#which scatters shorter wavelengths of light (such as blue and green) and allows longer wavelengths (such as red and orange) to dominate the

[justin-travel-2024]

"Crimson Horizons: Behold the Enchanting Red Sunset in Sweden's Breathtaking Landscapes"

"Captivating Beauty: Witness the Majestic Red Sunset in Sweden and Immerse Yourself in Nature's Radiant Splendor"

[wisdomrays]

TAFAKKUR: Part 71

Blue Light, Daytime Sleep and the Prophetic Tradition

Sleep is a blessing from God. Humans spend around one third of their lives sleeping. Sleep is essential for the performance of important daily acts such as speech, memory, and original or flexible thinking. At the end of a busy day our body looks forward to relaxing and restoring its energy for the next day. Although sleep plays a significant role in our daily life, most of us rarely find and use suitable periods for a good sleep. There is no fixed amount of time that everyone needs to sleep, since this varies from person to person depending on several different factors, such as genetic background, age, and daily activities. For an adult individual the average time spent sleeping can vary from six to eight hours.1 We need to make some time for rest and recovery.

In reality, people who habitually go to sleep very late at night have difficulty waking up in the morning. This happens because of disturbances in the body’s internal clock or circadian rhythms. Circadian rhythms are important in determining the sleeping and feeding patterns of all creatures.

There are clear patterns of brainwave activity, hormone production, adjustments to body temperature, blood pressure and many other biological activities linked to this daily cycle.

It is known that melatonin, a hormone with a high level of concentration at night and low levels during daytime, regulates the circadian rhythm. However, there are other factors that activate or inhibit the internal body clock and several studies have demonstrated that light on the eye’s retina is a more powerful influence on human circadian rhythms.

Blue light

As light that is radiated from the sun travels through the atmosphere, some shorter wavelengths of light, such as violet and blue, are absorbed by gas molecules and then scattered all around the sky. This gives the sky a blue appearance. According to Dr. Mark Rea, director of the Lighting Research Center, our daily rhythms are in fact blue sky detectors, and he notes, “Blue sky is ideal for stimulating the circadian system because it’s the right color and intensity, and it’s ‘on’ at the correct time for the right duration, the entire day.”

Researchers have used light for jet-setters, sleep-troubled patients, and shift workers to set their body clocks and solve sleep problems. Moreover, they claim the dogma that the 24-hour biological clock is set by light alone is a misconception that many scientists have believed for years. Steven Lockley of Brigham and Women's Hospital, a Harvard research and teaching affiliate says, “The visual system in humans is most sensitive to green light, but when we exposed twelve healthy young men and women to the same amount of either green or blue light, their 24-hour rhythms shifted twice as much with blue than with green.” After exposure to blue light, their body clocks were rearranged by three hours, whereas the effect of green light was a change of about 1.5 hours. So, if your eyelids get heavy around 11 p.m., 6.5 hours of exposure to blue light will keep you up until 2 a.m. Since television and computer screens produce blue light, watching them too much at night may inappropriately affect the sleep cycle. However, if a change in shift makes you sleepless at 4 a.m., proper blue light therapy might help you sleep three hours longer.

To reduce the impact of synthetic light on our biological system, lighting manufacturers have been developing dynamic lighting control led by computer based systems. For example, to perk people up in the morning, the lamp increases the blue light concentration. After lunch, it again produces more blue light to counter afternoon sleepiness. In Europe, such systems have already been installed in some places including some hospitals, business offices, town halls and traffic-control centers.

Keeping all this in mind, we see how blue light affects our daily life. So, sleeping in some parts of the daytime can have advantages and disadvantages for sustaining optimal performance.

Daytime sleep in Prophetic tradition

If we turn our attention to the life of the Prophet Muhammad, (peace and blessings be upon him) we see how he successfully set an example for his Companions. It was the practice of the Prophet and his Companions not to sleep after the dawn prayer, the first of the five daily prayers, as it is a time of blessing. He would read some parts from the Qur’an and reflect on the universe and its Creator at a time when concentration is at its peak and the mind is clear of daily worries. Once dawn broke, the Prophet would pray and then speak with people who stayed behind for some time. Therefore, some of the early Muslims disliked the idea of sleeping immediately after dawn because being awake at this time was encouraged.

