The Physics and Art of Photography, Volume 2: Energy and color by John Beaver

Author:John Beaver
Language: eng
Format: epub
ISBN: 9781643273440
Publisher: IOP Publishing
Published: 2018-11-21T00:00:00+00:00

The accelerator turns out to be very simple—water alone has a large effect. An oxygen scavenger such as ascorbic acid (vitamin C), and a binder (such as xanthan gum) to make the solution brush more readily are all the rest that is needed. More information on the choice of paper and recipes for the accelerator can be found in appendix C of this volume. The physical mechanism behind the action of the accelerator is discussed in Volume 3 of The Physics and Art of Photography.

And so we have the best of both worlds. We brush the accelerator onto the paper immediately before exposure in order to render it sensitive, far more sensitive than cyanotype. In fact the wet sensitivity brings us up to near our benchmark of the maximum sensitivity that is practical if one wants to handle the negative in a dimroom instead of a darkroom and to transfer the detector from dark bag to camera (and back again) in shaded ambient light. But after exposure we can de-sensitize the negative simply by washing and drying it, thus rendering it back to a sensitivity low enough for permanent image capture by scanning. But even more importantly, since we effectively sensitize the paper by brushing water onto it, we are back to what is essentially a hand-brushed negative. Only the parts that receive the accelerator are sensitive enough for image making in the camera.

With the right choice of paper and accelerator, EP photography can achieve a usable negative of a standard scene on a sunny day at in only 5 min. And the wavelength response of EP negatives is broader than that of cyanotype, extending well into the green region of the visible spectrum. Thus, in contrast to cyanonegative photography, ordinary camera lenses can be used, there is little need for a focus offset, and reflected light from the subject is not nearly so drowned out by the sky.

Cyanonegative photography is barely worth the bother unless it is a bright sunny day, and even then a very long exposure with a fast simple lens is required to capture more than a silhouette against the sky. EP photography, on the other hand, is still possible with a (relatively inexpensive) standard lens from an old Speed Graphic camera, even on an overcast day. Even room interiors can be captured, if illuminated by daylight through a large window.

See figure 7.12 for two examples of the kind of look that is easily achieved with EP photography. In the example on the left, the patterns in the sky resulted from wrinkles in the paper negative and air bubbles in the accelerator. And of course, as is the case with all VLS photography, the exposures are long enough that motion is spread out in time or erased. In the example on the right, taken on a windy day, the ends of the tree branches moved but the trunk was motionless during the 15 min exposure. In the two examples on the right in figure 7.13, detail has been added to the sky by the physical process itself.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.