TECHNICALITIES - why most amateur film-to-video transfers are bad

There are important differences between film and tv systems that have to be taken into consideration when trying to transfer from film to video or DVD.

Most amateur film is shot and projected at 16 or 18 frames per second (fps). The speed was standardised at 18 fps when Super 8mm was introduced in the 1960`s.

TV systems in Europe (and many other places around the world) using PAL or SECAM colour systems scan an image of 625 horizontal lines at 50 fields per second. This scanning is what is referred to as interlaced scanning because one vertical scan of the image records lines 1, 3, 5 etc and the next scan records lines 2, 4, 6 and so on. This is done to reduce bandwidth of the transmitted image, the flicker frequency being 50 but the frames per second being 25.

There are two ways to achieve flicker-free film to video transfers. One is to transfer on a frame by frame basis (which is very slow and a lot more trouble to arrange but can give much better results) and the other is to run the projector as normal but with adjustments to the running speed.

Here is a YouTube example of a Standard 8mm frame by frame transfer - CLICK HERE

Here is a YouTube example of a Standard 8mm real-time 16.66fps transfer - CLICK HERE

Here is a YouTube example of a Super 8mm real-time 16.66fps transfer - CLICK HERE

Obviously neither 18 nor 16 will divide evenly into 50 and the three-bladed shutter on the normal 8mm projector will cause a flickering effect if running at 16 or 18 fps.

However, altering the projection speed to 16.66 (sixteen and two thirds) fps will divide into 50, giving the answer 3. And so, reducing the projector speed from 18 fps or increasing from 16 is the answer to that little problem. (Making it happen might be a bit more difficult, see later)

The result is that each frame of film will be scanned by 3 tv fields.

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*In the USA, Canada, Japan and anywhere else that uses the NTSC standards for broadcasting the frame rate will be around 30 frames per second (actually slightly less but very close) with a field rate of around 60 fields per second. This can be accommodated by increasing the projector speed to around 20 fps, each frame of film being scanned for 3 fields. On a film shot at 16 fps this increase in running speed might be unacceptable to some people. Running film at 15 fps would require a four-bladed shutter or frame by frame methods. A two-bladed shutter might work for 60 field tv but I haven`t tried it, my experiments are all based on 50 field systems.

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When transferring film shot at 24 fps you hit another little problem. Most amateur film projectors have a three-bladed shutter. Fine for transferring at 16.66 fps but not at all suited to the faster speed. For that the ideal would be a two-bladed shutter and a projector running speed of 25 fps for the PAL or SECAM systems, or use of the frame-by-frame methods.

By controlling the projector speed to suit the tv system you can at least avoid the flicker problems that afflict most amateur transfers ( and a lot of so-called “professional” efforts that you get charged £40 per half hour to suffer).

Acceptable results may possibly be obtained by using a small back-projection screen or projecting a small image on a white card and focusing a camera on the image but you must remember that the image is passing through two lenses and the quality of the image will suffer as a result. It`s far better to focus that video camera down onto the film itself using macro photography techniques. It`s not as difficult as it might at first seem to be.

 

COMMON PROBLEMS WITH 8MM : The film hardware isn`t the only little problem you might come up against. There are issues associated with the film itself. CLICK HERE for more information.

TECHNICALITIES - choosing a projector

The only source of 8mm projectors today will be the second-hand market. There may be some manufacturers of these machines still producing them but they`ll be very expensive. For most of us the first port of call will be ebay, but it can be a risky business and you need to be wary. I`ve bought quite a few projectors over the years and my experience has been that private sellers tend to be a lot more honest about the condition of the machines than business sellers who have a tendency to tell you something is in very good condition and when it turns up it`s decidedly not the case.

Very often it doesn`t matter to me if my intention is to just use the components but if you`re expecting a fully functioning machine that has been looked after you may well be disappointed.

Basically, don`t pay too much. Transport costs can be high, frequently £15 to £25 and some sellers pitch the postage cost higher than necessary to improve their profit.

You could try car boot sales but I`ve not seen many projectors at these events. At least you can avoid postage costs. If they want to charge you for just having a look round a car boot sale I`d give it a miss if I were you.

The ideal machine will be one that allows you to fit a camera behind the projector gate, mounted upside down so that the image on the screen will be the correct way up. It needs to be aligned properly or the focus will suffer (when you use extension tubes on the camera you have entered the realm of macro-photography and focusing will be critical.

The machine below is a Eumig P26. It has a large lamp housing that can easily be removed and both the feed and take-up spools are at the front of the machine, leaving the back clear for mounting the camera. The disadvantage of this particular model is that it has only a two bladed shutter so isn`t suitable for continuous transfer at 16.66 frames per second. Ideal for frame by frame work, though.

Eumig P26 - front view without lamphouse (42K)

The image above shows the Eumig P26 with its lamp house removed. Machines like the later Eumigs with a take-up hub at the rear of the projector and much smaller lamphouses are not as good from the modification point of view but are generally less ancient. Old machines may only need a bit of cleaning up and lubrication to bring them back to usable condition and they are often better made than the later examples.

