One Summer Evening with the FS700

[Alister Chapman]

Not quite sure how Den managed that and I'm not sure he is too, as the Samurai on paper can't do 1920x1080 50p or 60p.

I'm still looking in to this. I'll have access to a FS700 on Thursday and I'm taking my Gemini which can do 1080p60 to test it out.

[Lonnie Bell]

Look forward to your results Alister - Happy Shooting!
Lonnie

[Chris Medico]

Keep us posted Alister. I would enjoy getting to try one out myself.

[Peter Corbett]

Originally Posted by Alister Chapman

My suspicion is that the camera is storing the 240fps video in an internal memory buffer and then reads out that memory at 60fps, writing a 60fps AVCHD file to the SD card that is then flagged to playback at 24 or 30fps.

I did a Weisscam 1000fps shoot yesterday and this is the exact same principal that camera works under. It internally records to a RAM buffer then prints out to HD-SDI in real time, so it takes a while until you can take another shot. I have to say filming rugby players at 1000fps under a bevy of 18K HMI's looked absolutely amazing.

[Alister Chapman]

I can confirm that you can read the 50/60 fps buffer stream vis 3G Sdi to an external recorder. I was able to test it today recording uncompressed to a Convergent Deign Gemini. So, 240fps uncompressed is possible. Very cool!

[Lonnie Bell]

Thanks for the follow up, Alister!

Will a single link HD-SDI work at the 240fps or does it need to be 3G?
(the Samurai specs per their website, they list the input as HD/SD and the output as 3G/HD/SD. And based on Den Lennie's report - I'm a little confused...)

Thanks for shedding info and light!
Lonnie

[Alister Chapman]

The FS700 writes slow mo from the memory buffer to AVCHD and the SD card at either 50 or 60 fps depending on which country zone the camera is set to. The camera output can be set in the menu to either 25/30p or 50/60p, if set to 50/60p the output is 3G. In either case the buffering happens at 50/60p. So, if the output is set to 25/30p you only get every other frame on the output Sdi at 1.5G. The end result of this is that if you shoot at 200 fps with the camera output at 25p you would end up with an external recording the equivalent of 100 fps with a 180 degree shutter. Still very useful and a nice option. But to get the full benefit of external recording you need to set the FS700 to output 50/60p over 3G SDi and then you must use an external recorder that has 3G SDi and can record at 1080 50/60p which the samurai can not do.

[Lonnie Bell]

Thanks for the succinct answer and always a pleasure to read and watch your craft, Alister!
Lonnie

[Walter Brokx]

Originally Posted by Alister Chapman

The FS700 writes slow mo from the memory buffer to AVCHD and the SD card at either 50 or 60 fps depending on which country zone the camera is set to. The camera output can be set in the menu to either 25/30p or 50/60p, if set to 50/60p the output is 3G. In either case the buffering happens at 50/60p. So, if the output is set to 25/30p you only get every other frame on the output Sdi at 1.5G. The end result of this is that if you shoot at 200 fps with the camera output at 25p you would end up with an external recording the equivalent of 100 fps with a 180 degree shutter. Still very useful and a nice option. But to get the full benefit of external recording you need to set the FS700 to output 50/60p over 3G SDi and then you must use an external recorder that has 3G SDi and can record at 1080 50/60p which the samurai can not do.

This is very, very interesting to know!

[Chris Joy]

God that 240fps is sweet, I thought the S&Q 60p on the FS100 was the beez-neez. This already has me thinking upgrade from my FS100 that I've had for a scant 2 weeks now. Nice...

[Cees van Kempen]

Originally Posted by Alister Chapman

The FS700 writes slow mo from the memory buffer to AVCHD and the SD card at either 50 or 60 fps depending on which country zone the camera is set to. The camera output can be set in the menu to either 25/30p or 50/60p, if set to 50/60p the output is 3G. In either case the buffering happens at 50/60p. So, if the output is set to 25/30p you only get every other frame on the output Sdi at 1.5G. The end result of this is that if you shoot at 200 fps with the camera output at 25p you would end up with an external recording the equivalent of 100 fps with a 180 degree shutter. Still very useful and a nice option. But to get the full benefit of external recording you need to set the FS700 to output 50/60p over 3G SDi and then you must use an external recorder that has 3G SDi and can record at 1080 50/60p which the samurai can not do.

So if I understand well I can make a burst shoot of 240 fps (ntsc setting), record it as I-frame with my nanoflash set at 1080p30, thus taking 120 fps of the initial 240. With Cinematools flag it as 25p and import it in a 25p timeline. The end result is 120fps brought down to 25p, so almost 5 times slomo with the nanoflash. Correct?

[Alister Chapman]

Yes, that is correct. It would be the equivalent of 120fps with a 180 degree shutter or 1/240 shutter.

[Noah Yuan-Vogel]

One thing probably worth considering with overcrank 60fps, 120fps, 240fps footage recorded to AVCHD is that AVCHD has a significant temporal compression component which likely gets more efficient as motion gets slowed down. As you increase framerates, the similarities between frames almost always become significantly greater, which should allow the efficiency of long-GOP AVCHD to increase substantially. I'd be interested in testing this, but my understanding is that GOP codecs do exceedingly well at recording a bunch of very similar frames.

Then again some of this effect may be lessened slightly given the lack of motion blur at such frame rates.

[Alister Chapman]

Yes, long GOP codecs become more effective at higher frame rates due to the reduced temporal differences between frames. The FS700 takes full advantage of this. At up to 30fps the bit rate is 24Mb/s, when you go to S&Q mode the bit rate increases to 28Mb/s for 60fps, so only a 4Mb/s bit rate increase but double the number of frames.

[Noah Yuan-Vogel]

isn't the 28Mbps AVCHD mode only for 1080p60 recorded footage? That is how it works on my FS100, if I want to record S&Q it is always records the 60fps footage into 24fps FX mode (24MBps)