into the Bayer color array located over the sensor of your camera.

Although individual filters may not be too expensive (costs range from a few to a few hundred dollars, depending on the type of filter), it can add up if you choose to purchase too many. Unless you convert your camera to full spectrum, there usually isn't much need to buy many color filters. (Exceptions include IR, UV, didymium, ND, polarizing filters.)

Notes

  • Obviously, your digital camera cannot record frequencies outside the range that the sensor is sensitive to (approximately 300-1000nm).
  • Although some may not consider imaging of the electromagnetic spectrum outside of the visible range to be "photography", they do still involve photons.

  • For non-electromagnetic energies, "photograph" is used as a metaphor. Hasn't anyone ever heard a kid being told about their "first photograph", the ultrasound from when they were still inside the womb?

  • Reasons you might still want to use color filters, per @MichaelClark:

    When using a Bayer masked camera to do B&W work, use of an additional color filter in front of the lens allows one to increase the overall exposure without blowing out one color channel (that one would plan to reduce in raw processing anyway). This allows a higher signal-to-noise ratio using the wavelengths one plans to emphasize.

    Are there reasons to use color filters with digital cameras?
    Do I still need to use color filters for images that are to be presented in monochrome (B&W)?

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    When using a Bayer masked camera to do B&W work, use of an additional color filter in front of the lens allows one to increase the overall exposure without blowing out one color channel (that one would plan to reduce in raw processing anyway). This allows a higher signal-to-noise ratio using the wavelengths one plans to emphasize. Do I still need to use color filters for images that are to be presented in monochrome (B&W)? and Are there reasons to use colour filters with digital cameras? – Michael C Jul 12 '18 at 16:46
  • Do you have a concrete example of when you would want to use a color filter to prevent another color channel from being blown out? – xiota Jul 12 '18 at 18:34
  • In some digital cameras the sensitivity of the R channel of the Bayer matrix goes up to some extent at wavelengths shorter than 400 nm, and many cameras the sensitivity of the blue channel goes down at longer wavelengths than shown in the figure above. So although the figure above does a very good job at describing the principles, the R G B curves are likely not to exactly describe other cameras. This affects the false colours that a camera converted to full spectrum can yield with a certain filter on the objective. – Pedro Aphalo Jul 12 '18 at 22:57
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One type of camera not yet mentioned are multispectral and hyperspectral cameras. In simplest terms, these cameras are usually sensitive to a range of wavelengths somewhere between UVA and near infra-red, so in this respect rather similar to normal digital cameras, but unlike normal photographic cameras that have the ability to distinguish the three colours red, green and blue (which match human colour vision), these cameras can have up to a few hundred "colour" channels per image pixel. Such cameras are getting into more widespread use with the wider availability of drones. They can be used for widely different things going from remotely identifying plant species growing in fields, to locating the areas with richer mineral in open pit mines.

There are many reasons for interest in UV photography: many birds and insects have visual systems that are sensitive to UV, and consequently flowers and feathers can have patterns invisible to humans but vital for the survival or behaviour of these species; artists may be interested in the unusual look of everyday objects; etc.

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Radio telescopes?

X-ray machines?

Ultraviolet photography?

Ok, we need to address some issues here. Different wavelength needs different apparatus design because of physics.

Radio is an electromagnetic wave, the same as visible light... but it turns that it can pass thru you, the wall and your camera. So you can not take a suitable photo of you or the wall using your camera. You need a big antenna because the wavelength is pretty big.

Another problem is that some wavelengths cannot easily bend to focus. For example, a normal x-ray machine does not focus the light to the plane. What it does is that spreads the rays from a tiny spot, therefore producing sharp shadows, sharp enough for that purpose.

There are some "lenses" to focus this beams stacking a lot of them. So this is, in fact, one type of photography.

https://en.wikipedia.org/wiki/Backscatter_X-ray

http://photon-science.desy.de/research/research_teams/fs_petra/overview/x_ray_optics/refractive_x_ray_lenses/index_eng.html

It is most likely illegal to go around flashing a person with Xrays to take a portrait.

So there is a physical limit where it is suitable to take pictures. And normally that range is near the visible light. That, in fact, is why living organisms perceive those wavelengths in the first place. Some cannot be perceived because they pass thru you, some cannot be perceived because they kill you.

The one photo that is somehow suitable is Ultraviolet one. Take a look at the Wikipedia article for example https://en.wikipedia.org/wiki/Ultraviolet_photography


Another different aspect is non-photographic images, reflecting or "refracting" and blocking some other stuff that is not light... you know? the Photo part of photo-graphy?

You can reflect sound waves, magnetic waves, gravitational waves, electrons... you can make an image pushing pins https://www.google.com.mx/search?q=pin+impression+toy but that is not "photography" probably imagery...

  • So those X-ray glasses I saw advertised in comic books are real? – Michael C Jul 12 '18 at 16:50
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For completeness only - vast quantities of arms and legs required.

An MRI (Magnetic Resonance Imaging) device meets the requirement for images using electromagnetic 'rays' at other than IR or visible frequencies.
The functionality of an MRI scanner may be visualised several ways.
One visualisation is that a high intensity magnetic field is applied to the "sample" (= eg me on a number of recent occasions) causing the protons in the sample to precess on their axes, with the emission of electromagnetic signals which can be detected. Various "shaped pulses" are applied to cause precession and decay of precession to follow certain paths.
Applied arcane technical magic allows the identification of the precession rate at specific 3D locations, allowing a 3D image of the sample to be reconstructed.

2D slice of 3D image of parts of me - far less exciting than it may seem :-).

enter image description here

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