“Frame by frame” and “Flicker Free”

These are the buzzwords of the cine transfer market but what about colour space and dynamic range that have as much if not a greater impact on the end visual quality.

The full film to video chain is important when transferring film to achieve the best result.

Flicker free and frame by frame is the terminology used by many transfer companies but what exactly do they mean and is that all there is to it.

Let’s look at flicker free first. Well this term comes from the effect of just pointing a camera at the projection of the film, because the film is running at typically 18 frames per seconds and a video camera runs at 25 frames per second you get an annoying banding or flicker because of the frequency differences, this can be overcome simply by changing the frequency of the cameras shutter to match that of the projector, it doesn’t give good quality on its own but it stops the flickering, but don’t confuse this flicker with relatively low frame rate you get from film there is nothing you can do for that, but it’s the effect that gives cine film part of its unique charm and has been replicated many time in the movies and adverts as it evokes an era or gives a nostalgic look that we all love and can relate to.

“Frame by frame”

This is exactly what it says so for each frame of film there is a unique frame of video, but if we play this in real time it will run too fast again because the film rate is only 16 to 18 frames per second (fps) and video is 25 here in the UK or 30 in the USA.

So frame duplication must take place so the film will appear to run at the correct speed, not ideal but it’s really the only way to do this as the film rate is fixed when recording. Does it look better than an interleaved video some can see a slight improvement but this is not the full picture (excuse the pun).

So if you get both of the above right will the quality of the transfer be good, well not exactly there are other factors to consider the lens, light source and imaging device, colour compression and recording mechanisms all need to be good. Film has a wider dynamic range than video so, it’s not possible to resolve it all, there may be some loss of highlight and or shadow detail, poor systems will loose lots of range due to the use of small sensors, lack of knee (this is how the camera handles highlights – more of which I will go into in a future article) and a low dynamic range, the pictures will be sharp but there will be no detail in the brightest and darkest parts of the scene this is typically from systems using machine vision cameras and low cost camcorder based systems.

Bit Depth

Another aspect is the bit depth, a lot of low quality systems record in 8 bit 4:2:0 which means that the colour range is limited, it’s fine for properly coloured and exposed film, but not good if your film is badly coloured and too dark, the technician needs to make adjustments and colour corrections and this can only be done if the recordings are in at least 10 bit 4:2:2 colour space. All systems need a lens and some form of lighting so the image from the film can be transferred to the electronic imager, these days most illumination is LED as its bright and very low heat, that’s great for film because if it stops in the gate it won’t burn unlike a tungsten bulb that will fry your precious film after only a few seconds.

The problem with LEDs is that they have a low CRI this means parts of the colour spectrum can be missing, good LEDs use arrays so you get more spectrum with less holes making wide colour correction achievable. Obviously the lighting needs to be even and soft to help hide scratches and the like. The lens also needs to be good, correct lensing needs to be employed because essentially you are focusing on an small cell.

The Human Element

Another component of a cine system is the technician, he or she needs to have a good understanding of the system in use, the quirks of small gauge film and how to effectively transfer it optimising the colour, contrast and sharpness.

Film

So that just leaves the film, most film by now has been spliced onto larger reels and projected numerous times so it will have picked up dust, dirt, projector oil, finger prints etc. so it really needs to be carefully cleaned before transfer it could be transferred as is but you would see lots of dirt on screen as the film frame is so small minute particles are magnified many times, cleaning properly is typically a process of running the film through a soft cloth soaked in a film cleaning solution these dry rapidly and don’t do any damage to the emulsion of the film in fact they help preserve the films. Other systems can be used such as sonic cleaners, PTR cleaning rollers and wet gate systems all with similar end results.

I hope this has given a little insight into cine film transfers, there are many systems out there some cobbled together with mirrors and projectors right up to million pound monsters, all transfer film just some are better than others. The only real way to see if you’re happy with the transfer is to get test reel done and see the results for yourself.

Chris Gillooly