Sources for light filters:
1. Theater Service and Supply Corporation, 1792 Union Avenue, Baltimore, MD
21211, (301) 467-1225. Request roscolene acetate gelatin filters. Order
medium green #874, medium red #823, dark urban blue #866. Was about $3.35 for
20X24" sheet. I checked the percent transmittance on the Theater Service
filters from 400-700 nm (I don't know if there is transmittance below or above
this range and my spectrophotometer is average).
2. Kodak Wratten Gelatin Filters, can be purchased from VWR. I have not
used these, but they are probably the best. The percent transmittance is from
Kodak ("Kodak Photographic Filters Handbook" from Saunders for $14.95 plus
postage - phone: 716 328-7800). The Kodak filters are expensive. From VWR, the
red and green are about $50 each for a 6" sheet and the blue is about $125 for
a 6" sheet). The red is Kodak #25 (VWR 170 6811), green #58 (VWR 170 6852),
and blue #47B (VWR 170 7058).
Percent transmittance
Theater Service Kodak
red green blue red green blue
400nm 2 2 13 - - 16
425 2 2 30 - - 47
450 2 2 41 - - 36
475 2 9 28 - 1 9
500 2 24 11 - 18 1
525 2 36 3 - 53 -
550 2 22 2 - 38 -
575 3 9 2 - 12 -
600 6 5 2 72 2 -
625 19 4 2 87 - -
650 40 2 2 89 - -
675 67 2 2 89 - -
700 79 2 2 90 - -
John Browning
Plant Biology Department
University of Maryland College Park
jb189 at umdd.umd.edu
