PHOTOGRAPHIC ENERGIES OF DIFFERENT RAYS
The following experiments are preliminary only, and were undertaken to determine the relationship of the several colours of the tintometrical scales, to their associated photographic values, under different conditions of light and times of exposure, the end in view being the hope of standardizing screens, papers and impressions.
The standardized colours act as selective light absorbents on the same principle as screens for trichromatic colour work, but differ from these in their having a definite standard of colour depth and colour purity.
Work of this character requires paper of a known degree of sensitiveness, but on inquiry it was found that no reliable standard had as yet been established. On this, six makes of “white” paper were purchased in the open market and submitted to exposures under the following conditions:—
Six slips of the sensitized papers were covered by a thin metal plate, pierced by six rows of apertures, a complete row lying over each sample of paper. The rows contained seven apertures each, one being left uncovered to receive the full energy of the impinging light. The remaining six were covered respectively by a Red, Orange, Yellow, Green, Blue or Violet standardized screen of 15 units colour intensity; the whole was fitted into a suitable exposure frame. Many exposures were made, from which the four following were selected:—
No. 1. 20 min. exposure to a dull sky.
No. 2. 10 min. exposure to bright sunlight.
No. 3. 20 min. exposure to bright sunlight.
No. 4. 30 min. exposure to bright sunlight.
The results are arranged in Tables VI and VII.
Table VII contains results of different exposures under sunlight conditions.
TABLE VI.
DULL SOUTH LIGHT.
20 Minutes’ Exposure on White Sensitized Papers.
| Papers | Open Screen. | Red Screen. | Orange Screen. | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Blk. | Or. | Red. | Blk. | Or. | Yel. | Blk. | Or. | Red. | |
| 1 | 7·8 | 4·2 | 6·0 | 2·0 | 4·8 | 3·0 | — | ·3 | ·2 |
| Red. | |||||||||
| 2 | 6·0 | 5·0 | 5·5 | 1·9 | 3·1 | ·4 | — | — | — |
| Yel. | |||||||||
| 3 | 7·8 | 3·2 | 7·0 | 2·7 | 4·7 | 3·0 | — | — | — |
| Red. | |||||||||
| 4 | 7·2 | 4·3 | 6·0 | 2·2 | 3·2 | ·2 | — | — | — |
| 5 | 5·8 | 7·2 | 4·0 | 1·9 | 2·3 | ·8 | — | — | — |
| 6 | 5·6 | 7·4 | 4·0 | 1·8 | 2·6 | 6 | — | — | — |
| Papers | Yellow Screen. | Green Screen. | Blue Screen. | Violet Screen. | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Blk. | Or. | Red. | Blk. | Or. | Red. | Blk. | Or. | Red. | Blk. | Or. | Red. | |
| 1 | 2·0 | 3·0 | 1·6 | — | — | — | 3·9 | 7·6 | 3·5 | ·2 | ·4 | 1·0 |
| Yel. | ||||||||||||
| 2 | ·4 | ·4 | 1·0 | — | — | — | 4·3 | 9·2 | 4·5 | ·2 | ·8 | ·8 |
| Red. | ||||||||||||
| 3 | 1·2 | ·5 | ·8 | — | — | — | 3·7 | 9·3 | 2·0 | ·7 | ·6 | ·9 |
| Yel. | ||||||||||||
| 4 | 1·2 | ·1 | 1·2 | — | — | — | 3·4 | 1·1 | 1·0 | ·7 | ·7 | ·9 |
| 5 | 1·0 | ·3 | ·3 | — | — | — | 3·3 | 8·7 | 2·0 | ·3 | ·3 | 1·2 |
| Red. | ||||||||||||
| 6 | ·2 | ·3 | ·4 | — | — | — | 3·6 | 8·9 | 1·5 | ·4 | ·2 | ·9 |
TABLE VII.
BRIGHT SUNLIGHT (South), 18—9—12.
