25p revisited

M

morgan_moore

Major Contributor
Im just working up to my first big conversion

And obviously considering the 7d too

What is the thoughts on this,

30

Doubled is 60p

Divided by 2.5

=24p

Sped up by 104%

ie one hundred min plays over 96ish mins

= 25p

ie there should be best motion achievable in exchange for a slight change in the speed of 'reality'

Am I correct that 24p film are conformed to 25/50 broadcast by such 'speeding up'

S
 
usually that's what happen, 24 => 25 by speeding up 104%

30 => 24 by 30 =>60 and then 2:3 pulldown to achieve is certainly a way that works, but probably twixtor gets a better result
 
I've tried to find countless 24 to 25p comversions and only have ever read that it is simply sped up.

I doubt there's any other way, if there is I could've used it back in the D90 days.
 
Im doing it (tests) now

The advantage is just use nearest frame - there should be one ?

No interpolation = fast and also no funny behaviour

S
 
no it will just play faster

a one hour film would take 96 mins to play, no pauses

like running film through a projector with the projector running a little fast

---

so far it is all looking like a POS, im just doing a 25p best conversion in FCP

S
 
morgan_moore said:
no it will just play faster

a one hour film would take 96 mins to play, no pauses

like running film through a projector with the projector running a little fast

---

so far it is all looking like a POS, im just doing a 25p best conversion in FCP

S
Click to expand...
Speeding up and using nearest frame are two different things, anyway
 
no your not getting what Im getting at - im talking about doing both

its about phase difference, and what numbers divide

24 may be a better fraction of 30 than 25

so if a 24 conversion is better than as 25 conversion the best way to get to 25 could be to make a 24 conversion and then speed it up to 25

Meaning better 'phase allignment' at the exchange of a very slightly undercranked look

Ill try and explain

say you shot 4 frames per second, but wanted two frames per second then you just delete every other frame and the frames dont need realigning on the timeline 4 and 2 are 'in phase'

if however you wanted to convert 3FPS from 4 FPS 2/3 of the frames start at the wrong time

So far all my tests (even regular compressor on 'better') look sh1t anyway

S
 
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Good thinking, Sam!

I just checked in Premiere, stepping through 30p footage in both a 24p and 25p project.

Using frame blend (which is default), in the 25p project, every 5th frame is non-blended and whole (20% of all frames).

In the 24p project, every fourth frame is non-blended (25% of all frames).

So using your method means less frames will have to be interpolated, by whatever means chosen.
 
so you think what I think ?

24 should be faster to do and/or play back smoother than 25

so 24AT25 will be equally better than regular 25

S
 
Good point! Not only will there be less interpolated frames and thus less chance of weird artifacts, it will also be faster to render, assuming that retiming plugins really do spend less time on the frames that should be unchanged.

There's only one way to find out, and that's to do a test.

Are you game?
 
OK

(new) Thinking thus far

there are three factors..

Phase difference - time taken of frames being wrong

Frame quantity

Possible duration manipulation

I think, that 24p allows more regular phase allignment with a larger 'mis time'

25p has less regular phase allignment but smaller mistimes

so each has its downsides

which is better, im not sure at the moment

so for example a fast scene with no dialoge - best just 30/24 - perfect phase and framing - duration is 'wrong'

for other shots 24at25 might be better
and for others (slow shots) at straight 25 might be better


S
 
morgan_moore said:
24 may be a better fraction of 30 than 25
Click to expand...


How would 24 be 'better' than 25 (as a target division) ?

How are you emplying the word 'better' here ?

Would you be using a motion conversion technique that uses motion vectors (pixel motion) ?


morgan_moore said:
Meaning better 'phase allignment' at the exchange of a very slightly undercranked look
Click to expand...

How is 'phase alignment' better with 24fps - rather than 25fps.

Do you know how motion vectors work ?
 
Lets be clear here - im not spreading knowledge or arguing a specific theory - Im thinking aloud about how to do a retime in a manner that is least 'stressful' to the frames

24 is 'better' in phase with 30 because 1/4 of the frames are shot at the 'right time' compared to 1/5 for 25p

if you consider two sine waves - 24 and 30 line up more regularly than 25

"Do you know how motion vectors work ?" - no not intimately !

As I said my latest thinking is that while 24 'lines up better' when it is out of line it is out of line worse !

My thoughts on retimes are..

30-24 slomo - no stress/artifacts but time synch is well out - overcrank effect clearly visible
30-24-sped up to 25 - less stressful artifacts in 3/5 of - mild loss of timesynch by 4% undercrank (not noticed)
30-25 most stressful perfect timesynch but lots of artifacts in 4/5 of the frames

I might try a 30-27 with mild overcrank to 25 !

S
 
This is just theory,you must try it in practice , i tried 30p to 27 and then 24p but i dont like how it came out (still too smoth)also tried 30p to 22 and then 24p which i like most cause i dont see 30p smoothnes at any time.
Different editors give different results also blending or not blending will give different results.
Plus it depends on whats in the frame if its shot of moving object like a car then it will jump every now and then but if its some non linear movement then it should be ok even with simple frame dropping.

23.976 in films is speed up to 25 in tv but it was captured in 23.976 so it doesnt matter anyway cause 24-25 is not a big deal in difference.
 
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OK

Im seeing after many conversions !

25p done with compressor best (takes ages) is really no different from 24p compressor best

both handle adequately simple shots
both cause serious double image on fast shots

compressor CANNOT handle fades so do them afterwards

if I were trying to make a seirous production with the 5d I would probably go..

dialogue 30-25/4 in compressor

fast action go 30/24 overcranked

S
 
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