Slow-Mo in the camera with very low or high shutter speed
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AtticusLake
Well-known member
If you shoot 24p, then you get 24p. To get slo-mo, you need to shoot at a higher frame rate than your final movie; so if your movie is going to be 24p, shoot at 60p to have the movie be at 40% speed. On the FS100 you can use the S&Q mode for this, but you may as well just shoot 60p and conform it in your editor; that way you'll capture sound as well.
The same; if you use too fast a shutter you will lose the motion blur, and get a jerky image. I would suggest doing what you would normally do in terms of having the shutter speed be 1-2 times the frame rate. So if you shoot 60p, try to keep the shutter around 1/60 - 1/120. That'll give you smooth results. If you actually want it to look like it's been slowed down, for effect (perfectly valid, if that's what you want), then a faster shutter speed could be good.
The same applies the other way round; when shooting timelapses at 1FPS, I use a shutter speed of 1 sec to 1/2 sec. That creates a milky-smooth timelapse.
So this is more of a curiosity question for me because shooting in 60p would make much more sense so I can crank later (and maybe even keep the footage the way it is), but in S&Q mode...will it really still be jerky if I shoot with a high shutter?
I should just do a test, but that's interesting...
I should just do a test, but that's interesting...
High shutter speed won't look jerky in 60p conformed to 24p, or 24p in S&Q mode. Also if you have any motion blur, the slowmo effect won't be as good. Remember that high speed camera shoots at very high framerate and shutter speed. You want to simulate that look even though the framerate isn't quite up there. For some subjects (i.e. water), higher the shutter the better. So don't be afraid to go over 1/120.
Also S&Q mode will give you a higher bitrate -- that's main reason shooting in S&Q rather than 60p.
Also S&Q mode will give you a higher bitrate -- that's main reason shooting in S&Q rather than 60p.
This is why I thought it would make sense in the S&Q mode to shoot at a higher shutter..I was thinking it would be better for what's going on inside the camera and that it wouldn't have the same jerky, robotic motion like you normally would get from just regular shooting (not any slow motion mode)...
MattDavis
Well-known member
One of the things I noticed with my tests is that if you wish to do slomo in post (e.g. twixtor, the Foundry's Kronos), a little bit of motion blur was good as it helped the inter-frame morphing tools hide a multitude of sins. If you shot with a high shutter speed, things rapidly got bent out of shape. It sort of bucks the trend, but I'm simply reporting my findings.
True. If the subject is moving fast enough where the camera can't capture enough frames, the motion blur will help bridge the gap in between frames. Otherwise, twixtor wouldn't have enough frames to work with and start warping the image.
It's funny you mentioned that because I will be using Twixtor for next project. I spoke with one of the developers a few weeks ago about the software and he guaranteed that Twixtor works much better with less motion blur (aka using a higher shutter)...I did a test with a 10k shutter (had to pump up the gain a bit) and it worked very nicely...no morphing, nice pixel calculations...I know that using the S&Q mode is a separate issue, but just saying..
I'm grateful if we can clarify this -- because it's a big deal on this end.
I was under the impression that the highest FS100 bitrate was 28 Mbps in the 1080/60p mode.
Am I wrong?
You're correct that SP mode (1080/60p) records in higher bitrate at 28Mbps vs. 24Mbps (FX mode). Keep in mind that 28Mbps is VBR (Variable Bit Rate) -- it's not a constant bitrate but indicates it peaks at 28Mbps.
The keep difference between SP mode 60fps vs S&Q 60fps is that S&Q is overcranked 60fps, which means S&Q mode will capture a lot more data at any given time period. I won't layout all the math here but if you simple record the camera in both modes for exactly same time and same subject, the file from the S&Q mode will be approximately 3 time bigger (more data).
Also note that as mentioned in the manual the S&Q mode requires a class 10 SD card while non-SQ modes only needs class 4.
cheezweezl
Veteran
1080p/60 = 28mbps
1080p/24 overcranked to 60fps = 60mbps
When using S&Q, it maintains your native bitrate. Speed up your framerate and bit rate goes with it. S&Q is much better quality.
Regarding the shutter issue, I'm on the other side of the fence. 1/60 shutter at 60fps is what you should use to make your slow motion footage match your normal 1/48 footage as best as possible. Using a typical 180deg. shutter when overcranking results in choppier footage. It does have a certain look but to me it looks a little strobe-ish.
1080p/24 overcranked to 60fps = 60mbps
When using S&Q, it maintains your native bitrate. Speed up your framerate and bit rate goes with it. S&Q is much better quality.
Regarding the shutter issue, I'm on the other side of the fence. 1/60 shutter at 60fps is what you should use to make your slow motion footage match your normal 1/48 footage as best as possible. Using a typical 180deg. shutter when overcranking results in choppier footage. It does have a certain look but to me it looks a little strobe-ish.
eheath
Well-known member
i dunno about that.... i think the overcrank is higher quality because its not a VBR. if im not mistaken, bit rate its constant regardless of the frame rate (24p is 24 and 60p is 28)
SergeSmArt
Well-known member
Try to trasfer your files into Sony "Content Management Utility" and check your regular 24p files and 60P PS files .. and you will see the ACTUAL bitrate..
All my 24P files are 21 Mbps, instead of 24... and 60P PS files - only 25Mbps, insted of 28 .. so ..? .
VBR should still have more bitrate @ 28Mbps vs 24mbps constant bitrate since VBR shouldn't drop below 24Mbps. The real reason for S&Q having much better quality is because it's overcranked.
To expand on what cheezweezl wrote:
If you shoot for 1 second on both modes you get something like this:
60p = 28Mmps max
Overcranked @ 60fps = 24Mbps x 2.5 (the difference between 24fps and 60fps) = 60mbps
So you're looking at 60Mbps vs 28Mbps in 1 second of capture. This number should be reflected in the file size as well. When you overcrank the framerate, the conforming occurs in real-time in camera so you're capturing that much more data in the same time period.
eheath
Well-known member
this doesn't make any sense to me. one second of 60p stretched to 2.5 seconds wouldnt the bit rate go down by your calculation? you're taking one second of 28mbps and then cutting that clip into 2.5 seconds, wouldn't that stretch out the info over the 2.5 seconds making the bit rate lower? I just dont understand how you get overcranked 60p to be 60mbps. You're making me want to shot the same amount of time in each and compare the file sizes, im so curious now ha
cheezweezl
Veteran
for an apples to apples comparison, lets say 1080/60 is 24mbps rather than 28. ok if you shoot 1080/60 and then slow it down to 24fps, that means your original 24mbps worth of data just got stretched over 2.5x the time or just got reduced to 40% of it's original data rate. so shooting that way gives you the same data as if the camera recorded at 9.6mbps.
by overcranking, the bit rate increases with the framerate, therefore maintaining your target bitrate when the footage is played back in it's intended framerate (slow motion)
or a simpler way to understand it is that 24mb spread across 24 frames = 1mb per frame. 24mb spread across 60 frames = .4mb per frame. much less info.
so understanding this, the original statement (just record in 60p and slow it down so you can have audio. it's just as good) is false, but the opposite is true. meaning, if your project is at 1080p/60 and sound isn't important or is being recorded separately, you could shoot everything at 24fps and overcrank to 60fps to get the highest quality possible. of course you would have to conform the clips in post but it could be done quite easily.