The first is “ghaylula.” This is from pre-dawn to forty minutes or so after the sun has risen, the time when prayer is lawful but reprehensible. Sleep at this time is contrary to the practices of the Prophet, since according to hadiths, it leads to a decrease in one’s livelihood and to its being unfruitful. The time most appropriate for preparing to labor for one’s sustenance is when it is cool. When this time has passed, lethargy descends. It has been established through numerous experiences that just as this is detrimental to that day’s labor and indirectly to one’s livelihood, so also is it the cause of unfruitfulness.

Based on our limited knowledge about blue light, by sleeping at this time we may cause our biological rhythms to delay because of missing the right blue intensity at the correct time, which can result in a shift in sleep period and other shifts in daily cycles.

The second is “faylula.” This is from the afternoon prayer till sunset. This sleep leads to a diminution of life, that is, it makes life that day shorter and makes it pass in a state of semi-sleep due to drowsiness, thus causing a physical deficiency to life. So too in an immaterial aspect, since most of the results of that day, material and immaterial, become apparent after the afternoon prayer, to pass that time in sleep as though prevents those results being seen and makes the day as though not lived.

The third is “qaylula,” which is in accordance with the Sunna of the Prophet. It is from mid-morning to just past noon. This sleep is part of the Sunna since it allows a person to rise at night to pray. So also in the Arabian Peninsula to rest from work at noon when it is intensely hot is the custom of the people and of the area, so has further strengthened this Practice of the Prophet. This sleep increases both life and sustenance. For half an hour’s qaylula sleep is the equivalent of two hours’ sleep at night. That means it adds one and a half hours to a person’s life every day. It saves one and a half hours from the hand of sleep, the brother of death, and makes it live, adding it to the time of working for one’s livelihood.

Recently, this type of sleep or nap has been strongly advised for health and for enhancing daily performance. “When I was at NASA we gave the pilots a planned nap in the cockpit,” says Rosekind, a board member of the National Sleep Foundation. “While two pilots flew the plane, the third would have forty minutes to nap. We found they would sleep for twenty-six minutes, which boosted their performance by 34% and their alertness by 54%.”9 He explains that the pilots were able to improve their performance significantly, and he adds that the effects of a short nap of less than a half hour lasted for two to three hours. Similar research shows that in this way you can make yourself more alert, reduce stress, and improve cognitive functioning, which means more patience, less stress, better reaction time, increased learning, and more efficiency.

Each day our daily life gets faster and we unintentionally ignore our body and its need for rest, which leads to sleep deprived eyes, disturbed sleep cycles, stress, and so on. Sleeping well keeps us alive longer. But this does not mean sleeping for a long time, which increases the risk of death. What we learn from the Prophetic tradition and research into the effects of light on our biological clocks can help us to find and to arrange proper times for sleeping and coordinating our daily activities. Once we achieve this, benefits in spiritual life, health, social interactions, learning and thinking clearly will follow.

[souvik5002]

Origin of Light

Solar energy results from nuclear fusion in the sun’s core, which creates an enormous, continuous flow of radiant energy that travels through- out the solar system. The energy that reaches us from all the stars twinkling in our galaxy can- not compare with what we receive from the sun, the only significant source of energy for Earth’s atmosphere.

This radiant energy released in the form of electromagnetic waves, which travel unimpeded from the sun in straight lines at the speed of light-186,000 miles a second. Although the intensity of the energy diminishes as it travels the 93 million miles from the sun to Earth’s

outer atmosphere, the amount of energy received by Earth from the sun in ten seconds still is equivalent to all the electricity generated on the planet in one week. Electromagnetic waves vary in length, which is measured as the distance between the crests of waves

Different types of Light

All the types of these waves together constitute the electromagnetic spectrum, which ranges from extremely short ultraviolet waves to very long radio waves. Visible light, which occupies a narrow band of that spectrum, comprises colors that vary in wavelength from short to long.

Shorter wavelengths scatter more effectively in the atmosphere, which is why the sky is blue-a color with a relatively short wavelength-on a sunny day. At dawn and dusk, light must pass through more atmosphere, allowing the longer orange and red light waves to predominate over the widely scattered blue waves.

The multicolored arc of a rainbow is produced by sunlight striking raindrops beneath a rain cloud. Light refracts-bends-when it passes through drops of water. Each color of light refracts at a different angle: Violet bends more than blue, which bends more than green, and so on, with red refracting the least. If sunlight enters a raindrop at just the proper angle, it refracts, and its many colors spread into a visible array.

