[HN Gopher] Full Spectrum and Infrared Photography
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Full Spectrum and Infrared Photography
Author : alter_igel
Score : 42 points
Date : 2026-03-08 16:11 UTC (4 days ago)
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| fraywing wrote:
| This is really cool -- pedantically, I've always thought "full
| spectrum" is actually misleading from a traditional photographic
| sense. Like IR + visible light + UV != full spectrum. I'd love to
| see post-processed imagery of every-day life through an extended
| view of broader EM energy (similar to astrophotography)... like
| what does a city scene look like with x-rays and microwaves
| included?
|
| Side note: have always loved this image https://imgur.com/NZjWfWT
| of rainbows with UV and IR visible.
| IAmBroom wrote:
| You'd obviously have to use false-color, as most modern
| astronomy pictures do (even the ones that use visible tend to
| pump the saturation UP!).
|
| However, the amount of light from the sun drops off
| exponentially away from the peak at green-blue (yellow-green,
| after atmospheric filtering). You'd also have to really fake
| the dynamic range a lot to get it to look any different from
| IR+Vis+NUV. (If there was 0.001% as much x-ray light as there
| is, say, red light, DNA could only exist in the lightless
| depths of the ocean.)
|
| So, it would look like an IR+Vis photo (light falls off pretty
| fast in the UV, too), except the ones you've seen oversell the
| IR.
|
| So it would look like a Vis-light photo, with slightly shinier
| objects in it.
|
| Sorry.
| mncharity wrote:
| I like distinguishing "light" (physical world) from "color"
| (species-specific biology). Sunbeam blue _light_ is already
| less intense than NIR-I, but human bio juices the blue. Most
| humans are bright-light trichromats and low-light
| monochromats. Rod sensitivity is 3 orders of magnitude up,
| with single-ish photon sensitivity. Some amphibians have an
| extra rod type, for low-light bichromaticity. Some deep-sea
| fish are bright mono and dark _lots_ chromats (12+ rod
| opsins). So why not imagine seeing the world with a triple
| (or more) of short-wavelength super-rods, a few orders of
| magnitude more sensitive still, with whatever curves seem
| fun? Perhaps curves naturally selected for by "makes
| intriguing images of the world for social media"...
| _Microft wrote:
| By this measure, there is no "full spectrum" photography ever.
| avidiax wrote:
| One thing I've wondered about is IR fluorescence photography.
|
| I've seen some examples in document forensics where a page that
| looks blank (or at least the ink is unrecognizably smudged)
| because of water exposure is completely legible with an infrared
| photo illuminated by UV.
|
| I suspect there must be a hidden world only visible in IR and UV
| (and long-wave IR, e.g. "thermal").
| NoiseBert69 wrote:
| You're considering whether it would be possible - and perhaps
| quite elegant - to use an XY-scanner to raster-scan the end of an
| optical fiber across a prism, disperse the light, and then
| capture the resulting spectrum with a CCD line sensor.
|
| With that setup, each pixel on the line sensor would effectively
| record the full spectral content of the light at that scanned
| position, all in a single acquisition.
| asdff wrote:
| A problem for multispectral imagery (even within visible rgb),
| is that the wavelengths of light are different so the lens
| cannot be in focus for all spectrum at once. I have tested this
| out with a few of my slr lenses. If you have blue channel
| perfectly in focus, red isn't just a little out of focus, it is
| actually noticeably way out.
| tomtom1337 wrote:
| This is called chromatic aberration, for those who are
| intrigued.
|
| Given that regular phone cameras have sensors that detect
| RGB, I wonder if one could notice improved image sharpness if
| one had three camera lenses (and used single-color sensors)
| next to one another laterally, with a color filter for R, G
| and B for each one respectively. So that the camera could
| focus perfectly for each wavelength.
| asdff wrote:
| Next issue would be the perspective distortion in the
| merged image
| lytfyre wrote:
| there are lenses out there designed for apochromatic
| performance across the UV-Vis-IR band, but they tend to be
| really pricey.
|
| The Coastal Optical 60mm is a frequently cited one. UV in
| particular is challenging, because glass that works well in
| the visible light range can be quite poorly translucent in
| UV. Quartz is better, but drives up the cost a lot, and comes
| with other tradeoffs.
| dheera wrote:
| I've had this problem as well, but it's just due to optical
| properties of the lens and extremely consistent from image to
| image, so you can calibrate and correct for it as long as you
| focus each wavelength and collect data separately.
| asdff wrote:
| I don't think you can property calibrate for it unless you
| also move the camera to compensate for focus breathing. I'm
| not sure if that would fully account for it either. That
| being said these things are only very noticeable pixel
| peeping.
| dheera wrote:
| Focus breathing can be compensated for. The "breathing"
| only changes the effective focal length, not the location
| of the camera, so you can map the pixels to match where
| they should be and bilinear/bicubic interpolate
| appropriately.
|
| Shoot a checkerboard at both wavelengths each focused
| properly and then compute the mapping.
|
| If you're shooting macro stuff then _maybe_ you are
| changing the effective location of the camera slightly
| depending on the exact mechanics of the lens and whether
| the aperture slides with the focusing, but the couple of
| mm shift in camera location won 't matter for landscapes.
|
| Alternatively, use cine lenses which are engineered not
| to breathe, but they are typically more expensive for
| that reason.
| tomtom1337 wrote:
| You could probably use just an X-scanner, and instead of a CCD
| line sensor, use a regular 2D image sensor if you used a "1
| pixel wide" slit aperture to crop the image perpendicularly to
| the direction that the prism disperses the light. So instead of
| a single pixel being dispersed, you disperse a line.
|
| You would reduce the time required by the root of the number of
| pixels you want (assuming a square image).
