18 fps

[PITIRRE]

Can you make a film that run at 18fps transfer it to DV with the intent to showing on TV? There is not much sync sound very little

[Andreas Wideroe]

Sure you can, but if you make pulldown to Ie. 25fps you'll loose some sharpness, actually quite a lot. If you speed it up to 25fps it will look sharp, but people will move like they did in the 20s!

[tlatosmd]

What sharpness do you mean Andreas? Sharpness in movement resolution? Other than that, I've made it to get telecined S8 K40 at 18fps look like 16mm by sharping in post. The file should be on your ftp as a web-reduced AVI with a title of 'Prague' something.

[Andreas Wideroe]

If you want to make 25 frames from a source that is 18fps you would either need to copy some frames that makes the image look jumpy. What most scanners do is to create new interpolated frames that consist of two different frames. This will make the film look slightly blurred when played back.

[tlatosmd]

If you want to make 25 frames from a source that is 18fps you would either need to copy some frames that makes the image look jumpy. What most scanners do is to create new interpolated frames that consist of two different frames. This will make the film look slightly blurred when played back.

You mean an interlacing pullup like NTSC? I prefer frames, and so far non-interlaced footage hasn't looked jumpy to me...probably because I got interlaced footage and then deinterlaced it.

[René]

I always convert my PAL dv-footage to 24p using two very useful After Effects Plugins: FieldsKit and Twixtor. The first one is an intelligent deinterlacer and the second one slowsdown/speedsup footage and simulates the correct motion blur. It morphs between frames, instead of just combining them. It should work for this purpose. You can download trial versions of each plugin to see if it fits your needs. Also, I'd be happy to process some footage for you to test it.

[ccortez]

You have asked this same question so many times here on this forum that you could have run tests at 18 and 24 fps many times over and found out for yourself.

If you want to reintroduce or clarify the question, at least go back to one of the original threads and bring it back to life. That way, when future folks are searching for answers, they won't find a million threads with the same half-started discussion.

Rather, they'll just find one reeeeaaaalllyyy long thread... with a half-started discussion. ;)

[Uppsala BildTeknik]

You people are de-interlacing???
Why not just scan it with a "progressive pulldown", or scan it in full speed (25 fps for PAL) and then perform the pulldown yourselves in your NLE, and make it progressive??

[tlatosmd]

You people are de-interlacing???
Why not just scan it with a "progressive pulldown", or scan it in full speed (25 fps for PAL) and then perform the pulldown yourselves in your NLE, and make it progressive??

Because it might get jumpy (not as in bad registration), just like 29.97fps NTSC cramped into a 25fps PAL file without motion blur (or, as in my case, deinterlacing in post), it looks like about 5fps.

(Anyway, isn't a 'pulldown' when you decrease framerate, and 'pullup' when you increase it? Only way it etymologically or syntactically could make sense to me.)

As for Twixtor, I guess that prog must've been invented by stoners.

[Uppsala BildTeknik]

But what is the difference between a interlaced footage that has progressive pulldown, and a interlaced footage with interlaced pulldown that is deinterlaced?

As far as I can understand it the only difference would be that the deinterlaced footage has much lower resolution. :?

[tlatosmd]

As far as I can understand it the only difference would be that the deinterlaced footage has much lower resolution. :?

As much as I know, that's a common misconception, or rather, a misunderstanding. What is reduced is not pixel resolution but temporal resolution (25 or less frames instead of 50 fields). Though I think it's actually not half the temporal resolution as 50/2 = 25 would suggest but actually three quarters as much as deinterlacing blends in the field information at a 50/50 proportion into the resulting frame, not 50/0.

Pixel resolution remains identical and interlacing artifacts (looking similar to low pixel resolution artifacts) are even reduced from blending fields that contain half the pixel resolution into a frame with full pixel resolution, so you could even say it doubles pixel resolution while reducing temporal resolution.

[Uppsala BildTeknik]

OK, I maybe can understand how it would make movements a little bit smoother then, but the difference from progressive puilldown shouldn´t be that big.

I knew the "pixel resolution" is the same after deinterlacing, but the "image resolution" is lowered quite a bit.

