I'll pass this along. Thanks. Lea ----- Original Message ----- From: "ADavidhazy" <ANDPPH@ritvax.isc.rit.edu> To: "List for Photo/Imaging Educators - Professionals - Students" <photoforum@listserver.isc.rit.edu> Cc: <ANDPPH@vmsmail.rit.edu> Sent: Friday, September 06, 2002 7:44 AM Subject: Re: l..o..n..g exposure film or paper? > Lea, > > It is not quite clear what your friend wants to do but if you take plain > enlarging photo paper and place your hand on it and keep it there while the > paper is exposed to reasonably strong white light (as in making a photogram) > after about 5 minutes of such a situation if you remove your hand you will see > a perceptible difference between the paper that was covered and that which was > not ... essentially a photogram of your hand. This shadowimage will, of course, > eventually fade away. > > On the other hand, if you preexpose a piece of paper to some image then it can > only be developed under safelight conditions if you expect the image to be > visible against the fog that would be apparent if a safelight is not used or if > fogging light reaches the paper. The stage can be flooded with red light during > the process I guess. Making a darkroom out the theatre. > > Anyway, another way to deal with this is to cover the paper with red > cellophane and dream up a way of spreading developer over the paper without > letting white light leak under the cellophane to an appreciable extent. > > I am sure there are variations on the theme ... there may also be other > materials that change on exposure to light - I have seen one that is used to > demonstrate high speed photography in a science museum. It is a phosphorescent > material that reacts quickly but where the change in brightness of the material > fades away slowly - and then it can be "flashed" again. Visitors to the exhibit > jump between a flash and the screen and leave a temporary shadowgram of their > "flying" bodies impressed on the screen. > > Andy > > > A friend is looking to use either photo paper of photo film in a performance > art piece he is doing and he wants something with an exposure time of about 5 > minutes...meaning a change will take place and be seeable by th audience in > that much time. > > >
