Anthotype - Update

I removed the step tablet from my second anthotype that was in the window for two weeks. Not only has the overall color lightened from longer exposure but there is also a greater difference between the shadow and highlight ends. The "steps" can't be seen but there is a stronger gradient.

Camera Obscura and Camera Lucida

Philosophers and scholars such as Mo-Ti in the 5^th century BCE and Aristotle in the next century observed and described the phenomenon of light passing through a pinhole to produce an inverted image. Alhazen in the 10^th century further observed that the image being projected becomes sharper or softer based on the size of the aperture. The concept of the camera obscura, Latin for “dark room,” came about during the Renaissance to control this phenomenon of light passing through an aperture. “Daguerre's suggestion that art could achieve the goal [of reproducing images of nature without drawing] points to the fact that the camera obscura was a widely used drawing aid at the time. Therefore, photography could be seen as the climax of the development of drawing aids, which began in the Renaissance” (Gasser 12).

The camera obscura improved throughout the next few centuries as lenses sharpened the image and mirrors corrected the inverted image and projected it onto a more convenient surface for artists. The basic lens type used was an achromatic doublet with both convex and concave lenses. This cancelled out chromatic aberration, in which different wavelengths of light have different focal lengths. In a pinhole camera, the light passes through the aperture and projects onto whatever surface is beyond the aperture. With the addition of a lens, the light is transmitted and refracted at angles that will cause the light to converge and focus at a specific spot. This means that the surface the image is being projected onto has to be at that focal point, unlike a pinhole camera in which the location of the surface wasn’t critical. The use of a lens brightened and sharpened the projected image. This benefited both scientists and artists as it improved a device for “aiding graphic representation and for ascertaining basic truths about nature” (Rosenblum 192).

The interest of artists to accurately translate the visible world to a graphic representation led to the invention of other devices such as the camera lucida, Latin for “light room,” which was patented by William Hyde Wollaston in 1807. Unlike the camera obscura, the camera lucida doesn’t require specific lighting conditions and it doesn’t project an image. Instead it allows the artist to view the subject and drawing surface simultaneously. It is constructed of a prism and lens on a stand, but with the addition of a mirror, the image becomes right side up and is corrected left to right.

Gasser, Martin. “Between “From Today, Painting is Dead” and “How the Sun Became a Painter:” A Close Look At Reactions To Photography in Paris 1839-1853.” Image 33, no. 3 (1991): 9-30.

Rosenblum, Naomi. A World History of Photography. New York: Abbeville Press, 1997.

A camera obscura box with a mirror and a large walk-in camera obscura in San Francisco.

 

A diagram of a camera lucida.

The suggestion that Dutch artists Johannes Vermeer used a camera obscura to obtain the remarkable detail in his paintings remains controversial.

http://www.essentialvermeer.com/camera_obscura/co_one.html

For my camera obscura, I used a double convex glass lens instead of the plastic magnifying lens from class. Light traveling parallel to the lens axis passes through and converges at a spot behind the lens. The distance between the lens and this spot where the image is in focus is called the focal length.

To make my camera obscura, I used two boxes. Because one was bigger than the other by about an inch, I put extra cardboard in the bottom to make the smaller Life box fit. I cut off the ends of the Life box.

I cut a hole the size of my lens in the bottom of the larger box and taped the edges of the lens so it sat over the hole.

 

The focal lengths I found were 6.75in to 7.25in depending on the distance between the object and camera obscura so I cut the Life box down to 6.5in so the focus could be adjustable. I taped wax paper over one open end of the Life box.

I added strips of cardboard to the sides of the Life box to make pushing or pulling the box easier for focusing.

 Right-side-up image of plants in a pot.

 Right-side-up image of a pillow on a couch.

Making the camera obscura was a lot easier than I thought it would be. I’m glad I made it adjustable because it’s cool to be able to focus on distant or nearby objects. The focus is also sharper than I was expecting it to be.

Photographer Abelardo Morell works extensively with camera obscuras. He has used tent-cameras that project images of his surroundings onto the ground which he then photographs, and he uses small and room-sized camera obscuras with amazing detail.

He also photographed the crescent shape of a partially eclipsed sun projected onto the ground through holes in leaves, much like what Aristotle observed in the 4^th century BCE.

