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. Unfortunately, there are going to be times when the computer is unavailable or the special timecode calculator is on the fritz. Do you know how to convert film feet/frames to timecode, or how to convert nondrop frame code to drop frame?
Here are some formulas that I have compiled over the years. Some came from such sources as Music Editing for Motion Pictures by Milton Lustig (1980); others were taught to me by the late New York film editor Irving Oshman. The rest, well, I figured out.
So file them away in your editing kit. You never know when the next energy crisis will hit, and you'll have to do your cipherin' the oldfashioned way.
1. Convert 16mm footage to 35mm footage (all calculations assume 4perf 35mm):
Multiply 16mm footage by 2.5
Example: Convert 36 16mm feet to 35mm
36 x 2.5 = 90 35mm feet
2. Convert 35mm footage to 16 mm footage:
Multiply 35mm footage by 0.4
Example: Convert 90 35mm feet to 16mm
90 x 0.4 = 36 16mm feet
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:
1 
= 
0.0625 

9 
= 
0.5625 
2 
= 
0.1250 

10 
= 
0.6250 
3 
= 
0.1875 

11 
= 
0.6875 
4 
= 
0.25 

12 
= 
0.75 
5 
= 
0.3125 

13 
= 
0.8125 
6 
= 
0.3750 

14 
= 
0.8750 
7 
= 
0.4375 

15 
= 
0.9375 
8 
= 
0.5 

16 
= 
1 
Example: Add 39+14 to 1769+07
Use the chart to find the decimal equivalent of 14 frames: .8750
On a regular calculator, enter 39.8750 and press +
Look up the decimal equivalent of 07 frames: .4375
Enter 1769.4375 and press =
The result is 1809.3125
Look up the frame equivalent of .3125: 5 frames
The answer is 1809+05
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 frameequivalent chart similar to the one above and do 16mm calculations the same way.
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 .95
Multiply 83.95 by 2.5 to get 209.875
Look up the 35 mm frame equivalent of .875, or divide .875 by .0625 to get 14
The answer is 209+14
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 = 14
Subtract 12 from the footage: 1827  12 = 1815
The answer is 1815+14
Note for sound editors: this is also the insert start mark of the reel.
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
4 x 1.25 = 5
The answer is 4 film frames = 5 video frames
Example 2: Convert 7 film frames to video frames
7 x 1.25 = 8.75
Dropping the fraction, the answer is 8 video frames.
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
5 x .8 = 4
The answer is 5 video frames = 4 film frames
Example 2: Convert 7 video frames to film frames
7 x .8 = 5.6
The answer is 5 film frames
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.)
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 quarterseconds.
Example: Convert 19+03 to time
19 / 3 = 6 (with 1 foot left over)
6 x 2 = 12 seconds
1 foot x 16 = 16 frames
16 frames + 03 frames = 19 frames
19 / 6 = approximately 3 quarterseconds
The answer is 19+03 = 12 3/4 seconds
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 frames
19840 + 13 = 19853 total frames
19853 / 1440 = 13.7868 minutes
.7868 x 60 = 47.2083 seconds
The answer is 13 minutes and 47 seconds
11. Convert 35mm feet/frames to nondrop 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.)
Example: Convert 357+08 to 30fps 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
The answer is 00:03:58:10
12. Convert nondrop 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 leftmost integer of the original minutes column and multiply by 2.
 Subtract (c) from (b).
 Add the result, in frames, to the nondrop frame value.
 Convert frames to seconds, as needed (30 frames = 1 second).
Example: Convert 07:32:56:27 nondrop to drop frame timecode
Double the minutes: 32 x 2 = 64
Double the leftmost 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.
The answer is 07;32;58;25
13. Convert drop frame timecode to nondrop frame timecode:
 Ignore the hours column.
 Double the minutes column.
 Double the leftmost integer of the minutes column.
 Subtract that from the doubled minutes.
 Continue as in #12, but subtract from the frames column.
14. Convert nondrop frame timecode to 35mm feet and frames.
 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).
 Multiply the minutes column by 1,440 to get total film frames.
(90 ft. per min. x 16 film fr. per foot = 1,440).
 Multiply seconds by 24
(24 film frames per second).
 Convert video frames to film frames.
 Add (b), (c) and (d), or add (a), (b), (c) and (d), as appropriate, to get total film frames.
 There are 16 film frames per foot. Convert to feet and frames, as needed.
Example: Convert 02:03:59:10 to 35mm feet and frames
(assume the hour represents a reel number)
Ignore hours
3 x 1,440 = 4,320
59 x 24 = 1,416
10 video frames x .8 = 8
4,320 + 1,416 + 8 = 5,744 film frames
5,744 / 16 = 359
The answer is 359+00
15. Convert drop frame timecode to 35mm feet and frames.
 First convert to nondrop frame (see #13 above).
 Then use the formula outlined in number 14 to convert to feet/frames.
Math For Pro Tools
16. Convert a 24 fps audio file to fit nonstandard film speed picture:
 Divide the nonstandard 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?
Target rate divided by original rate = conversion rate
12 / 24 = .5
Enter .5 as the "ratio" in AudioSuite's Time Compression Expansion module.
17. Change the pitch of a 24 fps audio file to fit nonstandard film speed picture:
 Divide 24 by the nonstandard 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?
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.

EQUIVALENCIES
1 film frame @ 24 fps = 2000 audio samples at 48 kHz
1 film frame @ 24 fps = 1837.5 audio samples at 44.1 kHz
1 second @ 24 fps = 0.6 of a foot in 16mm = 1.5 feet in 35mm
1 minute @ 24 fps = 36 feet in 16mm = 90 feet in 35mm
1 film frame = 1.25 video frames
1 video frame = 0.8 film frames
1 hour real time = 00:59:56:12 NDF TC = 01;00;00;00 DF TC
90 35mm feet = 1 minute = 01;00;02 drop frame timecode
1 foot = 16 frames in 35 mm = 40 frames in 16 mm
3 35mm feet @ 24 fps = 2 seconds in real time
3 16mm feet @ 24 fps = 5 seconds in real time


Copyright © 2003, All Rights Reserved, The Motion Picture Editors Guild, IATSE Local 700