Sunlight refracted through millions of raindrops forms a rainbow. On a primary rainbow, red is the outside color and violet the inside color. Occasionally a secondary rain- bow appears slightly higher in the sky, and in it the colors of the rainbow are reversed (opposite). A rainbow’s position in the sky depends on the sun’s altitude above the horizon-the lower the sun, the higher the rainbow appears.

For more read click here:  https://shouts.site/light/

[schmidtclothingcom]

White Sunblock is a Thing of the Past

by Joel Pedersen

As a child, I spent many summer days at the beach in southern California. I remember playing in the surf, collecting shells, watching sea lions, and seeing the white noses of the lifeguards. In those days, lifeguards smeared thick, white zinc oxide paste on their noses to protect themselves from getting sunburned

My nose, smeared in Zinka Sunblock, which contains zinc oxide particles

When my kids were young there was a brief period when colored zinc oxide sunblock seemed to be in vogue

My nose, smeared in colored Zinka Sunblock

Nowadays, we still use zinc oxide in sunblocks, but it’s no longer white or colored; it’s transparent! How can this be? It’s the same material!!

My nose, smeared in Blue Lizard sunblock, which contains zinc oxide nanoparticles

White pasty sunblocks protect your skin by absorbing and scattering away the harmful ultraviolet radiation. They also happen to scatter the less energetic form of radiation, visible light. They appear white in color because they scatter all colors of visible light roughly equally, so the white light that hits the sunblock is still white light when it hits our eyes. The colored sunblocks had pigments added that absorb some wavelengths of visible light.

Nano-enabled zinc oxide sunblock appears transparent because the smaller particles in it do not scatter light as effectively as their larger pasty counterparts. This might seem like a problem. If they don’t scatter light as effectively, wouldn’t that mean they would allow more harmful ultraviolet radiation through to your skin, unscattered? In fact, they do not! But I’m getting ahead of myself. First, let’s discuss why nano-sized zinc oxide particles are transparent while the larger sized particles in the older sunblocks appear white.

Different particle sizes scatter light to varying degrees.(1) As particles become so small that their diameters are equivalent to roughly half the wavelength of light, the intensity of scattered light falls steeply. This means, if you can make particles smaller than about half the wavelength of visible light (390 to 700 nanometers), they will no longer be able to scatter that visible light efficiently! So, nanoparticles smaller than roughly 200 nanometers are practically transparent.

Now that we’ve solved the problem of light scattering by zinc oxide particles in sunblock, let’s return to our earlier question. By making particles that don’t scatter visible light, have we created another problem? Aren’t we allowing harmful ultraviolet radiation to reach the skin on the lifeguards’ noses since we’re not scattering it away. Fortunately not! Nano-scale zinc oxide remains effective in sunblock because it efficiently absorbs ultraviolet light, preventing it from interacting with the skin.

Light scattering also depends on wavelength. For particles much smaller than the wavelength of light, those particles scatter shorter wavelength light (for example UV light) much more efficiently than longer wavelength light (for example, visible light). More precisely, for particles in this size range, scattering is inversely proportional to the fourth power of the wavelength. This means that UV light at, say, 350 nanometers is scattered nearly 5× more efficiently than green light at 520 nanometers, all else being equal. (The wavelength-dependent scattering is the reason the sky is blue, but I digress.)

In conclusion, we have seen that for scattering light, size matters! Zinc oxide nanoparticles can be made in sizes smaller that approximately 200 nanometers, so we no longer have to smear unsightly white paste on our noses to take advantage of the sun-protective effect of zinc oxide.

