In order to take advantage of the greater resolution available at the lower density 
and to accommodate the probable brightness range of the subject it may be necessary to 
reduce development and therefore increase exposure by amounts that will be determined 
by circumstances. 
Image motion. Image motion due to ground speed and scale can be reduced 
either by reducing the time of exposure, or by adopting some form of image motion 
compensation, involving a controlled movement of the film, or camera, or plane, during 
the time of exposure. (The last, which has been called “goldfinching”, after that bird’s 
flight pattern, may have some possibilities which should be investigated). 
Image motion due to camera vibration can be reduced either by reducing the time 
of exposure, or by improving the camera mount and so reducing camera vibration. 
The latter deserves more serious consideration than it has received from camera 
manufacturers and operators. 
Tolerable image motion. It seems obvious that perceptible image motion will 
reduce resolution, and conversely that lens-film resolution will determine the minimum 
perceptible, and therefore the maximum tolerable, image motion. Ihe question remains, 
what motion, as a fraction of the minimum resolvable distance, is perceptible and there- 
fore sufficient to reduce resolution? Brock has stated that image motion less than 0.6 
times the resolvable distance will not appreciably affect resolution, and Trott, in à 
recent paper on “The Effect of Motion on Resolution” presented at the American 
Society of Photogrammetry 1960 indicates the following relation between motion and 
resolution: 
Image Motion —Resolvable Distance % Loss in Resolution 
€ 
1.0 30% 
8 21 
0 14 
25 11 
4 7 
BS. 4 
Prior to the publication of this paper the present author had chosen, somewhat 
arbitrarily, the value of 0.3, and prepared the following table, to which are now added 
the values for 0.4, 0.5 and 0.6 and the corresponding losses in resolution. 
Tolerable Motion in microns and % loss in Resolution 
Lens-Film 
Resolution 
Resolved Distance 
in microns 
in lines/mm. 1000 300 100 | 500 600 
R R R R R R 
| 4% 7% 11% 14% 
5 | 200 60 80 | 100 120 
10 100 30 40 50 60 
15 | 67 20 27 33 | 40 
20 50 15 20 25 30 
25 40 12 16 20 | 24 
30 33 10 13 17 20 
  
Tolerable time of exposure 
(1) Considering ground speed and scale only 
The speed of the image across the film V, is equal to the scale S the speed of 
the plane V, or, in appropriate units,