PJ McConnell
Member
Quick question for future reference
which would create a cleaner slowed down clip. 1080 shooting at 30p or 1080 shooting at 60i? I was always taught to stay away from interlaced, but does the higher number of frames per second make slowed down clips cleaner? Or does the interlacing interfere too much?
CraftersOfLight
Member
I found this article very informative on describing the differences in frame rates. It might afford you some answers.
http://ddisoftware.com/tech/articles/march-2009-video-frame-rates-(24p-25p-30p-60i)/
Rob Grauert
Post Production Host
Who told you to stay away from interlaced? There's nothing wrong with interlaced footage. It all depends on what you're doing.
30p and 60i are both 30fps.
What software are you going to be working with?
EarlC
Moderator
Rob, his primary question and concern is whether progressive, or interlaced footage would result in cleaner slow motion. IMHO, cleaner slow motion would be derived from progressive, but as Rob said, it does depend on what you're working with, your software and sometimes even perhaps the platform as well as how the originating source material from the camcorder or unit used handled the footage being videotaped and recorded.
Rob Grauert
Post Production Host
Yea, but he said, "I was always taught to stay away from interlaced, but does the higher number of frames per second make slowed down clips cleaner," indicating that someone told him to generally stay away from interlaced, but he's wondering if interlace is a better option in this instance.
His actually question may be about slow mo, but that doesn't mean it shouldn't be made clear to him that there isn't anything wrong with interlaced footage
Hogwild
Member
PJ,
Progressive footage should result in cleaner slow motion since it's captured as complete frames at your specified rate of 30p - so 30 complete frames per second.
Interlaced footage is also 30 frames per second, but it's split into separate odd and even fields yielding 60 fields per second, rather than complete frames. When played back, the fields are interleaved very quickly and gives the illusion of complete frames. If you take a still image from interlaced video with a lot of motion, you will see some a combing or a stepped pattern. If you slow down the interlaced footage playback rate, you will likely see the same, maybe as detail blurring.
Either way, both formats have their place depending on the project's intentions and a flat out statement to "stay away from interlaced" isn't an all encompassing solution to everything video.
What camera are you using and what are it's frame rate capabilities? If you want truly dramatic slow motion, use a camera that shoots 60p and slow down the footage. That will be spectactular.
grinner
Member
Progressive is cleaner the more you slow it down... simply less strobe. Much of the time it has to do with the action to see the difference, even down below 10 fps. What you use to slow it down matters bigtime. After Effects handles it very well as does Avid's motion blending and fluid renders. Frame renders handle aliasing beter at the cost of stobing galore and field renders handle motion but can tear an image up bigtime.
roblewis56
Member
leaving the question "When is 60i preferred over 30p?
Rob Grauert
Post Production Host
60i will give you a crisper image if you're shooting fast action, such as sports, since you have 60 fields. But I admit that logic makes you wonder why ESPN prefers 720p.
Also, 24PsF is sort of like interlaced footage. It was created to reduce the necessary bandwidth for 1080p24
CraftersOfLight
Member
I just tried both last summer.
Last summer I was experimenting with my HMC40 in 1080 60i and 1080 30p. Unscientific at best I was trying things with it to see what was best for my application. I had the camera set up and looking out the side window of my truck. I then recorded driving around the block, a distance if about 3/4 mile with speeds up to 40 mph in some sections (on a boulevard). The only setting I changed were the two rates. What I noticed direct playback to the TV was that the 30p looked sharper but the 60i looked smoother. When I slowed the frames down in my editing software I noticed that with the 60i anything with a vertical element started to show stair-stepping on that edge. Signs in general looked to be slightly out of focus on those verticals but had good sharp edges on the horizontals. 30p showed sharp edges all around.
And yes, being a cmos sensor, vertical lines started to lean into the travel direction, becoming mildly noticeable at around 20 mph. But still at 30p they were sharp and 60i had slight stair-stepping.
Eventvideoguy
Member
I wish that when watching or working with 60i footage on my NLE, that I could see the individual interlaced frames and not just the combined picture.
roblewis56
Member
We should not confuse the frame rate used in recording, such as 60i or 30p with that used in displaying, such as 700p on a TV. In the latter the 700 refers to the number of horizontal lines of pixels written progressively on the TV screen.
When you record at 60i you get two half interlaced frames, essentially two overlapping images shifted in time by any movement that took place during the time of half a frame, about 1/60th sec. When you shoot at 30p you get one image. I suggest you check this for yourself by shooting some moving subject at both 60i and 30p and compare the results on you computer. Look at individual frames to show the difference most clearly.
I did this using a passing train as subject. I have shown this before, but repeat here below.
| Get the Flash Video |
My conclusion is that 30p is always better than 60i if there is any motion. And if there is no motion there is no video.
To smooth out motion use an intermediate shutter speed rather that a very fast speed. I show this below.
| Get the Flash Video |
Robert
Eventvideoguy
Member
Was the second video using 30p or 60i?
roblewis56
Member
30p
PJ McConnell
Member
Thanks for the replies everybody, for now this was just for future reference and does not involve anything I am doing currently. I will remember your advice (I hope)!
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