Photogenic Drawing on Salted Paper with Hypo

Talbot’s salted paper process was a printed-out process (POP) meaning the photographs were developed in the sun. The photographs are made by coating paper with a weak salt solution, drying, and coating with silver nitrate, which reacts to additives already in the paper. Salted paper prints have a matte texture and soft image that appealed to a portion of the population despite never achieving commercial success.

Talbot found that potassium iodide (KI) stabilized the image, but it has the tendency to bleach the metallic silver that forms the image. He found that sodium chloride, or salt, gave the best results as a stabilizer by reducing the paper’s sensitivity to light. He changed to sodium thiosulphate, or hypo, in 1839 when it was discovered by his friend and scientist John Herschel. The addition of hypo made Talbot’s “photogenic drawing” paper evolve into what was known as “plain salted paper.”

The sizes of silver particles in printed-out images are smaller than “wavelengths of visible light which leads to a combination of scattered and transmitted light” (Goins). Smaller particles transmit warmer colors, such as yellow and red, and scatter cooler colors, such as blue and green. Therefore, the tiny, or “colloidal,” particles in Talbot’s photogenic drawings and salted paper prints give his printed out images a warm tone. Hypo works by removing the silver chloride from the matrix, which will then shift the refractive index from 2.071 of silver chloride to the refractive index of silver hydrosol (usually close to 1.0). This shifts the absorption band to lower wavelengths, causing images to look yellow-brown and duller. As the prints dry and the image layer contracts, they become more neutral in color and gain slight density.

Goins, Elizabeth, first draft of chapter

Rosenblum, Naomi. A World History of Photography. New York: Abbeville Press, 1997.

Reilly, James M. The Albumen & Salted Paper Book: The history and practice of photographic printing, 1840-1895. Light Impressions Corporation. Rochester, 1980. <http://albumen.conservation-us.org/library/monographs/reilly/chap9.html>

http://www.alternativephotography.com/wp/pop-printing-out-process/printing-out-processes

http://albumen.conservation-us.org/library/monographs/reilly/chap3.html

We concluded from the results of our previous photogenic drawing experiment that 2 coats of 12% sliver nitrate (AgNO3) over one coat of salt solution (NaCl) on Strathmore cold press watercolor paper yielded the best tonal variation. Therefore, we used this process to coat our paper that we exposed with color filters and objects.

We cut the letters “R”, “B”, and “Y” out of red, blue, and yellow cellophane to place on a half sheet of paper to test the effect of color negatives on image formation. Our hypothesis was that the silver emulsion would be more sensitive to blue (shorter) wavelengths than red or yellow (longer) wavelengths.

Four sheets of paper had objects placed on them and the fifth sheet had the “R”, “B”, and “Y” cellophane. They were exposed in the sun for about 3 minutes until they turned a dark grey.

The papers were placed in a water wash, two sodium thiosulphate (hypo) baths, and then a final water wash to fix the images. The images became a yellowish brown and slightly lightened once under the hypo. The color cellophane and Peter’s objects were the only papers exposed under glass and it was interesting to find that they turned out darker than the other three that were exposed with no glass.

The paper beneath the blue “B” was completely darkened while the areas under the “R” and “Y” remained light. The paper under the “B” was dark because light got through the cellophane to the silver emulsion. The only wavelengths that are transmitted through blue cellophane are short wavelengths, or the blue end of the spectrum. Therefore, our hypothesis that the silver emulsion is more sensitive to blue (shorter) wavelengths was correct.

I used a beaded necklace for my salted paper print and although it darkened to a deep purple-grey under the sun, it lightened and turned a yellowish brown under the water and hypo baths. I let my image sit in a water bath for about an hour at my apartment and it seemed to gain contrast and turn to a redder brown. There are very distinct highlights where the beads were touching the paper since the light couldn’t expose that section of the paper.

 




Albumen and Salt Paper group on Flickr:

http://www.flickr.com/groups/1335034@N20/

http://www.flickr.com/photos/hillyfaekillie/5549978731/in/pool-albumen#/photos/hillyfaekillie/5549978731/in/pool-1335034@N20/

http://www.flickr.com/photos/yourmung/5170594181/