Photography for Archaeology
Some Thoughts and Images on Proper Utilization of Photography of Archaeological Excavation
Some Thoughts and Images on Proper Utilization of Photography of Archaeological Excavation
Much of the photography of archaeological excavation is of highly variable quality, and is often lacking in deliberate methodology, leading to results which are of limited utility when analysis of excavation is performed later. What follows are some thoughts of methods I've developed and used.
From a point of view of technical method, choice of equipment is always important, and careful choice does, as is usually the case, improve outcomes. For the photos reproduced here, equipment was generally as follows; Canon 5D SLR (MK 1, 12.8 mp, full frame sensor), 17-40mm Canon EF-L lens, Canon 580EX flash unit, and Canon coil cord for dedicated off camera flash. There are a few simple reasons for these choices, in addition to overall quality and availability of this equipment. Full frame cameras usually have larger photosites than cameras of smaller sensor size, and this (according to some experts) provides somewhat better sensitivity to color range and a larger native color gamut, and for this application, sensitivity to minute variations in color provides advantage in being able to separate out the strata in soil profiles based on color. Larger files are also useful, as this permits zooming in on small areas of a profile shot with minimal loss of detail. Full frame sensors also permit the use of lenses of shorter focal length and wider angle of view, without using extreme wide angle lenses developed for cameras of smaller sensors, which can produce unacceptable levels of rectilinear distortion in the images. Many professional quality full-frame lenses, like the Canon L series, are not only of better quality than most of the sub-full frame lenses, but have dust seals (which will help provide a longer life to the equipment used in such conditions) , and usually have lower distortion and better flat field performance. Use of camera flash is also to be recommended, since the color temperature of the light produced is consistent, and allows easier comparison between photographs of different areas of the excavation site. A coil cord providing full flash dedication is also essential, since this permits consistent flash control, and the ability to position the flash in such a way as to select lighting angles that permit maximum control of lighting relief in order to show texture of the soil profile.
When using the camera for photographing the sidewalls or unit floors, the ideal is always to have the camera's film or sensor plane perfectly parallel and centered with respect to the plane of the area being photographed. The physical reality of archaeological excavation often makes this impractical, however, since the unit may be too narrow to allow the camera to be placed exactly opposite of the are being photographed. In most cases, this means that the sidewall must be photographed at an angle, and the photographer must select an angle which will introduce the least possible distortion into the image. Some of this distortion may be corrected using a "free" or "perspective" transform control such as is found in Photoshop, but of course it is better not to have to correct, as this inevitably introduces some dimensional distortion. Another solution is to lower the camera into the unit or trench on a monopod upside down, so that the camera can be positioned as close a possible to the ideal recording position. Using a monopod in this way is perhaps the ideal way to photograph sidewall exposures, particularly if the camera can be tethered to a laptop to control framing and firing. (I've not tried this yet, and if anyone reading this does, please let me know how it worked out.) Of course, it goes without saying that all standard procedures in unit logging apply in the case of photography. Sidewalls, features, and artifacts in situ are, like the site itself, a form of data which changes and is destroyed by the process of excavation. Photographs of the context of these things should be treated exactly like any recovered data; photos should always contain clear site, level and directional information. No exceptions. I know that everyone knows this, but I've seen more than one site photo containing a previously unnoticed feature or aspect, only to have a crew member ask "huh, that sure is interesting, where was that?"
Which brings me to the final part of this brief consideration; workflow. Photography should be integrated into the normal workflow of the excavation. Ideally, photographs should be made of every level of every unit. Excavators should be able to call on the photographer at the completion of each level. This may seem time consuming, but if integrated into the process properly, it goes smoothly, and consistency, habit and attention to detail are essential for maximum recovery of useful data, as I am sure we are all aware. In addition, as I said above, photographs should be treated like any kind of data, the results of each days photography should be logged, downloaded and recorded to a form of static media each day, as part of the photographer's normal workflow. This is particularly important because the dusty conditions of an archaeological site dramatically increase the possibility of equipment damage and/or failure. Checking your recording processes every day will greatly reduce the chance that a card, camera, or computer failure will cause the loss of irreplaceable work.
I hope this brief overview will provide some useful suggestions, and I would welcome any corrections or additions you have to offer.
