Re: Reuse of Pyrogallol developer
Posted: Tue Jan 18, 2022 11:16 am
Here's where the use of using a rehalogenating bleach to de-fog plates got started (1988): http://edweslystudio.com/Publications/recycle.pdf
A place to discuss holography
https://www.holographyforum.org/forum/
You're confusing your units, Jody. Energy is not measured in microwatts per cm², irradiance is. Consider another form of energy, such as heat (not temperature, which is a measure of heat). If there is a certain amount of heat energy in some volume, such as a room, then the amount of heat energy is measured in Joules, or Ergs or BTU (British Thermal Units). If the heat leaks outside the room, then the amount of heat that leaves in 1 second is the power exerted by the heat, and power is measured in watts, or ergs per second or horsepower (BTU per second). However, the amount of heat leaking from the room may not be as useful as the heat leaving the room per second per unit area, so we have watts per m², or ergs per second per cm², or horsepower per feet². This is known as irradiance, or energy per unit time per unit area.jrburns47 wrote: ↑Sun Jan 23, 2022 12:44 am Dumb question, to which I believe I’ve known the answer for decades, but one needing an answer please.
If I’m reading 25mw CW at the recording plate surface, with a Newport wand detector 818-ST with no attenuator, with a normally reliable Newport 840-C light meter, and I make a one second exposure, how much energy is exposing the material in microwatts per cm2 per second? If you prefer to answer in uJ/cm2, (which I believe is the same amount of energy but in a single pulse), no problem.
How many ergs/cm2/sec?
Thanks.
My feeling is that the detector has to be perpendicular to the incoming light, because that's the direction of the actinic radiation. That is, you're measuring the value of the energy imparted to the medium in that particular direction, ie the value of the poynting vector. If you measure parallel to the plate, you're measuring the value of the cos of the Poynting vector and so giving the plate less energy than it requires.
Not true. The beam ratio is determined by the actual actinic radiation actually entering the plate. Therefore, Fresnel reflection need to be considered, since such reflection diminish the actual radiation entering the plate. So, for example, if you were recording at angles of 0 and 80 degrees, then very little of the beam power measured at 80 degrees is actually entering the plate. The meter reading itself is independent of polarisation and therefore cannot determine how much power is entering the plate.