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Math for Movies

Math for Movies. By: Trev Clapp. Before we get started. Working on films today requires a surprising amount of number crunching. We have become adept at a wide range of conversions -- but only with the use of the right software or calculator.

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Math for Movies

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  1. Math for Movies By: Trev Clapp

  2. Before we get started • Working on films today requires a surprising amount of number crunching. We have become adept at a wide range of conversions -- but only with the use of the right software or calculator. • Do you know how to convert film feet/frames to timecode, or how to convert non-drop frame code to drop frame? • Here are some formulas that I have compiled. Some came from such sources as Music Editing for Motion Pictures by Milton Lustig (1980); others from New York film editor Irving Oshman. • Each slide contains one or more math problems please do your best to try and answer them 

  3. 1) Convert 16mm footage to 35mm footage (all calculations assume 4-perf 35mm) Multiply 16mm footage by 2.5 Example: Convert 36 16mm feet to 35mm *Helpful Hint: Ignore the 16mm and focus on 36 and 2.5

  4. 2) Convert 35mm footage to 16 mm footage Multiply 35mm footage by 0.4 Example: Convert 90 35mm feet to 16mm

  5. 3) Use an ordinary calculator to add and subtract 35mm feet/frames One 35mm frame = 0.0625 feet (16 frames per foot). Multiply the frames part by .0625 to get their decimal equivalent. Or make a little chart of 35mm frame decimal equivalents Make a chart from 1 – 16 and multiply each number by .0625 if you don’t understand the above.

  6. Cont. 3b Example: Add 39+14 to 1769+07 Use the chart to find the decimal equivalent of 14 frames: .8750On a regular calculator, enter 39.8750 and press +Look up the decimal equivalent of 07 frames: .4375Enter 1769.4375 and press =The result is 1809.3125Look up the frame equivalent of .3125: 5 frames

  7. 4) Use an ordinary calculator to add and subtract 16mm feet/frames The 16mm decimal equivalent of one frame is .025 feet (40 frames per foot). Using that value, you can create a 16mm frame-equivalent chart similar to the one above and do 16mm calculations the same way.

  8. 5) Convert 35mm feet/frames to 16mm feet/frames • Example: Convert 16mm 83+38 to its 35mm equivalent. • Multiply 38 frames by .025 to get .95Multiply 83.95 by 2.5 to get 209.875Look up the 35 mm frame equivalent of .875, or divide .875 by .0625 to get 14

  9. 6) Derive the actual length of a reel in 35mm feet/frames minus the head leader • Add 1 frame to the LFOA (Last Frame of Action). • Subtract 12 from the footage. • Example: How long is a reel of 35mm film whose LFOA is 1827+13? • Add 1 to the frame count:13 + 1 = 14Subtract 12 from the footage: 1827 - 12 = 1815 • Note for sound editors: this is also the insert start mark of the reel.

  10. 7) Convert film frames to video frames • Multiply film frames by 1.25 • Drop fractional frame value (see #9 below). • Example 1: Convert 4 film frames to video frames • Example 2: Convert 7 film frames to video frames

  11. 8) Convert video frames to film frames • Multiply video frames by 0.8 • Drop any fractional value (see #9 below). • Example 1: Convert 5 video frames to film frames • Example 2: Convert 7 video frames to film frames

  12. 9) Rounding fractional frames • When converting between film and video, sound editing systems and dubbing controllers typically truncate fractional frame values (that is, they drop the fraction). • This means that the system picks the video or film frame that contains the leading edge of the frame being converted. • Film systems and Avid film systems follow the 3:2 telecine cadence and pick the nearest whole frame, which means that fractional values are rounded. • (Values of less than .5 are truncated, values of .5 and above are adjusted up to the nearest whole frame.)

  13. 10) Convert 35mm film feet/frames to time • Quick conversion -- good for short lengths: • Divide feet by 3, multiply quotient by 2 to get seconds. • Multiply any remainder by 16 to get frames. • Add the rest of the frames and divide by 6 to get quarter-seconds. • Example: Convert 19+03 to time • 19 / 3 = 6 (with 1 foot left over)6 x 2 = 12 seconds1 foot x 16 = 16 frames16 frames + 03 frames = 19 frames19 / 6 = approximately 3 quarter-seconds

  14. 10b)Convert 35mm film feet/frames to timeCont. • Standard conversion -- good for all lengths: • Multiply 35mm feet by 16 to convert to total frames (multiply 16mm feet by 40). • Add frames to (a) to get total frames. • Divide by 1440 to get total minutes (1440 frames per minute). • Multiply the answer by 60 to get seconds. Round off as needed. • Example: Convert 1240+13 to real time. • 1240 x 16 = 19840 frames19840 + 13 = 19853 total frames19853 / 1440 = 13.7868 minutes.7868 x 60 = 47.2083 seconds

  15. 11) Convert 35mm feet/frames to non-drop frame timecode • Convert feet + frames to total film frames (multiply feet by 16 and add any additional frames). • Multiply by 1.25 to get total video frames. • Divide by 108,000 to get total hours (60 minutes x 60 seconds x 30 frames = 108,000 video frames in one hour). • Divide remainder of (c) by 1,800 to get total minutes (60 minutes x 30 frames = 1,800 frames in one minute) • Divide remainder of (d) by 30 to get seconds. • Remainder of (e) is frames. (Truncate fractional values for sound editorial, round them for picture editorial. See #9, above.)