JLLP
I would like to thank Bill Roop, Kathy Flynn and Sally Evans of ARS Archaeology in Petaluma, California, for asking me to help out on the project that appears in these images, for their kind permission to use the photos, and for the wonderful sense of humor and cooperation they have always shown as colleagues and friends.
From a point of view of technical method, choice of equipment is always important, and careful choice does, as is usually the case, improve outcomes. For the photos reproduced here, equipment was generally as follows; Canon 5D SLR (MK 1, 12.8 mp, full frame sensor), 17-40mm Canon EF-L lens, Canon 580EX flash unit, and Canon coil cord for dedicated off camera flash. There are a few simple reasons for these choices, in addition to overall quality and availability of this equipment. Full frame cameras usually have larger photosites than cameras of smaller sensor size, and this (according to some experts) provides somewhat better sensitivity to color range and a larger native color gamut, and for this application, sensitivity to minute variations in color provides advantage in being able to separate out the strata in soil profiles based on color. Larger files are also useful, as this permits zooming in on small areas of a profile shot with minimal loss of detail. Full frame sensors also permit the use of lenses of shorter focal length and wider angle of view, without using extreme wide angle lenses developed for cameras of smaller sensors, which can produce unacceptable levels of rectilinear distortion in the images. Many professional quality full-frame lenses, like the Canon L series, are not only of better quality than most of the sub-full frame lenses, but have dust seals (which will help provide a longer life to the equipment used in such conditions) , and usually have lower distortion and better flat field performance. Use of camera flash is also to be recommended, since the color temperature of the light produced is consistent, and allows easier comparison between photographs of different areas of the excavation site. A coil cord providing full flash dedication is also essential, since this permits consistent flash control, and the ability to position the flash in such a way as to select lighting angles that permit maximum control of lighting relief in order to show texture of the soil profile.
When using the camera for photographing the sidewalls or unit floors, the ideal is always to have the camera's film or sensor plane perfectly parallel and centered with respect to the plane of the area being photographed. The physical reality of archaeological excavation often makes this impractical, however, since the unit may be too narrow to allow the camera to be placed exactly opposite of the are being photographed. In most cases, this means that the sidewall must be photographed at an angle, and the photographer must select an angle which will introduce the least possible distortion into the image. Some of this distortion may be corrected using a "free" or "perspective" transform control such as is found in Photoshop, but of course it is better not to have to correct, as this inevitably introduces some dimensional distortion. Another solution is to lower the camera into the unit or trench on a monopod upside down, so that the camera can be positioned as close a possible to the ideal recording position. Using a monopod in this way is perhaps the ideal way to photograph sidewall exposures, particularly if the camera can be tethered to a laptop to control framing and firing. (I've not tried this yet, and if anyone reading this does, please let me know how it worked out.) Of course, it goes without saying that all standard procedures in unit logging apply in the case of photography. Sidewalls, features, and artifacts in situ are, like the site itself, a form of data which changes and is destroyed by the process of excavation. Photographs of the context of these things should be treated exactly like any recovered data; photos should always contain clear site, level and directional information. No exceptions. I know that everyone knows this, but I've seen more than one site photo containing a previously unnoticed feature or aspect, only to have a crew member ask "huh, that sure is interesting, where was that?"
Which brings me to the final part of this brief consideration; workflow. Photography should be integrated into the normal workflow of the excavation. Ideally, photographs should be made of every level of every unit. Excavators should be able to call on the photographer at the completion of each level. This may seem time consuming, but if integrated into the process properly, it goes smoothly, and consistency, habit and attention to detail are essential for maximum recovery of useful data, as I am sure we are all aware. In addition, as I said above, photographs should be treated like any kind of data, the results of each days photography should be logged, downloaded and recorded to a form of static media each day, as part of the photographer's normal workflow. This is particularly important because the dusty conditions of an archaeological site dramatically increase the possibility of equipment damage and/or failure. Checking your recording processes every day will greatly reduce the chance that a card, camera, or computer failure will cause the loss of irreplaceable work.
I hope this brief overview will provide some useful suggestions, and I would welcome any corrections or additions you have to offer.
JLLP
I would like to thank Bill Roop, Kathy Flynn and Sally Evans of ARS Archaeology in Petaluma, California, for asking me to help out on the project that appears in these images, for their kind permission to use the photos, and for the wonderful sense of humor and cooperation they have always shown as colleagues and friends.
