364 



THE (IUIDE TO NATURE 



Long Focus and Short Focus: Theo- 

 retical vs. Practical. 



Photographic instruction books tell 

 the beginner and all who read them, 

 "The shorter the focus the greater the 

 depth of focus." That may be correct 

 in theory. How about it in phases of 

 practice? Let us see. 



According to the experience of com- 

 mercial photographers and of most 

 naturalists, the unqualified assertion is 

 not wholly true, because actual prac- 

 tice proves that it is partly erroneous. 

 In actual practice I go to the fields with 

 my camera and a lens having a com- 

 bined focal length of seven and one- 

 half inches, the front section being six- 

 teen and one-half inches and the back 

 combination eleven and three-six- 

 teenths. I discover a shrub beautifully 

 in bloom. I want to fill the plate with 

 it, and yet I do not want the front nor 

 the back to be out of focus, nor do I want 

 the picture to suggest motion as it may 

 do if the wind is blowing. I make a 

 time exposure. I set the camera near 

 enough to the shrub to fill the plate 

 and I get depth by stopping down the 

 lens, but I then have everything out of 

 perspective. The branches near by are 

 too big, and the distant ones are too 

 little. With me is a friend who is just 

 beginning to use the camera. I say to 

 him, "Take off the back combination 

 and use the sixteen and one-half front 

 lens. Then by going back far enough 

 you can fill the plate and have good 

 depth. But he makes a significant ges- 

 ture, and tells me that his instruction 

 books says that long focus will not give 

 him depth of focus. And I say, "Do 

 what you please, and take what fol- 

 lows. You are not spoiling my plates." 



We tramp onward and find a bird's 

 nest on the ground. We tilt the camera 

 to get the correct focus on the nest, 

 but both the foreground and the back- 

 ground are out of focus. "How can I 

 remedy it?" he inquires. "I must stop 

 down to get all this in focus ;" while 

 I remark, "You can do that, but I like 

 better to use the back combination of 

 the lens, longer focus, get back a little 

 farther and obtain greater depth." 

 Again he murmurs something about 

 his instruction book, but I pay no heed 



to him. I do not intend to have any 

 factor enter into the discussion except 

 that of actual experience. 



On our return we pass an apple tree 

 in full bloom, and are delighted by the 

 owner's permission to take home a big 

 branch for photographic purposes. We 

 carry it indoors where there is a good 

 skylight with no air currents. Here 

 we can use a short focus by stopping 

 down the lens to get depth. But on the 

 ground glass the blossoms on the near 

 side of the bough are at least twice the 

 size of those on the far side, and thai 

 would make a misleading photographic 

 record of an interesting natural speci- 

 men. Then we take a long focus lens 

 — as long as we can get, and, to obtain 

 REAL depth, depth that shall not be a 

 distortion nor a mispresentation, we 

 retire as far as possible from the speci- 

 men, and make the exposure. It shows 

 the blossoms on both sides in almost 

 the correct proportion. But the books 

 tell us that long focus will not give 

 depth. Yet experience says that the 

 books are wrong, in making an unquali- 

 fied assertion without explaining the 

 more distant point of view of the longer 

 focus. 



I remember how years ago I was as- 

 tonished when I went into an artist's 

 studio and he told me that he had a 

 lens of some eighteen or twenty inches 

 focus. I asked what use he had for 

 such a lens. He said, "With it I can 

 fill the plate without distortion and 

 with good depth in taking a portrait." 

 "Do you mean to say," I asked, "that 

 if you want to get depth from the tip 

 of the nose to the back of the head you 

 use a long focus? I thought, and the 

 books tell me, that I must use a short 

 focus for depth." 



Is there any photographer in exis- 

 tence who, when he desires to use his 

 lens wide open or nearly so, would 

 take a short focus to get depth in pho- 

 tographing a deep subject? If there is, 

 let us know how he does it, and if there 

 is not, let us understand why our books 

 persist in stating what is the antipode 

 of all experience. 



Some one may say, "Your longer 

 focus gets greater depth because you 

 put the camera farther away and have 



