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EX1R Slwo and Quick Motion

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Kevin Patrick
EX1R Slwo and Quick Motion
on Oct 11, 2012 at 2:31:54 pm

If you set the camera to 720/24P you can enable S&Q Motion and set the frame rate to 60 fps.

The camera will record 60 fps (no audio) but the playback will be at 24 fps.

How is this different from setting the camera to 720/60P and conforming to 24 fps? Which I have done in the past.

I need to go test this myself, which I will. I was just wondering if anyone could tell me what, if anything the camera is doing differently in these two scenarios.

Is there some benefit to the overall video quality using S&Q, versus conforming in post?

I can see the drawback as not have any audio if you are using the S&Q feature.


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Craig Seeman
Re: EX1R Slwo and Quick Motion
on Oct 11, 2012 at 4:59:06 pm

There's a big difference in data rate of the recording.
That 35mbps (VBR) is more or less the playback rate.
720p60 is recorded to be played back at 35mbps so when slowed down it's actually playing back at about 14mbps.
720p24/60 is actually being recorded at around 87.5mbps so it's played back at about 35mbps.
As to whether you can see the difference it may depend on the subject matter and the shooting technique.
I'd guess if the shooting involved a gradient or leaves blowing in the wind you'd see the difference.

This brings up another often overlooked difference. Shoot at 720p24 vs 720p60 and both are 35mbps which do you think has more bits per pixel per frame? The data rate is the same per one second but with only 24 frames there's more data for each frame.



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Craig Seeman
Re: EX1R Slwo and Quick Motion
on Oct 11, 2012 at 5:04:42 pm

I'll venture down this slope a bit further.

That increased data rate shooting slow was one of the reasons why, in the early days, one couldn't shoot slow mo reliably on SDHC cards. The fail would happen after some seconds (exact time depended on the card) because you were "overrunning" the buffer. Note how that became more reliable with firmware update but the duration of stored data decreased with one of the firmware upgrades. I suspect Sony improved this by increasing the buffer in some form and the card is playing a role in that (thus reducing the amount of recording time).



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Kevin Patrick
Re: EX1R Slwo and Quick Motion
on Oct 11, 2012 at 5:21:30 pm

Craig,

You are jogging my memory on this issue.

So the S&Q mode is over cranking the data rate (87.5 mpbs) to record, but then playing back at the normal HQ data of 35 mbps. More data, better results.

I also just went back and looked at the brochure for the EX1R (since I didn't' see it in the manual). It states, "... images are recorded natively and at full resolution. The captured quality of slow-and fast-motion images is significantly higher than those created in the editing process."

I'm not sure how to convert your data rate explanation with Sony's. Natively? Full resolution? I thought the EXMOR sensor in this camera was full resolution? Or does the data get from the sensor get sampled/compressed? In the same Sony brochure, they refer to the sensor's as "effective pixel count of 1920 x 1080".

This sounds like there is more to this mode than just a higher recording data rate? Or am I reading too much into this?

Kevin


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Craig Seeman
Re: EX1R Slwo and Quick Motion
on Oct 11, 2012 at 5:46:22 pm

I'd assume it's just the data rate.

The sensor is being scanned the same rate at 720p24/60 and 720p60. It's still 60 frames worth of info at full sensor (I believe) but in slow motion there's more data being collected to "survive" the playback maintaining 35mbps.

Personally I'm curious about how the FS700 is doing it but it's certainly clear to all that there's a loss of resolution at over 240fps. Also note the record time changes, again pointing to the need to buffer and dump the data. In that case it's clear that at 960fps there's a lot less data being collected/saved from the sensor.

As more cameras move to higher frame rate slow mo recording, understanding how the manufacturers are doing this is important. I wish the information where more readily available.

What should be clear to all though is that generally shooting 720p60 and slowing down is NOT the same as shooting 60fps flagged to play back in another time base (24 or 30).



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