APPENDIX E 



WESTON FILM -SPEED RATINGS 



The film-speed ratings given in this appendix are those compiled by the Weston Electrical Instru- 

 ment Co. In conjunction with suitably calibrated exposure meters these ratings may be used to deter- 

 mine correct exposure. However, it should be recognized that processing conditions and errors in 

 shutter speed or aperture may make it necessary to deviate from these speed ratings in order to obtain 

 the best negatives. T indicates tentative value subject to further test. 



Film Listing 



The number given for each film in the listing on this sheet represents a group of three consecutive 

 emulsion speeds. For the sake of simplicity, the group number listed is the mean value for the group, 

 and is the rating to use for those who have had no previous experience with the film or who do not know 

 what developer will be used. 



The following table shows the group number and the three emulsion speeds that it represents. 



Speed Range 



160—200 — 250 



80 — 100 — 125 



40— 50— 64 



20 — 24— 32 



10 — 12— 16 



5 — 6 — 8 



2.5 — 3— 4 



1.2—1.5— 2 



Daylight 



Group Number 



200 



100 



50 



24 



12 



6 



3 



1.5 



Tungsten 



Speed Range 



100 — 125—160 



50— 64— 80 



24— 32— 40 



12— 16— 20 



6— 8— 10 



3— 4— 5 



1 . 5— 2—2 . 5 



Group Number 



125 



64 



32 



16 



8 



4 



Rolls and Packs 



Daylight Tungsten 



Group Group 



No. No. 



Agfa 



100 Superpan Press 64 



50T Super Plenachrome 32T 



24 Finopan 16 



24 Plenachrome 16 



12 Standard 4 



24 Superpan 16 



Eastman 



100 Super XX 64 



24 Verichrome 16 



24 Panatomic X 16 



12 N. C 4 



Gevaert 



24 Panchromosa 16 



12 Express Superchrome 4 



850 



