focus. This shift in focus may be reduced by stopping down  the  lens;  however,  this  is  not  always  possible because  you  may  need  fast  shutter  speeds.  The  best method of shooting photographs through a window is to take the picture with the optical axis of the lens perpendicular to the surface of the window. The lens should be as close as possible to the surface of the window  without  touching  it.  Although  this  method allows you to take only one or two photos during each pass of the target, the quality and definition of the image is better. When shooting photographs with an SLR camera through a window or canopy, you will find it helpful to make a foam rubber "doughnut" about 2 or 3 inches thick. This foam rubber shield should be taped to the camera using surgical tape because it sticks well and can be removed without leaving a gummy residue. After attaching the foam rubber shield to the camera, you should place it against the aircraft window to block internal reflections from that part of the window that the camera "sees." The shield also absorbs vibrations from the  window. Most of your hand-held aerial work, both oblique and vertical, consists of single shots; however, you may have to fly oblique and vertical strips that require overlapping    photographs.    The    camera-to-scene distance must remain constant while you are shooting the strip. Changes in distance cause the image size to change and make matching the adjacent exposures impossible.  You  should  make  the  exposures  at regularly spaced intervals. You can determine the time interval visually between the exposures for a strip. Before the flight, mark your viewfinder to show the distance an object must move in the viewfinder to move the image 40 percent of the width of the film. During the flight, make the first exposure, hold steady, and make the second exposure after some point in the scene has moved the distance marked on the viewfinder. The marks are the same for any aircraft speed or altitude. When you are not using an SLR camera, change the marks on the viewfinder if you change either the film format or the focal length of the lens. Hand-held  vertical  photography  is  easiest  from helicopters.  You  can  lean  out  from  your  sitting  position on the floor or from a passenger seat and hold the camera  with  the  proper  attitude  for  taking  verticals. You should hold the camera firmly in your hands, keeping your torso relaxed so your arms will act as vibration dampers. Using this method, you can take vertical aerials that are incredibly sharp because of the maneuverability  of  the  helicopter,  its  capability  for  slow flight, and the possibility for both the pilot and the photographer  to  see  the  target.  Because  of  these features,  accurate  vertical  photography  is  easier  from helicopters than from fixed-wing aircraft. Most air-to-air photography you shoot will be of other aircraft. The purpose is to produce display and public affairs (PAO) photographs. You may also be assigned  to  take  air-to-air  photography  for  research  and testing   purposes.   When   shooting   air-to-air photographs,   you   should   maintain   voice communication with both the pilot flying your aircraft as   well   as   the   pilot(s)   of   the   aircraft   you   are photographing. This provides an opportunity for you to direct all the aircraft involved into position for photographs. Generally speaking, the best air-to-air photographs are made from slightly above, to the side, and slightly forward of the plane being photographed; however, you should try other views, such as from below or slightly aft  of  the  subject  aircraft.  A  longer  than  normal focal-length  lens  (80mm  or  greater  for  a  35mm  camera) should be used when you are photographing only one or two aircraft at a time. Longer focal-length lenses prevent distortion that results from using a normal or short lens. With a normal or short lens, the wings that stick out from the fuselage of the target plane and the long  nose  or  tail  section  appear  distorted  when  you photograph  them  from  close  range.  When  shooting formations of three or more aircraft, you should use a normal focal-length lens because you are farther from the subjects and distortion is not a problem. For a head-on view use a long focal-length lens and have the pilot fly the aircraft you are in across and above or below the   projected   flight   path   of   the   plane   being photographed. Of course, each of the pilots need plenty of room to avoid a mid-air collision. A better and safer way to get a head-on shot is to fly in front of the plane being photographed, in the same direction, and at the same speed. You can take this shot from the open ramp of an aircraft, such as a C-130 or CH-53. In aircraft such as these, you can stand at the edge of the open ramp; ensure that you are secured properly with a safety harness. The aircraft you are photographing does not always have to fly straight and level. Good, interesting pictures can be taken while aircraft are maneuvering, such as in a long, slow turn or in a bank. When the underside of the fuselage must be shown, request the pilot of the target aircraft to roll the plane, so the sun shines on the underside  of  the  aircraft.  For  this  shot,  the  plane containing the photographer should fly in a bank above the subject plane. This maneuver provides you with a 4-32