10 Minutes’ Exposure on White Sensitized Papers.
| No. | Open Screen. | Red Screen. | Orange Screen. | Yellow Screen. | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Blk. | Or. | Red. | Blk. | Or. | Yel. | Blk. | Or. | Red. | Blk. | Or. | Red. | ||
| 1 | 8·4 | 1·6 | 6·5 | 2·8 | 6·8 | 1·9 | ·34 | 1·41 | ·55 | 2·3 | 7·1 | — | |
| 2 | 8·2 | 2·0 | 6·3 | 2·7 | 4·7 | 3·6 | — | — | — | ·8 | 1·9 | ·70 | |
| 3 | 7·8 | 2·2 | 7·5 | 2·4 | 7·0 | 4·1 | — | — | — | 2·4 | 4·2 | ·80 | |
| 4 | 7·8 | 1·6 | 8·6 | 2·4 | 5·4 | 3·2 | — | — | — | 1·5 | 2·3 | ·70 | |
| 5 | 6·4 | 4·4 | 7·7 | 2·4 | 5·2 | 3·0 | — | — | — | ·9 | 1·8 | ·80 | |
| 6 | 5·2 | 6·3 | 5·5 | 2·3 | 5·1 | 3·0 | — | — | — | 1·1 | 2·0 | ·80 | |
BRIGHT SUNLIGHT (South), 18—9—12. 20 Minutes. | |||||||||||||
| Vio. | Red. | Or. | Red. | Or. | Yel. | Red. | |||||||
| 1 | 10·6 | 1·4 | 5·0 | 7·0 | 2·2 | 8·3 | 1·1 | 3·6 | ·9 | 10·0 | — | 7·0 | |
| Red. | Or. | ||||||||||||
| 2 | 10·0 | — | ·8 | 7·0 | 2·6 | 7·4 | — | 1·0 | ·3 | 7·4 | 2·0 | 3·6 | |
| Or. | |||||||||||||
| 3 | 9·2 | 1·6 | 2·2 | 4·5 | 5·5 | 8·0 | 1·8 | 7·4 | — | 5·2 | 4·2 | 8·1 | |
| Or. | |||||||||||||
| 4 | 10·6 | ·4 | 3·5 | 6·0 | 4·2 | 8·3 | ·44 | 1·36 | ·8 | 9·0 | 2·5 | 5·0 | |
| 5 | 10·0 | ·8 | 5·7 | 6·2 | 4·0 | 8·3 | — | ·7 | ·45 | 7·0 | 5·0 | 4·0 | |
| 6 | 6·2 | 4·6 | 7·7 | 5·0 | 7·5 | 4·0 | ·2 | ·4 | ·5 | 5·4 | 7·1 | 4·5 | |
BRIGHT SUNLIGHT (South), 18—9—12. 30 Minutes. | |||||||||||||
| Or. | Red. | Or. | Red. | Or. | Red. | Or. | Red. | ||||||
| 1 | 10·6 | ·9 | 1·5 | 6·4 | 4·4 | 5·7 | 2·6 | 7·8 | 1·1 | 5·2 | 3·4 | 10·4 | |
| 2 | 9·2 | 1·4 | 2·9 | 6·2 | 5·3 | 5·5 | ·1 | ·7 | ·4 | 7·8 | 3·0 | 5·2 | |
| 3 | 10·8 | 1·2 | 1·5 | 7·2 | 3·4 | 8·4 | ·7 | 2·0 | ·2 | 9·2 | 1·6 | 5·2 | |
| 4 | 10·0 | 2·0 | 1·5 | 6·2 | 4·4 | 6·9 | ·5 | 1·0 | ·7 | 8·2 | 2·0 | 7·3 | |
| 5 | 9·6 | 4·4 | 4·5 | 5·8 | 5·0 | 7·2 | ·2 | 1·9 | ·7 | 6·2 | 3·8 | 6·5 | |
| 6 | 6·6 | 7·9 | 5·0 | 4·8 | 7·2 | 5·0 | ·2 | ·5 | ·55 | 5·0 | 7·5 | 2·0 | |
TABLE VII.
BRIGHT SUNLIGHT (South), 18—9—12.