  16. 11) Convert 35mm feet/frames to non-drop frame timecode Cont. • Example: Convert 357+08 to 30-fps timecode. • 357 x 16 = 5712 • 5712 + 8 = 5720 total film frames • 5720 x 1.25 = 7150 total video frames • 7150 / 108,000 = 0 hours with a remainder of 7,150 frames • 7150 / 1,800 = 3 minutes with a remainder of 1,750 frames • 1750 / 30 = 58 seconds with a remainder of 10 frames

  17. 12) Convert non-drop frame timecode to drop frame timecode • Drop frame timecode adds 2 frames every minute, but not when the minute ends in 0 (minute 10, 20, 30, etc.). • Ignore hours. • Multiply minutes by 2 • Take the left-most integer of the original minutes column and multiply by 2. • Subtract (c) from (b). • Add the result, in frames, to the non-drop frame value. • Convert frames to seconds, as needed (30 frames = 1 second).

  18. 12) Convert non-drop frame timecode to drop frame timecode Cont. • Example: Convert 07:32:56:27 non-drop to drop frame timecode • Double the minutes: 32 x 2 = 64 • Double the left-most minutes integer: 3 x 2 = 6 • Subtract: 64 - 6 = 58 • Add the result to the frames column: 27 + 58 = 85 • Convert to seconds: 85 / 30 = 2 with a remainder of 25, or 2 seconds 25 frames.

  19. 13) Convert drop frame timecode to non-drop frame timecode • Ignore the hours column. • Double the minutes column. • Double the left-most integer of the minutes column. • Subtract that from the doubled minutes. • Continue as in the previous slide, but subtract from the frames column

  20. 14) Convert non-drop frame timecode to 35mm feet and frames • A) If the hour is used as a reel number, then ignore hours. If not, multiply hours by 86,400 to get total film frames.(90 feet per minutes x 60 minutes per hour x 16 film frames per foot = 86,400). • B) Multiply the minutes column by 1,440 to get total film frames.(90 ft. per min. x 16 film fr. per foot = 1,440). • C) Multiply seconds by 24 (24 film frames per second). • D) Convert video frames to film frames. • E) Add (b), (c) and (d), or add (a), (b), (c) and (d), as appropriate, to get total film frames. • F) There are 16 film frames per foot. Convert to feet and frames, as needed.

  21. 14)Convert non-drop frame timecode to 35mm feet and frames Cont. • Example: Convert 02:03:59:10 to 35mm feet and frames(assume the hour represents a reel number) • Ignore hours3 x 1,440 = 4,32059 x 24 = 1,41610 video frames x .8 = 84,320 + 1,416 + 8 = 5,744 film frames5,744 / 16 = 359

  22. 15) Convert drop frame timecode to 35mm feet and frames. • First convert to non-drop frame (see #13 above). • Then use the formula outlined in number 14 to convert to feet/frames.

  23. 16) Convert a 24 fps audio file to fit non-standard film speed picture • Divide the non-standard film speed by 24. • Use the AudioSuite "Time Compression Expansion" module.Enter the value from (a) into the "ratio" box to create an audio file that will run in sync with corrected pitch. • Example: Picture was shot at 12 fps, but audio was recorded at 24 fps. By how much do you have to change the speed of the audio to match the picture?

  24. 17) Change the pitch of a 24 fps audio file to fit non-standard film speed picture • Divide 24 by the non-standard speed (opposite of #16). • Use the AudioSuite "Pitch Shift" module.Enter the value from (a) into the "ratio" box and deselect "Time Correction." • Example: same as #16 above. Picture was shot at 12 fps, but audio was recorded at 24 fps. By how much do you have to change the pitch to match the length with the appropriate pitch change?

  25. Answers Yo! • 36 x 2.5 = 90 35mm feet • 90 x 0.4 = 36 16mm feet 3) 1=0.0625 2=0.1250 3=0.1875 4=0.25 5=0.3125 6=0.3750 7=0.4375 8=0.5 9=0.5625 10=0.6250 11=0.6875 12=0.75 13=0.8125 14=0.8750 15=0.9375 16=1

  26. More Answers Yo! • 3b) 1809+05 • 4) there was no question sorry • 5) 209+14 • 6) The answer is 1815+14 • 7a) 4 x 1.25 = 5 The answer is 4 film frames = 5 video frames • 7b) 7 x 1.25 = 8.75 Dropping the fraction, the answer is 8 video frames. • 8a) 5 x .8 = 4 The answer is 5 video frames = 4 film frames • 8b) 7 x .8 = 5.6 The answer is 5 film frames • 9) there is no question sorry • 10a) The answer is 19+03 = 12 3/4 seconds • 10b) The answer is 13 minutes and 47 seconds • 11) The answer is 00:03:58:10 • 12) The answer is 07;32;58;25 • 13) there is no question sorry • 14) The answer is 359+00 • 15) there is no question sorry • 16) Target rate divided by original rate = conversion rate 12 / 24 = .5Enter .5 as the "ratio" in AudioSuite's Time Compression Expansion module.

  27. Even More Answers Yo! • 17) 24 / 12 = 2.0 Enter 2.0 in the ratio box in AudioSuite's "Pitch Shift" module to render the audio file as the equivalent of 12 fps with its pitch raised accordingly. • 18) Did you actually look back to see if you missed a question?

  28. Work Cited • All info presented to you came from:http://www.editorsguild.com/v2/magazine/Newsletter/JanFeb03/tip_math.html • Now you know how math can be involved with movies!!

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