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What Secrets Did the Photographer Know?

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Major J. A. Philpott, Commandi... Major J. A. Philpott, Commanding Officer of the 490th Bomb Squadron, 341st Bomb Group and crew pose beside their plane at Ondal Airfield, India. 15 March 1943.
In mid-March of 1943, an unnamed US Army photographer visited Ondal Air Base, then under construction northwest of Calcutta in British India. He was a combat photographer with the 10th AAF Combat Camera Unit, but this was a noncombat project: accompanying an American Red Cross team as they opened “Club 690” for the base’s enlisted men. The photographer’s assignment, it seems, was to obtain pictures appropriate for release through US newspapers to inspire and reassure the American public. He completed that assignment, capturing newspaper-ready photos of heroic bomber crews, hard-working mechanics and more. He took other photos as well, some showing less pleasant realities of an American military base in colonial India. Twenty-six of his Ondal photographs (together with brief notes about each) are preserved in the US National Archives. Eighteen of the photos are available at https://www.hoosierscientist.com/ondalphotos

All wartime bases hold secrets. Some secrets involve military tactics, such as the struggle by B-25 bomber crews to find an effective technique for destroying the bridges they targeted in Burma. Other secrets were related to propaganda, such as the colonial government’s claim there was no shortage of food at a time when the price of rice was rising dramatically and the region was on the verge of a devastating famine. Ondal’s biggest secret in March of 1943, however, was both local and broadly strategic. The US was developing Ondal not just as a base for medium-range B-25 bombers but also as the site of Ondal Advanced Chemical Park. By early 1945, Ondal ACP would house a stockpile of nearly 100,000 mustard, phosgene, cyanogen chloride and other chemical bombs that could have been—but never were—delivered to the Japanese home islands on long-range B-29 bombers operating through China.

Which secrets, if any, do you think the photographer knew when he took his photos at Ondal?

Fred Thomas
aka: A Hoosier Scientist
http://www.hoosierscientist.com
#WW2bombs #airforcehistory #asianhistory #buriedbombs #cbitheater #chemicalwarfare #chemicalweapons #presidenttruman #steameducation #stemeducation

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How Did the First Color Photo Show Red, If the Film Was Not Sensitive to Red Light?

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The First Permanent, "Full-Col... The First Permanent, "Full-Color" Photograph, Displayed by James Clerk Maxwell in 1861
The Maxwell-Sutton photograph of a tartan ribbon is considered the first permanent color image ever captured. Maxwell displayed the image as a set of overlaid projections of grayscale images which were captured and displayed through red, green and blue filters. The 3 original transparencies still exist, along with a fourth transparency captured through a yellow filter that Maxwell did not use in his presentation.

The frequently displayed reproduction above was actually produced in 1940 in a effort to better understand the scientific and technical origins of color photography. The reproduction drew attention to the fact that photographic chemicals available in 1861 were completely insensitive to the low-energy photons of red light--and yet the photo clearly shows red. Sutton's documentation of his process shows he found it easiest to capture an image through a blue filter, which corresponds to the maximum sensitivity of his chemicals. He found he needed a much longer exposure with his green filter, corresponding to the lower sensitivity of the chemicals. He reported that the red image required less exposure time than did the green. The 1940 researchers found another clue in that the red image is slightly out of focus, despite the care taken by Sutton as he used his red-sensitive eyes to focus the red image.

Let us know how you think an image taken in bright sunlight through a red filter can show shades of red--when the chemicals were NOT sensitive to red photons.

Let us know too if you have ideas for other "Questions Worth Considering" as ways to better connect science, technology, engineering, art and may.

Fred Thomas
aka: A Hoosier Scientist
http://www.hoosierscientist.com
#colorphotography #jamesclerkmaxwell #photography #rgb #steameducation #stemeducation #thomassutton

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Are RGB Digital Cameras Becoming Obsolete?

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Current filter arrays use 9 pix... Current filter arrays use 9 pixels to evaluate R, G and B color intensities for each pixel. An alternative L*a*b* array could use 4 pixels to capture all the needed data for each intersection. Stare at a blue spot for 20 se... Stare at a blue spot for 20 seconds, then look at a white background. Do you see the yellowish afterimage Hering predicts?
The RGB (red-green-blue) system of color imaging is so well established that it may seem to be the only option. There are practical and theoretical reasons, however, to consider whether RBG cameras might soon become obsolete. The RGB or ("trichromatic") system dates back to the first ever color photograph, taken with grey-scale film using red, green and blue filters by physicist, James Clerk Maxwell, and photographer, Thomas Sutton, in 1852. Then and now, the system successfully fools humans into believing they see all colors of the spectrum when they are actually seeing different combinations of red, green and blue. A spectrometer, for example, readily distinguishes a combination of red and green from true yellow, but humans cannot.

Modern digital cameras still use an array of red, green and blue filters to record light intensities onto a broad-spectrum sensor. A 4 MB camera generally does have 4,000,000 locations for which to record light intensity, but 1 million are captured through red filters, 2 million through green filters, and 1 million through blue filters. The camera's electronics CALCULATE separate red, green and blue intensities for each of the 4 million pixels, but do so by interpolating values for adjoining pixels. Each pixel's color data actually incorporates data from NINE (9) pixels.

Way back in 1892, physiologist Ewald Hering offered an alternative theory of human color vision, called "Opponent Process Theory." He cited experiments which trichromatic theory could not explain, including "afterimages" which linger in our field of view. If we stare at a blue spot for 20 seconds, for example, then look at a white background, we generally see a yellowish afterimage. To explain these observations, Hering suggested that the information transmitted to our brains is NOT the full set of RGB intensities, but rather a red-green comparison (a*), a yellow-blue comparison (b*) and a measure of overall brightness (L*).

Herring's theory lives on. Most modern experts believe that trichromatic theory does provide an accurate description of how our EYES function, but that Herring's theory provides a better description of how our BRAINS actually interpret color. Herring's L*a*b* system is sufficiently well established that it is available in programs such as Photoshop as an alternative method for manipulating color images.

Display devices such as TVs and computer monitors do need to produce images that match the functioning of the human eye, so they may always need to use RGB displays. There is no fundamental reason, however, that cameras need to capture all the same data our eyes capture and then discard. Cameras could capture values for L*, a* and b* directly--and the result might be both better color quality and better spatial resolution.

Will RGB digital cameras really become obsolete? Maybe, maybe not. But it is a question worth considering--and that's what our website is all about.

Fred Thomas
aka: A Hoosier Scientist
http://www.hoosierscientist.com/rgb-obsolete
#Hering #colorvision #opponentprocess #photography #rgb #steameducation #stemeducation #trichromatic

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