MTF – Modular Transform function – sounds more complicated than it is and is something any one involved in the workflow of film should get their heads around!
Modular means in bits – like the modules for subjects being broken down rather than all in one go…
Transform – in context describes the flow from one of these modules to another
Function – the way it operates
So ultimately what we are looking at is a workflow – this could be anything from a factory line to filmmaking to an episode of Total Wipeout (or any challenge based gameshow)
In fact lets keep going with Total Wipeout…
If the thing we are measuring is contestants and the modules are each assault course/challenge then the MTF of the whole thing is 1. Only 1 contestant gets through – they start with 24… but even if you put 300 contestants at the beginning (like they do in Takeshi’s Castle) you would still only get 1 out of it as the final challenge only allows 1 to come through at the end.
If that final challenge was put at the start or in the middle of the show their would still be only 1 contestant.
This is the main concept of MTF that the bit that allows the least through – will always be the maximum you can get out at the end…
So with digital cinematography cameras what are the modules…
- Light from sun to object
- Object to whatever may be in front of the lens (matte box)
- Lens to Sensor
- Sensor to compression
- Compression to connecting to storage device
- Storage device’s read and write speed
- The compression of data to usable rushes
- Rushes into post workflow software’s architecture
- Final cut format
- Distribution format
- Projector light
- Light from screen to Human eye
- Human eye to brain
So let’s put this in an extreme way – you shoot on an imax camera 72mm format – really take care to have as little loss all the way along – then your masterpiece is screened only once to a bunch of blind people… MTF 0
Only the sound got through – so knowing that bit may as well made radio
Or more realistically – you shoot on a RED at 4k resolution with great lenses – your post workflow caters for 4k – your short film then only goes through a 2k projector at a few festivals and then goes on youtube at 720p…
Your project is only ever going to look as good as the weakest part of the chain – so make sure you think of that as DP when considering quality control of your image – as ultimately it is your brain trying to maintain a concept through this incredible but convoluted process all the way to the brains at the other end – here is a diagram I did…
Due to the fact that you are always losing just in the process of going from beginning to end regardless – there is a theory that you should always try and start off with double to get half out… so if you are aiming for a true 4K resolution really you would need all the bits to be shooting 8K to have that true unlossed quality of 4k at the end…
Also – people who really know how to measure this stuff even consider the loss of bandwiths of light in the suns spectrum as it goes through gases that slightly filter it before it gets to earth… this might get to a stage where it is beyond practical – but the main thing to remember is your weakest part in the workflow is the max you will be getting through at the other mind you want to share your vision with!