advance mechanism with little film wastage. A special accessory was available that used the otherwise blank frame near the start of the roll to identify the roll, though the procedure for using it was rather elaborate. Because camera lenses invert the image and flip it left to right, orienting the film strip so that the image's "up" is up, and its "left" is to the left, the left-eye image of the stereo pair is to the viewer's right (see the included photograph). Note that in the Realist 45 the film cartridge is loaded on the right side of the camera, causing the images to be upside-down relative to the numbers. The standard Realist and Kodak Stereo Camera have the cartridge on the left side, so the images have the same orientation as the numbers. The routine for taking a photograph with a Stereo Realist is elaborate, compared to a modern camera. One must lift the lens cover, focus, manually set the aperture and shutter speed, cock the shutter and then take the picture. The wind release button must be depressed briefly while beginning to wind the film to the next frame. The film winding is then completed so that the camera is ready to shoot another pair of images. Later-model cameras featured a double exposure button, which could be pulled out to make a double exposure but could otherwise be left alone, as well as a depth-of-field scale on the focusing knob. Many also had red marks on f/6.3, 1/50 and on 20 feet. This was called "The Three R's in Outdoor Stereo Photography" and is based on the then-standard ASA 10 color slide film. Earlier cameras lacked these features but they could be added. The double exposure button would have to be installed by the factory, but the depth-of-field scale and red marks could be added by a dealer or even the camera's owner. Thus, older model Realists are sometimes found with red marks or depth-of-field scales, but without double exposure buttons. A characteristic of "Stereo Realist" type cameras is that the lenses are at a fixed separation, known as "fixed stereo base", which was slightly more than the average distance between the human eyes. The stereo base was ideal for subjects that were 7 to 20 feet from the camera, which worked well for most pictures but was somewhat lacking for more distant scenic shots. Accessories were available