  Shop Schmidt Clothing for all your summer clothing

  // <![CDATA[ (function () { var scriptURL = 'https://sdks.shopifycdn.com/buy-button/latest/buy-button-storefront.min.js'; if (window.ShopifyBuy) { if (window.ShopifyBuy.UI) { ShopifyBuyInit(); } else { loadScript(); } } else { loadScript(); } function loadScript() { var script = document.createElement('script'); script.async = true; script.src = scriptURL; (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(script); script.onload = ShopifyBuyInit; } function ShopifyBuyInit() { var client = ShopifyBuy.buildClient({ domain: 'schmidt-clothing.myshopify.com', storefrontAccessToken: '04e3f2c2f256c599ae4e274d76cc6246', }); ShopifyBuy.UI.onReady(client).then(function (ui) { ui.createComponent('collection', { id: '188621521034', node: document.getElementById('collection-component-1593789762986'), moneyFormat: '%24%7B%7Bamount%7D%7D', options: { "product": { "styles": { "product": { "@media (min-width: 601px)": { "max-width": "calc(25% - 20px)", "margin-left": "20px", "margin-bottom": "50px", "width": "calc(25% - 20px)" }, "img": { "height": "calc(100% - 15px)", "position": "absolute", "left": "0", "right": "0", "top": "0" }, "imgWrapper": { "padding-top": "calc(75% + 15px)", "position": "relative", "height": "0" } }, "button": { ":hover": { "background-color": "#0363b3" }, "background-color": "#023a69", ":focus": { "background-color": "#0363b3" }, "border-radius": "14px", "padding-left": "46px", "padding-right": "46px" } }, "buttonDestination": "checkout", "text": { "button": "Buy now" } }, "productSet": { "styles": { "products": { "@media (min-width: 601px)": { "margin-left": "-20px" } } } }, "modalProduct": { "contents": { "img": false, "imgWithCarousel": true, "button": false, "buttonWithQuantity": true }, "styles": { "product": { "@media (min-width: 601px)": { "max-width": "100%", "margin-left": "0px", "margin-bottom": "0px" } }, "button": { ":hover": { "background-color": "#0363b3" }, "background-color": "#023a69", ":focus": { "background-color": "#0363b3" }, "border-radius": "14px", "padding-left": "46px", "padding-right": "46px" } }, "text": { "button": "Add to cart" } }, "cart": { "styles": { "button": { ":hover": { "background-color": "#0363b3" }, "background-color": "#023a69", ":focus": { "background-color": "#0363b3" }, "border-radius": "14px" } }, "text": { "total": "Subtotal", "button": "Checkout" } }, "toggle": { "styles": { "toggle": { "background-color": "#023a69", ":hover": { "background-color": "#0363b3" }, ":focus": { "background-color": "#0363b3" } } } } }, }); }); } })(); // ]]>

[sailorrrvenus]

Recreating the Look of 1850s Tintypes in Digital with Math and Science

While I was visiting San Francisco, Kristy Headley, a dear friend and fellow engineer, showed me her studio. There I was lucky enough to sit for her while she did some vintage tintyping. Tintyping was one of the earliest forms of photography, popular in the 1850s.

It was a kind of incredibly inconvenient Polaroid — the photos were exposed instantly after a quick wash on plates of iron or aluminum (never actually tin). All you needed was a very, very large camera, plates treated with “collodion” to make a light-reactive surface, and a sizable collection of chemicals. Unfortunately, the genuine process has a high risk of explosion, creating cyanide gas, incurring blindness from silver halide splashback, or getting whacked out on ether.

“Dusty”. Tintype/ferrotype by Quinn Jacobson and licensed under CC BY-SA 3.0

Kristy showed me each painstaking step, and I was enamored with the result. With her mastery of lighting techniques, she’d produced tintype photographs where every detail popped — every freckle, hair, and eyelash seemed to stand out. Yet, these looked very different from modern photography. There was a certain, seemingly unquantifiable trait to them. Why?

I sought out to quantify this ol’ timey look and the fashion by which one could reproduce it with a digital camera. Perhaps I could share in this delight without keeping jugs of volatile chemicals in my room.

Look to the Spectrum!

Kristy had told me that her exposure plates were only sensitive to certain colors: UV, blue, and some green. There was a specific range of wavelengths this collodion emulsion was sensitive to — one that doesn’t match human vision.

Human vision, as we can see above, is a sensitivity to the electromagnetic spectrum. Electromagnetic waves between about 400 and 700 nanometers will be perceived as light to us — the seven colors of the rainbow! (Interesting article about this to come later) If we dip to wavelengths shorter than 400, we get imperceivable ultraviolet (UV) light; rise to wavelengths above 700, we get imperceivable infrared (IR) light.

But What Do Vintage Photographic Emulsion Surfaces See?

Engineer Niles Lund seems to be the only person who has researched the spectral sensitivity of collodion, the emulsion chemical stew used to make wet-plate and tintype photographs in the mid-1800s. After exchanging a few emails, Niles sent me this updated spectral chart.

Spectral sensitivity of cadmium bromide, potassium iodide, and collodion consisting of the two. Available here.

So now we know what to recreate if we want “digital collodion”! We need to cut out the upper half of the visible spectrum allowing nothing above about 520 nanometers into the camera.

I’ve done much work in this field, so I thought this would be a great time to blend science and art to explore this concept and compare it to other hyper-spectral imagery!

