Most projects today are being shot in various kinds of digital formats. Digital media is cheap and reusable, therefore the shooting ratio is no longer a worry for many producers or directors. But traditionally larger budget films are still shot on 35mm. 16mm is mainly used by students or the occasional indi director (like Aronofsky on Black Swan). For those occasions when you need to know exactly how many takes you can afford to shoot per setup on day x of the shoot, here are a few tips:
Shooting Ratio tells how many feet of film stock a production can afford to expose to get one foot of film of the finished project. Like any ratio it looks like this – x:1 (x to one). So if the ratio is 10:1 that means 10 feet of film stock are available for 1 foot of finished film on screen. Alternatively ratio can be done on time – minutes of footage shot for one minute of screen time.*
A few important conversions to know:
35 mm runs at 90 ft/min (for cinema 24 fps)
16 mm runs at 37.5 ft/min (for video 25 fps)
16 mm runs at 36 ft/min (for cinema 24 fps)
There’s another less precise way to convert feet in minutes or vice versa, by knowing that a roll of 16mm measures 400 ft and runs for about 11 minutes (at 24 fps) and a roll of 35mm measures 1000 ft and runs for about 11 minutes (at 24 fps). Always check with the Clapper Loader the length of each roll in use. They might use short ends or there are in fact 35mm rolls 400 ft long.
There are a few ratios you’ll need to calculate:
The Scheduled Ratio – takes into account what has been allocated in the budget for film stock to complete the film. This original ratio is calculated on the estimated length of the project (check out timing scripts). For instance, you estimate the film to run for 90 minutes and the budget allows for 81 cans of 35mm stock. Using the conversions above,
81 cans = 81 x 1000 ft = 81000 ft of stock (1 can of 35 mm = 1000 ft)
81000 ft = 81000 ft : 90 ft/min = 900 min (35 mm conversion feet to minutes 90 ft/min)
900 min (of budgeted stock) : 90 min (of timed script) = 10:1 ratio
This means that for each minute of screen time you can shoot 10 minutes of footage – or for each foot of finished film the production has allocated 10 feet of unexposed film stock. Directors keep this in mind when they plan their coverage and for less important scenes they prefer to shoot under ratio to save stock for more dramatic scenes that need extra coverage or more takes.
The Daily Ratio – should be the same value or lower than the Scheduled Ratio. If it’s too much under this value it shows under-coverage and the Director needs to be notified. As I mentioned earlier Directors might under-cover on purpose saving stock for other more important scenes.
To get the Daily Ratio you need to time your daily script pages and add the total feet of film exposed that day. The total length of film exposed in a day is usually given to you by the Clapper Loader at lunch, if they split rushes, and at the end of the day.
Let’s assume on a day you covered 4 minutes of screen time and used about 4 cans of stock, 3960 feet to be precise.
3960 ft : 90 ft/min = 44 min (length in minutes of the stock exposed that day)
44 min (exposed film) : 4 min (screen time) = 11 : 1 ratio
This Daily Ratio goes into your Continuity Daily Progress Report. As it is higher than the Scheduled Ratio the Director and the Production Department need to be notified so on any of the following shoot days the coverage needs to drop for the ratio to get closer to the Scheduled Ratio – otherwise the production might run out of film stock before the end of the shoot.
Average Ratio – at the end of a week do a simple average of each day’s shooting ratios. It’s always good news when the Average Ratio is close to the Scheduled Ratio, it means the production is running efficiently and there’s no danger of running out of stock.
To calculate this average add all your ratios from that week and divide that number by the number of days worked that week. For instance, if you shot everyday Monday to Friday, you will have 5 days, 5 shooting ratios. Add the 5 shooting ratios and divide the sum by 5. The result is your Average Ratio.
*NB – I prefer to do my ratio in minutes. It makes no difference to the actual final ratio but I find it easier to work with minutes rather than feet – exact same technique when ratio done in feet.