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Full Spectrum and Infrared Photography

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31–34 of 34 posts

Re: Full Spectrum and Infrared Photography

#31
post #2

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 love…

By this measure, there is no "full spectrum" photography ever.

If you specify the source used for lighting, e.g. solar light, you can define precisely what "full spectrum" photography is, i.e. recording a bandwidth large enough so that any lighting energy that falls outside that range is negligible.

Re: Full Spectrum and Infrared Photography

#32
post #9

>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 ver…

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 usi…

Thanks!

The IR Chrome does not need a channel swap, just setting the white balance in-camera is enough to get a usable image.

The deep yellow looks mostly like a purple and yellow mess straight out of camera. Intent is for the yellow filter to block blue light, and a UV cut filter, leaving the blue channel to have ~almost solely IR, then subtracting that from the other channels to leave you with "clean" Red, Green, and IR as your three channels you can swap around. Probably the least dry camera signal approach of the bunch, unfortunately.

Re: Full Spectrum and Infrared Photography

#33
post #2

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 love…

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.

Re: Full Spectrum and Infrared Photography

#34
post #8

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...

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.

Yes, Seek RevealPro gives raw temperature data in radiometric tiff files. They are tiff files with temperatures in Celsius as float32 values in the second page of each .tiff. GUI image editors can have trouble dealing with these multi-page float tiffs but Python's PIL package can read it just fine.

Here's a basic script that converts them to greyscale uint8 with a fixed linear mapping, making them compatible with GUI panoramic stitching software.

https://github.com/dheera/iceland-thermal/blob/master/script...

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