Setting Up an Experiment

Now we invite some friends and models to come sit for us! I asked the models to avoid skin-concealing makeup and zinc-oxide sunscreen, which is the only sunscreen to obstruct UV-A rays. They were asked to model under a broad-spectrum light source (the sun), with an additional light source of a silver reflector, and maintain a pose for a few minutes while I photograph each under the following conditions:

Visible Spectrum

This is what humans see (obviously). Using three cones, sensitive to three different ranges of wavelengths, which loosely map to red-green-blue, we see everything from violet to red. Violet is the shortest wavelength. Red is the longest. Not surprisingly, this is what digital cameras see, as well. Silicon photovoltaic sensors, whether CCD or CMOS, can take in a theoretical 290nm to 1100nm. However, it would be maddening to have your photography overexposed, blooming, and flaring due to lightwaves you cannot see, to say nothing of threats of overheating, so sensors are limited by optical filters placed directly over the sensor to only photograph, more-or-less, in the human visible spectrum. Photons that don’t play nice in this range are either bounced back out of the lens or absorbed and destroyed.

Here’s what our model Kayla looked like in the visible spectrum:

Captured on an unmodified Nikon D610 through a normal UV-limiting 50mm lens. Notice her light freckles, dark shirt, and slightly light eyes

Orthochromatic Blue (Collodion AND Squid Vision)

This could be seen as the same spectrum that octopus and squid might view in. Humans, except for rare and awesome mutants and the colorblind, are “trichromatic”, with three cones that allow for three different ranges of wavelengths in. Cephalopods only have one, the S cone, which is sensitive in almost the exact fashion of the spectral curve of the 1850’s collodion (except for UV). Though they might have a different mechanical use of their eyes, which could allow for more color vision, but I digress…

By using Schott BG25 bandpass glass, bought off a gentleman who fits esoteric german glass into filters, on a lens that cuts UV (any normal lens) on any unmodified camera, we get a theoretical spectral sensitivity that looks like:

The “double bandpass” ionically colored glass made by Schott AG in Germany nicely mimics the spectral response of the collodion.

Of course, all the photons that this can transmit that the camera can’t capture become irrelevant, so on an unmodified camera, we will get a spectral response that looks like:

This means that on an unmodified camera, using a lens that doesn’t block UV, we’re going to get an image where the focus is going to be more on near-UV damage to the skin — concentrations of freckles and blemishes are going to much more pronounced. There’s going to be a light leak of very red photons, and we’ll be missing much of the UV range, but we’re very close to vintage emulsion now.

Our model, under the same lighting conditions (with an exposure compensation of +.7, calibrated from an 18% gray card):

Captured on an unmodified Nikon D610 through a UV-permitting 50mm lens and a BG25 double bandpass filter. Notice her pronounced freckles, dark shirt, and very light eyes

By gum, we’ve done it! With that nanty narking, I think we can say we’ve captured the ol’ timey feel of collodion!

…but it is not scientifically accurate. This is about the best we can do on an unmodified camera, as we need some expensive modifications to allow UV to extend into the sensor. More on that later.

Let’s see what she looks like in some other, more bizarre wavelengths!

Near Infrared and Short Wave Infrared (Snake Vision)

This is, likely, what snakes see. This is the orange-and-red human-visible spectrum (near infrared, or NIR) and the infrared waves closer to the human spectrum. This is what I like to photograph foliage in because it can be false-colored and remapped using the color channels that your camera knows how to deliver data in. I have a Nikon D80 that has been modified to shoot in this wavelength, with an upper infrared spectrum bound (unmeasured) limited only by the physical limitations of a silicon CCD.

For some reason, for the duration of this experiment, this setup absolutely refused to focus properly. This camera does not have live-view, and it is very difficult to assess these images until they’ve been processed on a computer. Nonetheless, these blurry images were interesting…

Captured on a modified Nikon D80 through normal 50mm lens, no filter. Notice there are no freckles, and her shirt appears grey.

Short Wave Infrared

I don’t think anything “sees” solely in this spectrum, though it is a difficult concept to explore, so perhaps time will tell. To capture the full breadth of short wave infrared, or to move into longer wave infrared, we would have to use a special sensor made out of indium gallium arsenide. It’s interesting to see that any sun damage and melanin deposits, such as freckles and tans, will not appear in this wavelength. The IR photons do a good deal more sub-surface scattering in the skin than visible light, rendering each person as a waxen figure.