Have you seen film with progressive pulldown or was it just interlaced footage that you deinterlaced and came to the conclusion that it is the way to go?

I´d say the next time you are going to get your films scanned: scan them with 25 fps and then play with pulldown in your NLE, it won´t look that bad and jerky with progressive pulldown, at least not to me... Then also try to deinterlace the same footage and compare the difference in full screen, I think that the deinterlaced will loose...

[Uppsala BildTeknik]

Here´s how I look at the pulldown and deinterlaceing thingy, AA represent the both interlace fields from image A, BB the interlace fields from image B and so on... Lets concentrate on image B for pulldown.

With Progressive pulldown: AA BB BB CC DD (and so on)
With interlaced pulldown: AA BB BC CC DD (and so on)
With deinterlaced pulldown: A B B C D (and so on)

The BC image will look blurred and "bad" on a computer, no good for computer-use.

The BB is a repeated frame and will look perfectly good, but the motion seems a bit jerky because of the repeated frame.

The deinterlaced B is still a repeated frame and shouldn´t give much better motion than the progressive pulldown, however we have removed a lot of image information and the result can only be less sharp.

However if the deinterlacing somehow mixes the BC image fields I guess it will look a little bit smoother than the progressive pulldown, but can the difference really be so big that it is worth loosing image quality over it?

[tlatosmd]

Here´s how I look at the pulldown and deinterlaceing thingy, AA represent the both interlace fields from image A, BB the interlace fields from image B and so on... Lets concentrate on image B for pulldown.

With Progressive pulldown: AA BB BB CC DD (and so on)
With interlaced pulldown: AA BB BC CC DD (and so on)
With deinterlaced pulldown: A B B C D (and so on)

If that progressive pulldown is what I think it is, it gives you a stunningly smooth slomo at a 2:1 ratio.

The BC image will look blurred and "bad" on a computer, no good for computer-use.

[...]

However if the deinterlacing somehow mixes the BC image fields I guess it will look a little bit smoother than the progressive pulldown, but can the difference really be so big that it is worth loosing image quality over it?

What you call 'blur' from deinterlacing is nothing but old-fashioned motion blur identical to a lower shutter speed as a video cam recording 50 fiels per second has a higher shutter speed (thus giving less 'blurred' motions) than a progressive video camera at 25fps (frames) or a movie camera running at 24fps. That's (one of the) main reason(s) why deinterlaced and progressive footage look so different from each other and why progressive footage has so much smoother (aka 'blurred') motions.

[Uppsala BildTeknik]

Well the pulldown is not exactly those numbers of frames repeated, I just took 4 frames from the middle of a pulldown as an example.

But on a TV the interlaced alternative is even smoother in motion, because the TV shows field A, then A, then B, then B, then B, then C, then C, then C, then D, then D... and so on

Instead of the progressive A, then A, then B, then B, then B, then B, then C, then C, then D, then D... and so on

You see the interlaced is a tiny bit smoother on interlaced monitors (like TVs).


What I call "blur" from deinterlacing is the blurry images that must be the result of making a slight mix of 2 different interlace fields instead of showing them in their original shape.

Progressive footage (as in shot with 24 or 25 fps) are of course the best and sharpest alternative, with a bit shorter shutter speed too.

But if you shoot it at 18 fps and then transfer it with a "progressive pulldown" the images will still be perfectly sharp on computers (no mixed interlace fields that are displayed at the same time) with the same shutter speed as 18 fps gives (of course) and the motion will be at least almost as smooth as with your deinterlaced footage. I´m not talking about motion as in how the images look on the film itself (shutter speeds) but rather how the images are repeated in the final video-file. How often they are repeated and how often a new frame from the filmreel is displayed.

I mean, deinterlacing of course must lower the image quality quite a bit because you are throwing away a big part of the image frame and using the rest of the image to "fill in" the holes that the removal of one of the interlace fields has left behind.

Look at it as if you would slice your 8mm footage to 40 very thin slices. Now take half of those thin strips and throw them away, and glue the remaining thin strips to eachother and you have your "deinterlaced 8mm reel". Oh, and you need to do this to every frame on the reel, so it will take you the rest of the week! :lol: