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.
Author here. I agree with you, "full spectrum" is a generous marketing phrase for what might more accurately be called _extended_ spectrum.
People way smarter than me have been able to achieve DIY spatial imaging with x-rays via compressed sensing [1] and with microwaves via phased arrays [2].
Optical wavelengths seem to be at a sweet spot of good angular resolution, varied natural sources, and harmless to humans.
Playing with a hyper-spectral imager makes you rethink how we see things. I've talked about this before, but human vision essentially "low resolution" on the spectral bands. Using an HSI that "sees" in 4nm spectral slices from 350-1000nm is really interesting (Cubert Ultris X20 Plus). There's so much spectral information that we just totally miss. I really wish the equipment for capturing images at these higher spectral resolutions wasn't so expensive so we could see people experimenting with them on a large scale. The one I got to work with was more than a nice SUV and that's cheap in the space. The ones we looked at from Headwall that did something like 400-2500nm started at $250k. Those weren't even full-frame imagers like the Ultris, they were line scanning imagers. That massive cost jump was down to the fact that from ~1050nm+ you need much different hardware to capture spectral data.
If anyone is interested in some technical aspects of the "full frame" HSI I worked with, it's quite interesting. It had a 20MP Monochromatic Sensor that captured single-band 12-bit data behind an array of lenses that split the incoming spectral range (350-100nm) into 164 individual 4nm wide bands of light that hit 410x410px squares on the sensor. The sensor can capture from 350-1100, but the QE drops of really fast past about 850nm and the product limited the upper range to 1000nm. I'm sure I munged something there, but you should get the general idea. I highly recommend researching the space of HSI, it's fascinating.
Last thing to point out, when working with an HSI like this, one thing you can do is capture a "spectral fingerprint". Since you've gone from three bands on spectral intensity information to, in our case, 164 bands you have the ability to turn that high-density spectral data for each pixel into essentially a line graph. Using that information you can do matching against a database of known spectral fingerprints and identify materials and material properties really well. In the multi-spectra world you'll see this capability used to identify crop health. In the hyperspectral world you can identify so much more. For instance, it can see skin anomalies that aren't visible to the human eye. You can identify specific minerals in a picture of a bunch of rocks (you need up into the 2500nm range for this though). You can easily spot foreign objects on a conveyor of food items. Overall, it's a long list of capabilities and I'm certain there are many more uses we could discover if the imagers were cheaper. And if you are into the wider ML world (not just focused on LLMs I mean), you'll see ML Classification Models being trained on these spectral fingerprints as well.
Anyway, the "full-spectrum" is fascinating, especially when you are able to slice it thin.
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").
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.
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.
Author here. Amazing work! The visible and thermal compositing is done really well and gives back so much detail and context that is lost in purely thermal images.
Does your IR camera give you access to raw temperature data? I've briefly played with a cheap thermal camera and it seemed to assign its own colours varyingly depending on the dynamic range of temperatures in view.
>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...
Author here. Great point about the lens-dependent abberation, I mentioned this briefly in my earlier write-up about doing the full spectrum mod [1] but forgot to mention it by name here. I've been trying to get by without spending a lot of money on lenses and have gotten a lot of mileage out of a cheap used 50mm lens that _feels_ like it's just one or two solid glass elements. Fortunately the old camera mount I'm using means all the lenses for it are used, old, and super cheap secondhand. I'm about to try my luck with a 300mm lens. IR should be fun but we'll see if I can squeeze any UV at all through that.
Beautiful shots you have with your own full spectrum camera. Originally I somewhat dismissed the Kolari IR Chrome filter because the suggested combination with a channel swap and custom LUT felt a little too heavily edited for me and I prefer to stay close to the dry camera signal. The shot with the Tiffen Deep Yellow filter is gorgeous, how does that one look on the camera LCD without the channel swap?
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.
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[ 3.0 ms ] story [ 26.3 ms ] threadSide note: have always loved this image https://imgur.com/NZjWfWT of rainbows with UV and IR visible.
People way smarter than me have been able to achieve DIY spatial imaging with x-rays via compressed sensing [1] and with microwaves via phased arrays [2].
Optical wavelengths seem to be at a sweet spot of good angular resolution, varied natural sources, and harmless to humans.
[1] https://www.youtube.com/watch?v=EuVgGrun1V0
[2] https://www.youtube.com/watch?v=sXwDrcd1t-E
If anyone is interested in some technical aspects of the "full frame" HSI I worked with, it's quite interesting. It had a 20MP Monochromatic Sensor that captured single-band 12-bit data behind an array of lenses that split the incoming spectral range (350-100nm) into 164 individual 4nm wide bands of light that hit 410x410px squares on the sensor. The sensor can capture from 350-1100, but the QE drops of really fast past about 850nm and the product limited the upper range to 1000nm. I'm sure I munged something there, but you should get the general idea. I highly recommend researching the space of HSI, it's fascinating.
Last thing to point out, when working with an HSI like this, one thing you can do is capture a "spectral fingerprint". Since you've gone from three bands on spectral intensity information to, in our case, 164 bands you have the ability to turn that high-density spectral data for each pixel into essentially a line graph. Using that information you can do matching against a database of known spectral fingerprints and identify materials and material properties really well. In the multi-spectra world you'll see this capability used to identify crop health. In the hyperspectral world you can identify so much more. For instance, it can see skin anomalies that aren't visible to the human eye. You can identify specific minerals in a picture of a bunch of rocks (you need up into the 2500nm range for this though). You can easily spot foreign objects on a conveyor of food items. Overall, it's a long list of capabilities and I'm certain there are many more uses we could discover if the imagers were cheaper. And if you are into the wider ML world (not just focused on LLMs I mean), you'll see ML Classification Models being trained on these spectral fingerprints as well.
Anyway, the "full-spectrum" is fascinating, especially when you are able to slice it thin.
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").
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.
https://petapixel.com/2019/07/13/shooting-high-res-thermal-p...
Does your IR camera give you access to raw temperature data? I've briefly played with a cheap thermal camera and it seemed to assign its own colours varyingly depending on the dynamic range of temperatures in view.
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...
Beautiful shots you have with your own full spectrum camera. Originally I somewhat dismissed the Kolari IR Chrome filter because the suggested combination with a channel swap and custom LUT felt a little too heavily edited for me and I prefer to stay close to the dry camera signal. The shot with the Tiffen Deep Yellow filter is gorgeous, how does that one look on the camera LCD without the channel swap?
[1] https://timstr.website/blog/diyfullspectrummod.html
https://www.youtube.com/watch?v=v5KBQd_DkQw
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.