 

TECHNICALITIES - what type of camera to use

If you go down the simple setup route, projecting on a back-projection screen or white card fixed to a wall then you may just use a normal camcorder. Most have close-up focusing facilities and many can work at a fixed shutter rate. (Camcorders often have adjustable exposure rates, equivalent to the mechanical shutter speeds on film cameras but you need to be able to fix the camcorder`s exposure at its normal rate of one-fiftieth of second per field for PAL/SECAM or one sixtieth of a second for NTSC) The camcorder instruction manual should tell you what you need to know.

If you have access to a CCTV camera of the type use for surveillance then you often find they have a set of DIP switches or an on-screen menu system, to control exposure and AGC (automatic gain control) and, because they normally accept standard CS and C-mount lenses, they are ideal for use with extension tubes for macro photography. More about extension tubes later.

In addition they often use one-third or half inch diameter CCD image pickup devices that provide a picture quality and light sensitivity that many recent consumer cameras with their tiny little CCDs cannot match. For macro photography you need a sensitive imaging device. And a lot of patience. A camera with a claimed horizontal image resolution of 400 lines or more would be good. Suitable CCTV cameras can be found at reasonable prices second-hand on ebay.

Shown below is the back panel of a JVC C1360. The camera has an S-video (Y/C) output,which gives better image quality than a BNC video output. But these cameras are somewhat large making it more difficult to fit them in the lamp house area of a typical 8mm projector. There are board cameras available which measure no more than two inches wide or high but many of them don`t have C mounts or on screen controls.

TECHNICALITIES - controlling the projector speed

Ideally you need a projector that will allow you to vary the running speed to that which you need but that will also run at that speed without the need for constant adjustment. As always, ideals are a bit difficult to find. Most amateur projector equipment will have either variable speed motors (a.c., d.c., mains or low voltage) or mains voltage induction motors, often what are called shaded pole motors which are cheap to make but inefficient, and run hot. Eumig sound projectors often used shaded pole motors. Once warmed up and running the induction motor will keep its speed quite well.

If you have the knowledge and software you can monitor the speed of a projector using a computer, taking a pulse from the projector to an input on the computer which then will count the number of pulses per second and calculate the speed. Otherwise you`re stuck with the old mechanical methods. To be able to see how close to the ideal speed you`re getting you need a visual indication of the speed. A projector with an inching knob that makes one turn every frame of film, preferably at the rear of the machine, is the best indicator.

The inching knob is normally used when loading a film to check that the film has been threaded correctly. One turn per frame is the usual arrangement but it can be more.

To illuminate the knob you`ll need three or four mains neon indicator lights of the type that are used to show electronic devices are switched on. They are rated at 220/240 Volts AC and contain a resistor that enables their use with mains electricity. These can be bought for around £1 each at electronics shops (Maplins in the U.K.) and need to be wired in parallel, mounted together on an assembly of some kind and connected to the mains electricity supply.

*IT HAS TO BE SAID: BE VERY CAREFUL WHEN DEALING WITH MAINS ELECTRICITY!

The reason neon lamps are used is because they switch on and off very rapidly at mains frequency. You`ll need four to get a bright enough light to be able to see the effect well enough. The 50 cycle mains supply (60 cycle in the USA) is the reason why the tv systems of the various continents are set at the rate they are. These days it wouldn`t matter because electronic devices can accommodate different systems with ease but back in the 1930s when television was being developed it was deemed necessary.

A form of stroboscopic indicator needs to be fixed to the inching knob. A circular disc divided into six equal sectors (for 50 cycle mains) or even a single white mark on the end of the knob itself will do. What matters is that when the neon flashes the indicator will appear to be stood still at the correct running speed and will move either backward or forward when the speed is not exactly correct. (see next web page for possible designs)

In the absence of an inching knob you may be able to use the rotary shutter inside the projector. A three-bladed shutter will appear stationary at 16.66 fps(using PAL/SECAM) or at 20 fps (using NTSC).

If your projector has a variable speed control that can slow the machine to the required rate then you have your speed control already to hand.

If you`re going to use a projector with an shaded-pole induction motor then a continuously variable autotransformer would be a good idea. These handy devices enable you to control very precisely the voltage reaching your machine and it`s easy to adjust the voltage whilst keeping an eye on the inching knob strobe.

I should point out that this method is okay with shaded-pole induction motors but the more powerful capacitor-start and capacitor-run motors will not be suitable for voltage control, their speed being determined by the mains frequency.

The picture below shows a typical variable transformer. This one is made by Dimmerstat. Turning the rotary control increases or decreases the AC voltage fed to the projector.

A Dimmerstat rotary auto-transformer. Housed in a home-made box. The plug goes to the mains supply and the projector is plugged into the trailing socket.

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