With the advent of high-gain image intensification and high-speed cine-fluorography, better and more informative cinefluorograms are obtained and more precise motion analysis is possible. Often the radiologist wishes a time-event were available to refer back to in a specific frame. This has been investigated and achieved in the past by several means, mainly split-mirror photography (1–3), and through film-base posterior approach (4). The first method implies a reduction in the amount of light reaching the camera from the output phosphor of the image intensifier (which has to be compensated by increasing the x-ray output), and the second requires an additional shutter-mechanism and specific modifications of the camera to be used. Since the shape of the image-intensifier output phosphor is circular and the motion picture frame rectangular, it is obvious and well known that the camera “sees” four additional corners and the possibility arises of centering the required information in one or all of these spaces available to us. This is theoretically possible in all cases where the front lens of the camera is not in direct apposition to the collimating lens of the image intensifier, and has proved practical in this instance where the optical axis of the lens is at right angles to that of the collimating lens of the image intensifier. Certainly, the reflecting mirror is in the optical path, but because this mirror is small enough to reflect all the circular field and nothing else, it can be bypassed to cast the oscilloscopic image precisely in one of the corners. This was the case in the unit illustrated in Figure 1.5 Technic Because the front lens of the camera is used, no additional shutter mechanism is necessary. This precludes short persistence oscilloscopes, and a long decay phosphor (P-7 or similar) must be employed. It is possible and certainly very desirable to avoid the bouncing ball effect of the writing dot, and this can be achieved almost to perfection with a storage-type oscilloscope. The available storage oscilloscopes are quite bulky, however, and a 20-milli-second blanking time from the end of one trace to the beginning of the next one is necessary. The oscilloscope utilized in this case is a CRT (cathode-ray tube) one-inch RCA long persistence (P-7) phosphor.6 To get maximal light intensity with long persistence, a light filter is required which separates the fast-decaying activating spot from the persisting spot. The P-7 phosphor has two light-intensity peaks, one at 4,350Å and one at 5,550Å. The 5,550Å spot is the long-persistence component. To separate the two spots, a Kodak Wratten filter No. 12 was used. This filter cuts off rapidly at 5.600Å, allowing a large portion of the longer wave-length spot intensity to pass, but effectively filtering the 4,350Å spot. This system allows good signal brightness with long persistence and prevents the bright activating spot from overexposing the film.