10 Minutes’ Exposure on White Sensitized Papers.
| No. | Green Screen. | Blue Screen. | Violet Screen. | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Blk. | Or. | Red. | Blk. | Or. | Red. | Blk. | Or. | Yel. | |
| 1 | ·26 | ·69 | ·10 | 5·2 | 4·4 | 8·4 | 1·75 | 3·65 | ·40 |
| 2 | — | ·15 | ·03 | 6·0 | 3·8 | 6·7 | 1·7 | 3·9 | ·40 |
| 3 | ·22 | ·02 | ·04 | 5·6 | 5·9 | 6·5 | 1·5 | 3·5 | 1·2 |
| 4 | ·19 | ·05 | ·12 | 4·8 | 5·6 | 6·6 | 1·3 | 3·2 | — |
| Red. | |||||||||
| 5 | — | — | — | 4·0 | 10·5 | 2·0 | ·6 | 1·7 | 1·0 |
| 6 | — | — | — | 4·0 | 11·5 | 1·0 | ·5 | 1·9 | 1·1 |
BRIGHT SUNLIGHT (South), 18—9—12. 20 Minutes. | |||||||||
| Or. | Yel. | Or. | Red. | Or. | Red. | ||||
| 1 | 3·1 | 6·1 | 1·8 | 8·0 | 2·0 | 8·5 | 4·5 | 7·5 | 4·5 |
| Or. | |||||||||
| 2 | 1·9 | 3·7 | ·8 | 8·8 | ·6 | 3·6 | 5·0 | 6·5 | 4·5 |
| 3 | 1·0 | 7·0 | 1·6 | 8·6 | 1·4 | 3·5 | 4·0 | 8·5 | 4·5 |
| 4 | 1·8 | 4·8 | 1·2 | 8·0 | 2·2 | 6·8 | 4·5 | 7·5 | 4·5 |
| 5 | 1·7 | 4·9 | 1·4 | 7·6 | 2·4 | 8·0 | 4·0 | 8·5 | 4·0 |
| Red | |||||||||
| 6 | 1·8 | 3·4 | ·4 | 6·4 | 4·4 | 8·2 | 3·5 | 8·5 | 1·0 |
BRIGHT SUNLIGHT (South), 18—9—12. 30 Minutes. | |||||||||
| Or. | Yel. | Or. | Red. | Or. | Red. | ||||
| 1 | 1·0 | 6·8 | ·2 | 6·4 | 2·6 | 7·5 | 4·2 | 6·8 | 6·0 |
| 2 | 1·8 | 3·4 | ·2 | 8·4 | 8 | 3·8 | 5·4 | 8·1 | 1·0 |
| 3 | 2·2 | 5·2 | 2·2 | 8·0 | 2·0 | 7·5 | 4·5 | 8·5 | 4·0 |
| 4 | 2·5 | 4·7 | 2·0 | 8·0 | 1·6 | 7·4 | 3·7 | 10·3 | 1·0 |
| Yel. | |||||||||
| 5 | 1·6 | 4·2 | 2·8 | 7·6 | 2·6 | 6·8 | 3·1 | 9·4 | 1·5 |
| 6 | 1·5 | 3·9 | ·2 | 6·4 | 7·6 | 5·5 | 3·4 | 9·7 | 1·5 |
It would be unsafe to draw definite conclusions from a few experiments, but so far as permissible, the results show considerable differences, both in depth and in colour, of the energy of the different rays, for instance—
Compare Nos. 1 and 6 under 20 min. sunlight.
| Black. | Orange. | Red. | |||
| No. 1 | 10·6 | + | 1·4 | + | 5·0 |
| No. 6 | 6·2 | + | 4·6 | + | 7·7 |
or again 3 and 6, the maximum and minimum, under 30 min. exposure.
| Black. | Orange. | Red. | |||
| No. 3 | 10·8 | + | 1·2 | + | 1·5 |
| No. 6 | 6·6 | + | 7·9 | + | 5·0 |
The sensitiveness of Nos. 2, 4 and 5 appears to have been exhausted by 20 min. exposure to sunlight, further exposure showing no reaction; whilst the sensitiveness of Nos. 1, 3 and 6 do not appear to have been exhausted by 30 min. sunlight exposure.
Other noticeable points are the small action under the Orange, Green and Violet screens, and the greater, although variable proportion of colour to black under all the colour screens.