2Q0 



THE GUIDE TO NATURE 



BEARD 

 A very beautiful and persistent flower that gi 

 Mountain deserts. 



life size picture on our 4x5 plate. We 

 now set up our instrument, and as the 

 picture is to be life size, we measure 

 so that the distance from the ground 

 glass to the middle of the mushroom 

 is just four times the focal length of 

 the lens. Thus, if the focal length is 

 six inches, which it usually is in a 4x5 



A HORNED TOAD. 



camera, then the distance from the 

 ground glass to the mushroom should 

 be twenty-four inches. Since our ob- 

 ject is small and near the ground, only 

 the upper joints of the tripod can be 



TONGUE. 



ows abundantly alcng the dry ravines in the Rocky 



used, and even then we shall probably 

 need to tip the camera a little on the 

 tilting head, to bring the image on the 

 ground glass. After the camera has 

 been set firmly, run out the front until 

 it is about midway between the ground 

 glass and the object, and focus on the 

 ground glass. The focusing must be 

 very accurately done, because all lenses 

 used at this distance from the things 

 to be photographed, have little depth 

 of focus. Focus neither on the nearer 

 nor on the farther parts, but about half- 

 way between, otherwise some part of 

 tbe finished picture will be out of focus. 

 Be careful as we may on this point. 

 some part of our image will be blurred 

 unless the whole object lies near the 

 same plane. This difficulty is over- 

 come to a great degree by the use of 

 smaller stops. Of course the length of 

 exposure is greatly increased, as well 

 as the danger of losing plates and films 

 from motion. But one must choose 

 between the loss of a few plates with 

 some clear pictures, and having all the 

 pictures fuzzy. For all my work I 

 prefer to use stop 128, giving full time, 

 and running the risk of a little waste. 

 The light should be neither behind 

 nor in front of the camera, but at the 



