There has been much discussion among the pages of International Movie Making concerning the Super-8 plastic pressure plate, and how to improve it, including an excellent analysis of a make it yourself gate from George Morice. By the time his article hit my mailbox I had already purchased the Frame-Master direct from Germany six months earlier. The Frame-Master, a small polished silver metal piece that is inserted into the cartridge quite easily over the plastic pressure plate, advertises itself as providing a marked improvement in picture sharpness and steadiness.
        Despite the malign perception of the Super-8 plastic pressure plate designed by Kodak, it is really an engineering marvel. What makes this a marvel is the fact that it works so well and so consistently. The Kodak cartridge system was designed for the masses, an attempt to produce at an affordable price a simplified movie system. And much like the Model T Ford, or perhaps the Volkswagen Beetle, the affordable and simple system worked and the masses bought millions of the little black cartridges.
        The so-called plastic pressure plate, which is built into the cartridge, isn’t actually a pressure plate at all. It’s designed to create a channel for the film to flow through, a channel that stays at a fixed width of approximately .007 inch (about .002 inches thicker than Kodachrome film). The film is not held with constant force against the plastic but merely slides around in the channel. The simplicity of this system is amazing, and the system works because it is based upon the principles of depth of focus (not to be confused with depth of field).
        Now follows the scientific bit, explaining the two. Depth of field is the amount of the scene in front of the lens that will appear acceptably sharp. It increases with smaller f/stops, wider angle lenses and the further distance from the camera the subject is. This illustration from the Focal Encyclopedia of Photography shows what I mean.

        For the really technical, use the following formulae to establish depth of field: (all measurements must be in the same units)

        For those who want to delve more deeply into the esoteric properties of depth of field there are vast numbers of books on optics to give many a sleepless night! Now for depth of focus, which is the important one as far as we are concerned here. This is the amount of ‘play’ a film surface can have yet still remain acceptably focused. When a lens is focused on an object in front of it there is one position where the image is sharpest. This is obviously where the film should be held – the film plane. The sharpness falls off as the film is moved away from this position of exact focus, but there is a certain range of movement in which the eye cannot detect the difference between a sharp and a very slightly blurred image. That zone of sharpness is called the depth of focus.
        Like the depth of field, the depth of focus depends on the circle of confusion, (which I won’t confuse you with now), the lens aperture and the distance between the lens and the image. Conveniently the depth of focus extands the same amount in front of the film plane as it does behind it, and for the formula lovers:

        All this means is that the law of optics allows the film to “waggle” about a bit and still retain an acceptaqbly sharp image. A boon for Kodak’s Super-8 cartridge as the depth of focus for Super-8 filming is wide enough so that the inconsisitencies in the focus created by the gap in the channel will not be seen on the screen. There is a problem that arises with the channel design when the camera is first started, when the the initial frames appear to go in and out focus. This is due to the fact that the film having been unwound from its roll and sitting in place near the film gate for some time has a different curl to it than the film coming directly off the roll. This difference in curl may make the film slide around in the channel more than usual, which causes the noticeable effect of “breathing focus.”
        The Frame-Master must narrow the gap in the channel, or reduce it to nothing at all, because true to the advertiser’s claims, there is a noticeable improvement in picture quality, especially with Ektachrome 7240. Perhaps the Ektachrome is a thinner film than Kodachrome and this makes the Frame-Master perform best with this stock, or perhaps due to the Ektachrome having an inherent grainy look to it, the difference is more obvious to the eye. Whatever the case, Ektachrome 7240 was always a half blessing. Never designed for Super-8 in the first place, but for 16mm, Kodak released it a few years ago as something to give the Super-8 user when Ektachrome 160, which had been designed for Super-8 use, ceased manufacture. The problem with 7240 is the constant grain and lack of sharpness, especially in low light filming which is what the stock is intended for anyway.
        With the Frame-Master, Ektachrome 7240 acts like a new film stock – the difference is that amazing! The grain, and the lack of sharpness, are almost completely gone. It now much more closely resembles the superior Kodachrome in every way. I am no longer fiddling with the focus knob on the projector because the picture is not sharp. To me, this is the biggest breakthrough in years. The improvement in picture quality when using Kodachrome is not as noticeable, and often not noticeable at all. Still, there is never a cartridge that goes into my camera without the frame-master inserted into it.
        Designer and manufacturer of the Frame-Master in Germany, Gottfried Klose, rekons that his invention has a benefit particularly in the last third of each 50 ft roll, because the rotation speed of the film in the unexposed side of the cartridge increases greatly, thus causing much uncontrolled movement in the gate area. Users may have noticed that there is a noise increase towards the end of the film, but the Frame-Master plate helps to calm the film and keep the image steady, not only from side to side but up and down.
        Herr Klose also supplies a repair and customer support service for Nizo, Bauer, Eumig, and Beaulieu equipment. Visit his website at www.film-super8.de for details.

---  A collaborative effort by Roy Salmons and Chris Cottrill
        E-mail:  ^{chris_cottrill@yahoo.com}
 

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