Variable Frame Rates

whachusay

whachusay

Active member
Is it possible to shoot with variable frame rates with the A1? I just saw the article by Barry and Jarred regarding variable frame rates on the HVX and I was shocked. From what I understand the A1 doesn't offer the variable frame rates like the HVX but is it possible to produce something similar in post? If not I might be asking an HVX to come live with me:):):)
 
Nope.
The HVX is the only sub 10k camera that shoots at variable framerates. And that's thanks to the P2 recording system. Tapes move at a fixed speed and can't be used to record variable framerates (in cams of this price). Because P2 is a memory card, you can write to it at any speed you want.

The next camera with variable framerates is the Varicam .. but that's a whole other league of camera.


Ok, to be picky, yes you can shoot 30P with many other cameras and then slwo it down to match a 24P project, or vice versa, but that's it. Not much creativty.

- Mikko
 
Actually, you can get a fair amount of frame rate looks with the XH cams. Shoot 24F with slow shutter speeds and different speed-ups in your NLE and you can approximate a number of undercrank looks.

It's possible to have 24, 25, 30, 50 and 60p. (the last two from 1080i deinterlace techniques that can look surprisingly good, especially converted to the 720 format)

It's not as comprehensive as the HVX under/overcrank but you can get good slow and fast motion effects if you're creative in post.
 
Elton's right back when this site was only about the dvx and Barry's book was famous, he had written a whole slew of ways to get different framerates from the dvx, not a ton but better than nothing. Things like 12,15,48 frames per second. I find it hilarious that so many people read and praised that book but now that the hvx is here they refuse to acknowledge that that stuff was ever possible.

The same frame rate mechanics in the dvx can be applied to any camera that can capture 60i, 30p and 24p.
 
You can try to simulate some effects. In the case of fast motion, you can get pretty close by messing with the shutter speed and speeding up in post. In the case of slow motion, you're just not going to be able to get the true silky smoothness that you'll see with true overcranking.
 
You can't easily get all the subtle incremental overcrank looks, (36, 40 46 fps, etc.) but I've achieved pretty much the exact look of 60p 2.5 slow mo with "silky smoothness" too. It's just temporal information, and 1080i has basically the same amount as 720 60p.
 
^
How? You record 60 fields per second in 1080i to make up 30 progressive frames. How is that the same amount of temporal information as 60 progressive frames?
 
Because of the resolution difference!

Both have the same data rate, the same compression, the same pixels per second (temproal resolution).
One has less bigger frames (that can be split in half into more smaller fields [and become frames]) the other has more smaller frames.

Intead of making the 1080.60i into 1080.30p and then throwing out pixels to make 720.30p, you can take the 1080.60i and use each filed individually. (1080/2).60p That 1080/2 gets you very close to 720. The result: almost 720.60p

- Mikko
 
1080/60i is really basically 1440x540x60. So you up-rez the 540 and down-rez the 1440 and you end up with 1280x720x60.

Barlow's shown some clips before. Looks pretty decent; too much stair-stepping for my taste but it's basically the same technique we used to use to get 60fps slow-mo from a DVX. The footage gets softer, but the motion information is there.
 
DavidBeier said:
^
How? You record 60 fields per second in 1080i to make up 30 progressive frames. How is that the same amount of temporal information as 60 progressive frames?
Click to expand...

60i is 60 half-frames per second. 60p is 60 full frames per second. Either way, the camera is taking 60 pictures per second, i.e., separating a second into 1/60-second intervals. It's the exact same amount of temporal information. Temporal info isn't related to spatial info.
 
Return the Canon A1

Return the Canon A1

Okay, folks! Today is the last day I have to return my Canon XH A1, which I purchased about 10 days ago. After seeing the slow motion videos from the HVX, I am strongly concidering using the money from the Canon to get the HVX. It just seems like 60 half frames vs. 60 full frames per second is quite a bit of data.

The fluid slow motion shots I saw from the HVX are amazing and are exactly what I am trying to achieve. Would this ever be fully possible using the A1? If the final answer is no then I am heading back to the store to return my Canon today.

Please let me know ASAP because this boils down to $4k.

Thanks!!
 
NO.

If that is important for you the HVX is a better slowmotion machine. BTW I see a lot of slowmotion video (showmotion) on this site, but in the normal world (documentary, film, drama ) its an effect that you use rarely.

No variable framerate on the A1, high resolution chips? Yes.
 
Good slowmotion from a Canon requires post work: http://www.dvxuser.com/V6/showthread.php?t=77259&page=20

The HVX is the only camera that really makes sense when slowmo is a must-have-use-it-all-the-time feature. It's hard to beat instant slowmo playback off a P2 card.

Strangely enough though....when you shoot 1080i with a fast shutter like 1/120 and then playback the footage and hit the "slow" button on the A1's remote, it gives you a very good approximation of the speed and effect of 2.5 slowmo.
 
Last edited:
With the HVX, can you shoot 1080p 60p? I thought there were only variable framerates in 720p mode, but is 60p not considered a variable framerate?

BTW Kosher, what kind of work do you do that needs slow motion so much? I can't see a situation where the HVX definitely beats out the A1. If you need slow-motion for shooting action (sports), then it doesn't make sense to use the P2 card workflow.

When I upload my 1080i footage from my A1 in ConnectHD, would I be getting close to 60p if I uploaded as 24p 720p? I accidently uploaded 60i footage as 24p, and got a smooth slowmo that had the same motion as Elton's uploaded footage.
 
1080 60i can be converted to 720 60P from the A1 very seemlessly. like everyone has been saying, and I'll say it one more time, it is the exact same amount of temporal information. Since you are starting with 1080 60i, you can "down sample" to 720 60P while not really losing any resolution whatsoever. The only resolution loss would come from the inherant softness from interlaced CCD's but that's a whole other story.
If you are looking to do variable frame slow motion not just 60P, go with the HVX, it's the only camera that can do that. If you are just looking for 60P slow motion (which is what most people shooting slow motion on this forum do anyways) both the A1 and HVX will give you good results.
 
Not the HVX

Not the HVX

I did more research and the footage I found, that I THOUGHT was the HVX, was actually a camera specifically made for slow-mo recording at 1000fps.

I don't need slow-mo very frequently but when I do need it, it better be good ;)

On another note, I have seen some amazing demo reels created with the HVX. I have yet to see a totally compelling reel, shot with the A1, and would love to see some. Again, I havn't seen many clips or shows shot with the A1 but I have seen lots from the HVX.

If anyone has a good link with indy or pro footage shot with the A1, let me know.

Thanks!
 
Kosher said:
I don't need slow-mo very frequently but when I do need it, it better be good ;)
Click to expand...

If that will be our situation, IMO you're better of renting a designated slomo cam for the few times you need it. On IBC I saw the weisscam from p+s technik, very impresseive 1000fps slomo up to 1280x1024... But there are even better and much more expensive solutions out there...

redfuse
 
Mikko, isn't 24f at a different compression ratio than 30f to make it 25 mbit/s? Couldn't it be possible to have all different types of of framerates using this method?
 
Some information in 25f is repeated so that overall it matches the data-rate of 30f or 60i (25mbps)

Theoretically, yes it is possible to repeat frames (or fields) to store any frame-rate under 30f or 60i, but the HVX is the only camera to offer other speeds than 24fps (in addition to 30fps and 60fps)

- Mikko
 
You must log in or register to reply here.
Back
Top