|
| (This is what we do in momentum-resolved electron energy loss
| spectroscopy. In that situation we have electromagnetic lenses
| that focus the electrons that have been dispersed, so we don't
| have as bad a chromatic aberration problem as the other
| response mentions).
|
| I would love to see e.g. a butterfly image with a slider that I
| could drag to choose the wavelength shown!!
| NoiseBert69 wrote:
| Very nice idea! That makes it much easier!
| mncharity wrote:
| > I would love to see e.g. a butterfly image with a slider
| that I could drag to choose the wavelength shown!!
|
| Here[1] are some 31-band hyperspectral images of butterflies.
| Numpy/pillow can unpack the .mat files into normal images.
| Then perhaps vibecode a slider, or just browse the band
| images?
|
| [1] http://www.ok.sc.e.titech.ac.jp/res/MSI/MSIdata31.html
| (includes 8 butterfly 31-band hyperspectral visible-light
| images). These butterflies are also their VIS-SNIR dataset,
| and others.
|
| I knew of the site having explored "First-tier physical-
| sciences graduate students are often deeply confused about
| color. Color is commonly taught, starting in K... very very
| poorly. So can we create K-3 interactive content centered
| around spectra, and give an actionable understanding of
| color?"
| dheera wrote:
| Related project: I shot a lot of landscapes in Iceland using a
| thermal (long wave IR) camera to show geologic phenomena in
| action. This involved stitching together a lot of (narrow FOV)
| thermal images and overlaying it on top of visible camera images
| for context.
|
| https://petapixel.com/2019/07/13/shooting-high-res-thermal-p...
| vjvjvjvjghv wrote:
| Very cool!
| lytfyre wrote:
| >Whenever shooting a subject with a mixture of visible and
| infrared light, it becomes readily apparent that infrared light
| focuses differently from visible light. For many subjects, this
| can mean having to choose between crisp visible contours and an
| odd pink glow, or blurred edges with some unusual pink features
| inside. Some things never look sharp no matter where you move the
| focus.
|
| The extent of this effect is very lens dependent. It also occurs
| in different colours of visible light too, depending on how well
| the lens design accounts for it. Optically, the term is
| "Chromatic Aberration" - lens designers try and account for it in
| the visible spectrum with optical design and lens coatings, and
| modern designs are generally extremely well corrected in the
| visible spectrum. _Usually_ designers aren't worried about the
| design correctly handing convergence into IR and UV, so how well
| designs focus them to the same point as the visible spectrum is
| hit or miss. There's specialist lenses out there that are
| designed specifically for wide spectrum apochromatism, but they
| tend to be special purpose and very expensive - especially if
| they handle UV.
|
| The author mentions it at the bottom of the post as something
| they're interested in trying out, but I've found it very fun to
| play with dual bandpass filters - they pass a part of the Visible
| Spectrum + IR, which creates some interesting options in editing
| for visual display. There's an example in this set I shot with
| different filters -
| https://www.reddit.com/r/infraredphotography/comments/1dnki0...
| miladyincontrol wrote:
| Superachromat is the term you're looking for in terms of lenses
| corrected throughout IR to UV. They're not actually that
| expensive if you know where to look, I got my Zeiss 250mm
| supeachromat for about $500 from a Japanese seller. Works a
| treat for full spectrum film work especially on a system that
| lets you swap between film backs, if not for the woeful cost of
| film these days.
| shagie wrote:
| > it becomes readily apparent that infrared light focuses
| differently from visible light.
|
| On old school manual focus capable lenses you'll note a small
| (often red when colors were used to indicate f stops) dot to
| the left of the focus indication line.
|
| https://commons.wikimedia.org/wiki/File:AiS_Nikkor_85mm-2.0_...
|
| On more modern lenses, is simply a dot.
| https://www.mir.com.my/rb/photography/companies/nikon/nikkor...
|
| This was the offset for IR photography. You'd focus normally,
| and then make note of the focus distance and then line up the
| focus distance with the red dot for IR offset.
|
| ---
|
| The UV photography often was done with other glass since the
| glass used by most lenses does an ok job of filtering UV light.
|
| The 105mm UV lens for example -
| https://www.mir.com.my/rb/photography//hardwares/speciallens...
|
| It's an oddball enough lens that others don't often make that
| it keeps getting special runs.
|
| https://www.nikon.com/business/industrial-lenses/lineup/uv/
|
| Costal Optics did a run of of the lens too -
| https://diglloyd.com/prem/s/DAP/Coastal60f4/Coastal60f4.html...
|
| ---
|
| One of the photographers I've stumbled across from days of old
| who did UV nature photography (what do bees see?)
| http://www.naturfotograf.com/uvstart.html
| regus wrote:
| Looks like grainydays on youtube can finally stop chugging
| flaming hot mountain dew everyday in the hopes that Kodak will
| bring back Aerochrome.
|
| https://www.youtube.com/watch?v=v5KBQd_DkQw
| JKCalhoun wrote:
| I like the idea of using the IR, where it shows a greater degree
| of contrast, to act as a "contrast mask" on the visible light
| image.
|
| I'm thinking of the beautiful cloud detail in the one IR shot
| where the visible light photo had lost all of that. Seems like
| some compositing (sort of like HDR) you could try to pull in the
| best of both worlds.
| mcdeltat wrote:
| For contrast specifically, you can get much of that effect with
| a red filter. Just removing the majority blue/green components
| already changes the lighting massively. Can add a polarising
| filter too for an even more extreme effect on the sky.
|
| E.g. this photo (looks quite HDR'd but it's not, it's barely
| edited): https://rjones.photos/gallery/photo/20251207-img9638
| mcdeltat wrote:
| This is super cool, I want one now
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