What is the phi phenomenon?
- The phi phenomenon is the optical illusion of perceiving a series of still images, when viewed in rapid succession, as continuous motion. First described by Max Wertheimer, one of the three founders of Gestalt psychology, defined this phenomenon in 1912. The human brain can only perceive about only 10-12 individual images per second, any faster, our brains blend the images together into motion.
What is the significance of 12fps?
- This was the first frame rate. Which gives/ plays back 12 frames per second (fps) with 12 intermittent periods of black as the film advances it will create an intolerable amount of flicker. To make the flicker not black Thomas Edison mentions that it would require 46 frames per second.
What is over cranking?
- This is when you record a fast frame rate than the final projection. D.W Griffiths was notorious for doing this, shooting as low at 2 frames per second, even Eddison ignored his own recommendation.
What is under-cranking?
- This is where you record a slower frame rate to the final projection.
What impact did the introduction of sound have on frame rates?
- Sound was generally such a huge technological advancement/ achievement that changed the way of film in a drastic way. Frame rates were required to be kept at a strict rate and was established in 1929 as 24 frames per second. It was made 24 frames per second as sound tracks didn't have the fidelity on 16 frames per second systems. They used 24 frames per second projection within a double bladed shutter which kept to the desired 48 projected frames per second.
Why 24 became the international frame rate standard?
- The audio track didn't have enough fidelity, so this way they settles for the next factor. 24 is a number which can easily be divided by 2,3,4 and 8. 24 fps became the international frame rate because it was cheapest option rather than going to 30 or 32 fps.
What issues surrounded bandwidth?
- The issues which surrounded bandwidth would be the fact that bandwidth used by the colour sub carrier which potentially interferes with the overall audio signals which cause inter modular beating. The solution to this would generally be that they would reduce the frame rate just by 0.1% which would make the frame rate 29.97 fps.
What was interlacing?
- This is where a picture is split into the upper field and the lower field. Each field would then be created within the screen one after the other within a comb like pattern.
How was the challenge of inter modulation tackled?
- To beat the intermodulation, or disortion caused by the hum generated within the electrical current, the refresh rate was set to that of the AC power which in the US (United States) is 60 hertz.
What is the significance of 60 Hertz and how does it relate to 30 frames per second?
- 60 Hertz is generally equal to having 60 frames per second and with this the screen will have full 30 frames per second.
What is the difference between VHF and UHF?
- VHF and UHF. VHF can be anywhere from 30 to 300 MHz which was the old black and white television sets. Whereas with UHF this can be anywhere from 300 to 3000 MHz and they were trying to introduce colour to the screens within television sets.
How was a colour standard arrived at?
- Luminescence and chrominance this is what is giving back when they break down the colour, broadcasters would be able to embed a colour signal as a subcarrier within a television signal. New colour TV's would pick up and interpret the colour subcarrier which would inevitably be ignored by the older black and white TV sets.
What challenge did bandwidth present to achieving a colour standard and how was this problem overcome?
- The bandwidth which was used by the colour subcarrier would potentially interfere with the audio signal which then caused intermodular beating. The overall solution to this would be to reduce the actual frame rate by .1% which phases the colour and audio signals so that they would never fully match up.
What was the fields per second ratio that was eventually developed as the standard in colour and what was the resulting frames per second ratio?
- Fields per second went from 60 to 59.94 and with 29.97 full frames per second.
What is PAL and why was it developed?
- This is a format which is used to solve colour problems which are plagued NTSC and would generally work with the 50 Hertz AC power which is used in Europe and everywhere else around the globe.
What was the fields per second and frames per second ratios of PAL and SECAM?
- PAL along with another similar format run at 50i for a standard effective 25 frames per second.
A)Produce a step by step guide to explain how we get from the 24 frames per second of film to a 60i video stream to be able to watch celluloid movies on video.
- First of all with 24 frames per second film this is slowed down by 0.1% and gives up 23.976 frames per second.
- If you were needed to make 4 frames of 23.976 to fit within 5 frames of 29.97. This would be done by splitting the frames into fields using a 3:2 pull-down.
- The first frame is captured onto three different fields - the upper, lower and then upper field - which is one and and a half frames. The next frame is then captured using the following two fields, lower and then upper.
- The next frame after then fills up the lower, then following upper and lower with the last frame which fills the upper and lower field.
B)What are the issues with the various conversion?
- The still overall resulted in the video streaming having Telecine judders every 3 frames which is generally/ especially noticeable within long slow camera movements.
How do modern digital cameras avoid the telecine process and with what effect?
- Modern digital cameras avoided the process involving telecine as they were recording 23.976 or straight 24 frame rates natively onto the hard drive but some workflows generally run through HDMI cables which are rated for 60i.
How are 24 fps films telecine'd onto SECAM or PAL 25 fps?
- With telecining film onto PAL or even SECAM's the process is/ much simpler. They used 2:2 pulldown which is the 24 frames per second footage which was sped up by 4% and each frame then transferred onto two different fields, upper and lower field. Due to the increased speed this raises the pitch of the audio noticeably by 0.679 semitones or a little more than a quarter.
Explain high frame rates and temporal resolution.
- 24 fps has generally been the standard fps used within narrative filming for nearly up to a century. Enterprising filmmakers now have tried to push temporal resolution or the frame rate even higher - meaning that they are trying to reduce the motion blur which will create a smoother and more realistic look within film.
What are the issues with higher frame rates in narrative filmmaking?
- Audiences have generally been able to warm up to the idea of high frame rates within narrative filmmaking. An example of a recent film with a high frame rate would be Peter Jackson's 'The Hobbit'. This film used 48 fps and audiences however didn't appreciate the change, in terms of how it looked, some audiences complained and commented that "the human actors seemed over-lit and amplified". A separate complaint would be that "it looked like a made-for-TV movie". Filmmakers such as Peter Jackson and or James Camera both push for higher frame rates to advance the way in which audiences watch narrative films.
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