Nipher — Positive Photography: Eclipse Work. 211 



down until the liquid covers the plate, but the light should 

 then be turned on at once. When lamp-light is used this 

 precaution is not very important. In fact the writer 

 is inclined to say that such precaution is not then necessary. 

 If the exposure has been too small, either from insufficient 

 light on the object, or from insufficient time, such an exposure 

 in the light-room is a decided advantage. It carries 

 the plate farther from the zero condition, and materially 

 improves the picture. The same result may be secured by 

 turning the camera upon the sky after the usual exposure to 

 the object has been made, and before the shutter has been 

 closed. This sky- exposure may be for half a minute with a 

 No. 8 stop, but should not exceed this. The following ex- 

 periment seems to indicate that this sky exposure should be 

 after rather than before the exposure to the object. 



A white paper was pasted on a somewhat larger card of 

 dead black. It was placed against a brick wall in 

 sunlight, and with a cloudless s-ky. After a minute 

 of exposure to the plate in the camera, the black card 

 was quickly shifted laterally by a distance slightly 

 greater than its width. This was repeated ten times in an 

 exposure of ten minutes. On developing, the first of the ten 

 exposures was somewhat more distinct than those which fol- 

 lowed, but between the others no difference could be detected. 

 The last minute of the ten was as effective as the second. 

 But when the experiment is terminated at the end of the first 

 minute, the image is very indistinct. It is evident that the 

 subsequent exposure during the nine minutes served to make 

 more distinct the image of the card made during the first 

 minute. And since the plate seems to be somewhat more 

 sensitive at first than it is later in the exposure, it is better to 

 utilize this part of the exposure in securing details of the ob- 

 ject, rather than in fogging the plate beyond the zero condi- 

 tion. This difference of sensitiveness is not very marked. It 

 is difficult to see any difference in the first three and the last 

 three minutes of a six-minute exposure. This may be shown 

 in an interesting way by the following experiment. The ex- 

 perimenter should preferably be dressed in light-colored cloth- 

 ing, and should train the camera on a grass-covered hill, 