Captured on a modified Nikon D80 through a normal 50mm lens and a BG25 double bandpass filter. Notice there are no freckles, her shirt now appears white, her eyes have darkened considerably, and all of her skin appears waxen and soft.

Polishing these photos up a bit in a vintage style split-toning

You might have noticed these are not delivered in monochromatic black and white, as in the style of a silver gelatin process. Instead, I chose to render them out with a bit of split-toning. Since the birth of photography, this was a common practice, using various methods to bring color to the highlights and to the shadows.

In this case, I made the highlights gold to mimic the flame-gilding of the mid-1800s, which “fixed” the highlights of a photograph using a gold chloride solution and an open flame. As ambrotypes caught on in the 1860s, “ruby” hued backs became more common in photography, so I enjoy using a red tint in my lowlights.

Photo Results

Kaitlin

Visible

Collodion

Kevin

Visible

Collodion

Christine

Visible

Collodion

Xach

Visible

Collodion

Caitlin

Visible

Collodion

Kayla

Visible

Collodion

Next Steps to Take it Further

In order to fully and accurately capture the collodion sensitivity range, I need to not only use a lens that allows ultraviolet photons to pass, as used in this experiment, but also a camera with a sensor modified to receive UV light. Because this is not a fast or cheap prospect, I’ve been dragging my feet to see if this could be done in conjunction with another modification…

As photographing humans draws no benefit from presenting false color, hyperspectral photography (such as UV) is best delivered in black and white. Having a color sensor actually hurts collodion-spectrum portraiture — if the construction of the image relies on a missing red channel, then we need to have a monochromatic sensor to gather an image using the filters described in this process with due sharpness.

We have different options: Buy a monochromatic camera, which can run between 3,000 and 50,000 dollars, or do a “mono-mod” to scrape the Bayer filter off of an existing camera. Conversion shops have assured me this is impossible on the Nikon cameras that I like to use, but I hold out hope for a “full spectrum” monochromatic modification. Alternatively, I can also look into intelligent upscaling, possibly using AI to regain resolution lost in the process.

Final Thoughts

As I used attractive models in this experiment, instead of the lab tools one should use to characterize optics, the spectral range of each photograph is an educated guess at best, based on theoretical readings. Lab characterizations will follow.

Trust the math. I know things look underexposed and incorrect, but if you’ve set your exposure compensation based off an 18% gray card — or, realistically, ignored that and just set it to +.7, then you can trust your lightmeter shooting in “orthochromatic blue”.

Sometimes, there’s no substitute for the real thing — recreating wet-plate collodion and tintypes is severely limited by digital consideration — but limitation is the mother of invention!

Editor’s note: A longer and more comprehensive version of this article can be found on Warren’s website. In it, Warren also discusses challenges he encountered with Bayer filters and how he wrote his own demosaic algorithm script to overcome them.

About the author: Phil Warren is a photographer, engineer, explorer, and adventurer. The opinions expressed in this article are solely those of the author. You can find more of Warren’s work and writing on his website and Instagram.

source https://petapixel.com/2019/04/05/recreating-the-look-of-1850s-tintypes-in-digital-with-math-and-science/

[pauldeckerus]

Recreating the Look of 1850s Tintypes in Digital with Math and Science

While I was visiting San Francisco, Kristy Headley, a dear friend and fellow engineer, showed me her studio. There I was lucky enough to sit for her while she did some vintage tintyping. Tintyping was one of the earliest forms of photography, popular in the 1850s.

It was a kind of incredibly inconvenient Polaroid — the photos were exposed instantly after a quick wash on plates of iron or aluminum (never actually tin). All you needed was a very, very large camera, plates treated with “collodion” to make a light-reactive surface, and a sizable collection of chemicals. Unfortunately, the genuine process has a high risk of explosion, creating cyanide gas, incurring blindness from silver halide splashback, or getting whacked out on ether.

“Dusty”. Tintype/ferrotype by Quinn Jacobson and licensed under CC BY-SA 3.0

Kristy showed me each painstaking step, and I was enamored with the result. With her mastery of lighting techniques, she’d produced tintype photographs where every detail popped — every freckle, hair, and eyelash seemed to stand out. Yet, these looked very different from modern photography. There was a certain, seemingly unquantifiable trait to them. Why?

I sought out to quantify this ol’ timey look and the fashion by which one could reproduce it with a digital camera. Perhaps I could share in this delight without keeping jugs of volatile chemicals in my room.

