8-1/2 × 17.52 = 8.5 × 100 × 17.52 = 14,892 inches = 413 yards.
Instantaneous photography can only be successfully performed in very bright and actinic light, and should never be attempted on dull days, as underexposure will be the inevitable result. In developing it is necessary to employ a strong developer to bring up the detail. Some operators make use of an accelerator for this purpose, but it is not to be recommended; the simplest is a few drops of hyposulphite solution added to about 10 ounces of water. In this the plate is bathed for a few seconds previous to development.
The following is a table by H. E. Tolman showing displacement on ground glass of objects in motion:
| Miles per Hour. | Feet per Second. | Distance on Ground Glass in Inches with Object 30 Feet Away. | Same with Object 60 Feet Away. | Same with Object 120 Feet Away. |
| 1 | 1-1/2 | .29 | .15 | .073 |
| 2 | 3 | .59 | .29 | .147 |
| 3 | 4-1/2 | .88 | .44 | .220 |
| 4 | 6 | 1.17 | .59 | .293 |
| 5 | 7-1/2 | 1.47 | .73 | .367 |
| 6 | 9 | 1.76 | .88 | .440 |
| 7 | 10-1/2 | 2.05 | 1.03 | .513 |
| 8 | 12 | 2.35 | 1.17 | .587 |
| 9 | 13 | 2.64 | 1.32 | .660 |
| 10 | 14-1/2 | 2.93 | 1.47 | .733 |
| 11 | 16 | 3.23 | 1.61 | .807 |
| 12 | 17-1/2 | 3.52 | 1.76 | .880 |
| 13 | 19 | 3.81 | 1.91 | .953 |
| 14 | 20-1/2 | 4.11 | 2.05 | 1.027 |
| 15 | 22 | 4.40 | 2.20 | 1.100 |
| 20 | 29 | 5.87 | 2.93 | 1.467 |
| 25 | 37 | 7.33 | 3.67 | 1.833 |
| 30 | 44 | 8.80 | 4.40 | 2.200 |
| 35 | 51 | 10.27 | 5.13 | 2.567 |
| 40 | 59 | 11.73 | 5.97 | 2.933 |
| 45 | 66 | 13.20 | 6.60 | 3.300 |
| 50 | 73 | 14.67 | 7.33 | 3.667 |
| 55 | 80 | 16.13 | 8.06 | 4.033 |
| 60 | 88 | 17.60 | 8.80 | 4.400 |
| 75 | 110 | 22.00 | 11.00 | 5.500 |
| 100 | 117 | 29.33 | 14.67 | 7.333 |
| 125 | 183 | 36.67 | 18.33 | 9.167 |
| 150 | 220 | 44.00 | 22.00 | 11.000 |
FIG. 82.—ARTIFICIAL REPRODUCTION AND PHOTOGRAPHING OF A MIRAGE