| Revision: | 1.1 |
| Committed: | Sat Mar 15 17:32:55 2003 UTC (22 years, 1 month ago) by greg |
| Branch: | MAIN |
| CVS Tags: | rad5R4, rad5R2, rad4R2P2, rad5R0, rad5R1, rad3R7P2, rad3R7P1, rad4R2, rad4R1, rad4R0, rad3R5, rad3R6, rad3R6P1, rad3R8, rad3R9, rad4R2P1, rad5R3, HEAD |
| Log Message: | Added and updated documentation for 3.5 release |
| # | Content |
|---|---|
| 1 | Francis found the appropriate equation for film exposure in the IES |
| 2 | handbook. There isn't an exact relation, but the following formula |
| 3 | can be used to get an approximate answer for 35mm photography: |
| 4 | |
| 5 | Radiance EXPOSURE = K * T * S / f^2 |
| 6 | |
| 7 | where: |
| 8 | T = exposure time (in seconds) |
| 9 | S = film speed (ISO ASA) |
| 10 | f = f-stop |
| 11 | K = 2.81 (conversion factor 179*PI/200) |
| 12 | |
| 13 | This came from the IES Lighting Handbook, 1987 Application Volume, section 11, |
| 14 | page 24. |
| 15 | |
| 16 | So, if you were trying to produce an image as it would appear shot at |
| 17 | 1/60 sec. on ISO ASA 100 (DIN 21) film at f-4, you would apply pfilt |
| 18 | thusly: |
| 19 | |
| 20 | pfilt -1 -e `ev "2.81*1/60*100/4^2"` raw.pic > fin.pic |