Look to the Spectrum!

Kristy had told me that her exposure plates were only sensitive to certain colors: UV, blue, and some green. There was a specific range of wavelengths this collodion emulsion was sensitive to — one that doesn’t match human vision.

Human vision, as we can see above, is a sensitivity to the electromagnetic spectrum. Electromagnetic waves between about 400 and 700 nanometers will be perceived as light to us — the seven colors of the rainbow! (Interesting article about this to come later) If we dip to wavelengths shorter than 400, we get imperceivable ultraviolet (UV) light; rise to wavelengths above 700, we get imperceivable infrared (IR) light.

But What Do Vintage Photographic Emulsion Surfaces See?

Engineer Niles Lund seems to be the only person who has researched the spectral sensitivity of collodion, the emulsion chemical stew used to make wet-plate and tintype photographs in the mid-1800s. After exchanging a few emails, Niles sent me this updated spectral chart.

Spectral sensitivity of cadmium bromide, potassium iodide, and collodion consisting of the two. Available here.

So now we know what to recreate if we want “digital collodion”! We need to cut out the upper half of the visible spectrum allowing nothing above about 520 nanometers into the camera.

I’ve done much work in this field, so I thought this would be a great time to blend science and art to explore this concept and compare it to other hyper-spectral imagery!

Setting Up an Experiment

Now we invite some friends and models to come sit for us! I asked the models to avoid skin-concealing makeup and zinc-oxide sunscreen, which is the only sunscreen to obstruct UV-A rays. They were asked to model under a broad-spectrum light source (the sun), with an additional light source of a silver reflector, and maintain a pose for a few minutes while I photograph each under the following conditions:

Visible Spectrum

This is what humans see (obviously). Using three cones, sensitive to three different ranges of wavelengths, which loosely map to red-green-blue, we see everything from violet to red. Violet is the shortest wavelength. Red is the longest. Not surprisingly, this is what digital cameras see, as well. Silicon photovoltaic sensors, whether CCD or CMOS, can take in a theoretical 290nm to 1100nm. However, it would be maddening to have your photography overexposed, blooming, and flaring due to lightwaves you cannot see, to say nothing of threats of overheating, so sensors are limited by optical filters placed directly over the sensor to only photograph, more-or-less, in the human visible spectrum. Photons that don’t play nice in this range are either bounced back out of the lens or absorbed and destroyed.

Here’s what our model Kayla looked like in the visible spectrum:

Captured on an unmodified Nikon D610 through a normal UV-limiting 50mm lens. Notice her light freckles, dark shirt, and slightly light eyes

Orthochromatic Blue (Collodion AND Squid Vision)

This could be seen as the same spectrum that octopus and squid might view in. Humans, except for rare and awesome mutants and the colorblind, are “trichromatic”, with three cones that allow for three different ranges of wavelengths in. Cephalopods only have one, the S cone, which is sensitive in almost the exact fashion of the spectral curve of the 1850’s collodion (except for UV). Though they might have a different mechanical use of their eyes, which could allow for more color vision, but I digress…

By using Schott BG25 bandpass glass, bought off a gentleman who fits esoteric german glass into filters, on a lens that cuts UV (any normal lens) on any unmodified camera, we get a theoretical spectral sensitivity that looks like:

The “double bandpass” ionically colored glass made by Schott AG in Germany nicely mimics the spectral response of the collodion.

Of course, all the photons that this can transmit that the camera can’t capture become irrelevant, so on an unmodified camera, we will get a spectral response that looks like:

This means that on an unmodified camera, using a lens that doesn’t block UV, we’re going to get an image where the focus is going to be more on near-UV damage to the skin — concentrations of freckles and blemishes are going to much more pronounced. There’s going to be a light leak of very red photons, and we’ll be missing much of the UV range, but we’re very close to vintage emulsion now.

Our model, under the same lighting conditions (with an exposure compensation of +.7, calibrated from an 18% gray card):

Captured on an unmodified Nikon D610 through a UV-permitting 50mm lens and a BG25 double bandpass filter. Notice her pronounced freckles, dark shirt, and very light eyes

By gum, we’ve done it! With that nanty narking, I think we can say we’ve captured the ol’ timey feel of collodion!

…but it is not scientifically accurate. This is about the best we can do on an unmodified camera, as we need some expensive modifications to allow UV to extend into the sensor. More on that later.

Let’s see what she looks like in some other, more bizarre wavelengths!

