fps choice 25p vs 30p (PAL) for run and gun shooting

kostas

kostas

Well-known member
I haven't seen this argument discussed as such, so posting a new thread.
I have always shot everything in 25p with 50 shutter speed (PAL) except when having in mind slow motion and depending on camera (50p, 100 shutter). This in order to have a look that is not the 100Hz TV, which I find totally artificial.
Recently, I had to shoot a small corporate clip of a lounge bar and with my partner we have been arguing a lot on the framerate.
He sustains that for this kind of run and gun shooting where cameras are always in motion, it is much better suited to shoot 30fps for smoother motion and then conform to 25p with Premiere if you need that format (film, dvd, TV), rather than shoot directly in 25fps. He says that shooting 25p directly is more suited to a movie setup where all the cameras are rather firm and the subjects are moving.
I have always thought that it is better to shoot in your desired framerate rather than having software conversion in post.
So we have a bit of a disagreement here.
Anyway in that particular case, we have shot 30p then conformed to 25p, since our clip has been transferred to film and projected on a big screen.
And there was no sound in real time.

I have understood that Premiere can merge several clips shot under different framerates quite succesfully, and maybe it is no big deal for the average viewer, but I would like to have my mind settled and understand why I am doing what I am doing in the future.

So is it true that 30p conformed to 25p (when needed) gives smoother motion compared to shooting 25p when it comes to events and/or other run and gun shooting with moving cameras?
 
1.) Frame to frame (dropping 30fps on 25fps timeline) going from 30fps to 25fps will result in 30% longer clips, or appear to be slightly slowed down. This is noticeable to the viewer as it will look like slow-motion effect.

2.) To keep clip time/length the same however you will need to do reverse telecine process to go from 30fps to 24fps, then you can drop your 24fps clips to your 25fps timeline and only effect is 4% shorter overall clip length. This is not noticeable to the viewer at all, and incase there was audio you need sync'd you can use any good audio program to shorten the audio file by 4% and keep pitch the same and match the "new" length of our clips on 25fps timeline.

I have done format conversions since early 2000 when I shot on PAL cameras here in North America to get 24p images long before it was available on pro-sumer camcorders.
 
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Thank you for your reply. What I understand from the reverse telecine process is that it is rather tedious, especially if you have to work with sound.
But If I shoot the same scene (where my camera may move for instance on a steadicam) a) in 25p, and b) in 30p and reverse telecine 30p to 24p and then conform to 25p will there be a difference in smoothness of motion between the two?
 
there is never any impact to sound if conversion is done to frame and the overall length of time of the clip is not changed.

ie. 60i to 24fps was a common effect used to simulate the look of film. While frames were interpolated, mixed and blended using different methods the overall clip length was never changed, and therefore the sound was not impacted. ie. going from 50i to 25p does not change clip length.

So going from 30fps to 24fps will not impact your sound if you use a process that does frame rate conversion. As I mentioned though once you put 24p footage on a 25p timeline the clip length now changes and is 4% shorter because there is one less frame for every second of footage. Your sound clip from before if you drop it on your timeline (if it was recorded separately say...) is 4% longer than your clip. You need to shorten it by 4% in an audio program (some NLE software will do it too now, just enter 96% as your new clip length on your audio file).

As for difference in smoothness, there will be no difference in smoothness from 24p to 25p or 25p to 24p.
 
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Kostas, I see the dilemma you two are having. On one hand your partner is correct insofar as at 25fps you can get some judder in the image. How much better is it at 30fps however? Not a great deal IMO and with the hassle of what you're doing / now going through, it's not something I would prescribe to in future.
 
Thanks for the replies.
What my partner does is:
shoot at 30fps, edit in premiere, export from premiere to 25fps with the frame blending option.
He claims that it is smoother than shooting in 25p and no hassle with sound or lengthy reverse telecine.
That way if the output is bluray, then 30fps is fine, if it has to be DVD or film then exporting from premiere to the desired framerates takes care of the rest.
That is what he says. I don't know if there is a pitfall in this reasoning.
 
Frame blending lowers quality, that's the only pitfall but if he really likes a smoother image from 30p and he has tested his methods and likes them, then all power to him. I do like the look of 30p myself but never shoot with it.
 
You shouldn't even be thinking about 30p if you're in PAL and plan to stay that way. It will not make a good conversion, and there's no way to cheat it -- it makes a lousy conversion to 24p as well, and if you try that with the intent of then converting the 24p to 25p, it'll be even worse than just trying to convert 30p to 25p or 50i.

Also, if you convert any frame rate to any other frame rate, even if done very successfully, the video will take on the characteristics of the new frame rate as though it had been shot at that frame rate the whole time. (if it didn't, there would never have been a reason to convert 60i to 24p.) So, if you shoot at a faster frame rate because there's less motion judder, converting to the slower frame rate will introduce the judder to the video. The judder is all about pictures displayed per second, and if you're only displaying 25 pictures per second, it doesn't matter if the original footage was 30.

If what you want is ultimately 25p, then the better move by far is just learn to shoot with 25p's characteristics and move the camera accordingly.
 
The dilemma comes from the fact that some clients want to have their clip delivered in Bluray and as far as I know Bluray doesn't support 25p. So it has to be either 24 or 30, whereas for others DVD may be fine, so it has to be 25p. Some may want both Bluray and DVD. This means that most probably a conversion has to be done.
Apparently, frame blending may be the option that keeps things smoother while converting 30p to 25p, but I understand now that it may lead to lower quality. How much lower? Has to be verified.
 
Blu-ray supports 50i, though. You can export the 25p in a 50i stream for Blu-ray. Each 25p frame will make up a field pair, so no one should be able to tell the difference.

Frame blending will create its own artifacts, like ghosting around moving images, and there will be jumpiness which wasn't there before.
 
Shoot 24p. It goes to 25 and 30 easiest.

Audio is a sinch if you follow the instructions I posted above. Anyone who disagrees hasn't tried it. PM me if you get stuck.
 
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Ooops sorry for lack of clarity (I was on blackberry).

I'm advising if you "had" to choose between 24p and 25p for distribution to 24p, 25p or 30p then I'm saying chose 24p not 25p - as 25p to 30p is less of a frame-mix-mess than 24p to 30p and also 24p will go to 25p nicely. (with the 4% speed sound adjustment)

But to answer the previous post as to "how much quality" is suffered. Quality is extremely subject and I hate when people quote numbers, percentages, and other numerical facts when in the end sometimes compromise is necessary to get what you want and the end result ain't so bad and can't be measured.

I was converting 50i to 24p in the good old SD days and back then had pixel aspect ratio to worry about let alone frame rate. These days, if you're shooting HD or even higher resolutions, I don't think the "quality" will suffer all that much or be noticable to users if that's what you're asking.

The best thing for you to do is test it yourself by shooting a resolution chart along with other shots comprised of high detail, and be sure to test both STATIC and MOVING shots. In my experience, frame-blending and interpolation is only "really" happening when there is motion in the clip, which in turn is really the only place that "quality" will be altered. I got pixelation on edges sometimes, but depending on the scene or clip I would try different modes that were available to me at the time.

Test it and post your results and conclusions.
 
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