Editing Exposing Screens (section)

=== Other notes on exposure ===

According to the article below with a point light, the height of the lamp should be the diagonal length of the screen.  

If a correct exposure time is known, and the lamp needs to be adjusted, the new exposure time can be calculated using the '''inverse-square law''' <ref name="inverse-square">[http://photography.tutsplus.com/articles/rules-for-perfect-lighting-understanding-the-inverse-square-law--photo-3483 Inverse-Square Law and Lighting], tuts+</ref>. 

The power of the light is equal to the inverse square of its distance from the subject.

E.g. if a light is 1 meter away from the subject, moving it 2 meters away will decrease its power by 1/4. (1 divided by 2 meters * 2 meters)

To determine the new exposure time, `(new height/original height)<sup>2</sup> * original exposure time`.

==== Trial & error ====

Ok so with a yellow screen & 550W/17"/9 Min it seemed hard to get the emulsion out. I had to make 3-4 passes. At 8-&frac12; minutes, the emulsion came out pretty quickly with no issues with the exposed emulsion. 

Then I exposed a screen with white mesh at 18-&frac12; minutes and the exposed emulsion washed out. 

The signindustry.com site says that yellow mesh should take ''longer'' to expose. I don't know if the mesh color is contributing to this behavior at this point.

* [http://www.signindustry.com/screen/articles/2003-11-26-BS-ExposingDirectEmulons3.php3 Exposing Direct Emulsions] (signindustry.com)<br />''Hints at formulas for determining lamp height and exposure time.''