Near Infrared and Short Wave Infrared (Snake Vision)

This is, likely, what snakes see. This is the orange-and-red human-visible spectrum (near infrared, or NIR) and the infrared waves closer to the human spectrum. This is what I like to photograph foliage in because it can be false-colored and remapped using the color channels that your camera knows how to deliver data in. I have a Nikon D80 that has been modified to shoot in this wavelength, with an upper infrared spectrum bound (unmeasured) limited only by the physical limitations of a silicon CCD.

For some reason, for the duration of this experiment, this setup absolutely refused to focus properly. This camera does not have live-view, and it is very difficult to assess these images until they’ve been processed on a computer. Nonetheless, these blurry images were interesting…

Captured on a modified Nikon D80 through normal 50mm lens, no filter. Notice there are no freckles, and her shirt appears grey.

Short Wave Infrared

I don’t think anything “sees” solely in this spectrum, though it is a difficult concept to explore, so perhaps time will tell. To capture the full breadth of short wave infrared, or to move into longer wave infrared, we would have to use a special sensor made out of indium gallium arsenide. It’s interesting to see that any sun damage and melanin deposits, such as freckles and tans, will not appear in this wavelength. The IR photons do a good deal more sub-surface scattering in the skin than visible light, rendering each person as a waxen figure.

Captured on a modified Nikon D80 through a normal 50mm lens and a BG25 double bandpass filter. Notice there are no freckles, her shirt now appears white, her eyes have darkened considerably, and all of her skin appears waxen and soft.

Polishing these photos up a bit in a vintage style split-toning

You might have noticed these are not delivered in monochromatic black and white, as in the style of a silver gelatin process. Instead, I chose to render them out with a bit of split-toning. Since the birth of photography, this was a common practice, using various methods to bring color to the highlights and to the shadows.

In this case, I made the highlights gold to mimic the flame-gilding of the mid-1800s, which “fixed” the highlights of a photograph using a gold chloride solution and an open flame. As ambrotypes caught on in the 1860s, “ruby” hued backs became more common in photography, so I enjoy using a red tint in my lowlights.

Photo Results

Kaitlin

Visible

Collodion

Kevin

Visible

Collodion

Christine

Visible

Collodion

Xach

Visible

Collodion

Caitlin

Visible

Collodion

Kayla

Visible

Collodion

Next Steps to Take it Further

In order to fully and accurately capture the collodion sensitivity range, I need to not only use a lens that allows ultraviolet photons to pass, as used in this experiment, but also a camera with a sensor modified to receive UV light. Because this is not a fast or cheap prospect, I’ve been dragging my feet to see if this could be done in conjunction with another modification…

As photographing humans draws no benefit from presenting false color, hyperspectral photography (such as UV) is best delivered in black and white. Having a color sensor actually hurts collodion-spectrum portraiture — if the construction of the image relies on a missing red channel, then we need to have a monochromatic sensor to gather an image using the filters described in this process with due sharpness.

We have different options: Buy a monochromatic camera, which can run between 3,000 and 50,000 dollars, or do a “mono-mod” to scrape the Bayer filter off of an existing camera. Conversion shops have assured me this is impossible on the Nikon cameras that I like to use, but I hold out hope for a “full spectrum” monochromatic modification. Alternatively, I can also look into intelligent upscaling, possibly using AI to regain resolution lost in the process.

Final Thoughts

As I used attractive models in this experiment, instead of the lab tools one should use to characterize optics, the spectral range of each photograph is an educated guess at best, based on theoretical readings. Lab characterizations will follow.

Trust the math. I know things look underexposed and incorrect, but if you’ve set your exposure compensation based off an 18% gray card — or, realistically, ignored that and just set it to +.7, then you can trust your lightmeter shooting in “orthochromatic blue”.

Sometimes, there’s no substitute for the real thing — recreating wet-plate collodion and tintypes is severely limited by digital consideration — but limitation is the mother of invention!

Editor’s note: A longer and more comprehensive version of this article can be found on Warren’s website. In it, Warren also discusses challenges he encountered with Bayer filters and how he wrote his own demosaic algorithm script to overcome them.

About the author: Phil Warren is a photographer, engineer, explorer, and adventurer. The opinions expressed in this article are solely those of the author. You can find more of Warren’s work and writing on his website and Instagram.

from Photography News https://petapixel.com/2019/04/05/recreating-the-look-of-1850s-tintypes-in-digital-with-math-and-science/