allen positions a model in front of his camera and faces it to the sun. the whole setup has to be calculated very, very carefully before you can start the exposure. a medieval artist would need to ensure that any image projected on a sheet could be permanently fixed. the sheet would be soaked with photographic chemicals. today, this means using silver salts. both silver nitrate and silver sulfate have been around in europe since the 13th century. it s very easy to make. a sheet is soaked in silver sulfate solution. dried. and then mounted in the camera.
calculated very, very carefully before you can start the exposure. a medieval artist would need to ensure that any image projected on a sheet could be permanently fixed. the sheet would be soaked with photographic chemicals. today, this means using silver salts. both silver nitrate and silver sulfate have been around in europe since the 13th century. it s very easy to make. a sheet is soaked in silver sulfate solution. dried. and then mounted in the camera. after eight hours exposure,
the whole setup has to be calculated very, very carefully before you can start the exposure. a medieval artist would need to ensure that any image projected on a sheet could be permanently fixed. the sheet would be soaked with photographic chemicals. today, this means using silver salts. both silver nitrate and silver sulfate have been around in europe since the 13th century. it s very easy to make. a sheet is soaked in silver sulfate solution. dried. and then mounted in the camera.
allow barge traffic to go through was properly in place last night. we re not sure what happened here whether that boat was speeding or whether it just took a wrong turn and ran into a barge that was passing. four people were injured. two people have been missing. we believe the sheriff has confirmed the body of the dried to be who was scheduled to get married two weeks from today has been found. they are searching waters for any signs of the best man of this wedding party. we ll give you more information as we get it here. we go to with washington and the obama administration stepping up efforts to apprehend edward snowden. he s been living in the transit area of the moscow airport for the past month. let s get details from kristen welker. what is the obama administration doing about this? reporter: good afternoon. the obama administration has been pressuring russian officials to send snowden back to the united states publicly and private lyprivately.
that finally devotes the resources we need in the fight against extremism in afghanistan and pakistan. we ve reset relations with russia and signed a historic new s.t.a.r.t. treaty. after years adried, we brought together a broad collision to hold iran accountable and applied pressure through tough new sanctions. we have renewed the push for peace in the middle east, charted a course to security vulnerable nuclear materials within four years and reestablished our leadership within the pacific rim and forging a response at the global level to the economic crisis. in between, we ve responded to a range of crises like haiti and the floods now in pakistan that are required from us as leaders in the world. in short we have spared no effort to keep the american people safe while repairing old alliances, building new partnerships, and restoring