Data Rates ProRes 422 S-Log

[xyzowen]

Hello all,

This is my first post on the forum, so forgive me if this is a stupid question but:

Last week shot a music video on the F3 in Slog, recording ProRes 422 HQ to a Ki Pro Mini.
If recording in ProRes 422 HQ gives you a data rate of 220mb/s, then why when I drag
a clip into FCP7 and look in the data rate column, for almost all my clips it ranges between
13-14MB/sec. Is this not the same thing, or am I looking in the wrong place?

I thought this was wrong so looked instead for something that looked much nearer 220mb/s
in the file info in Finder. I found that most of the files had a total bit rate of between
115,000 to 130,000. But surely that's wrong if I was recording in HQ? Or is 220mb/s just a
target/mythical rate?

I have a feeling that I am being a complete noob when it comes to bits & bytes, and am keen for someone
out there to help explain it to me.

I also noticed a bit of noise, some aliasing and highlight oversaturation on some shots, despite shooting at
iso1600, shooting at an optimum stop and ensuring a healthy level of info on the waveform.
Any thoughts/tips/advice on that would be great!

Thanks a load in advance!

[alisterchapman]

The noise is because you used 1600 ISO, S-log is designed to only be used at 800 ISO, using 1600 reduces your dynamic range, shifts mid grey and will increase noise. S-Log exposure is very different to normal gamma exposure. Middle grey at 800 ISO should be 38% some 1.5 stops lower than REC-709. White will only be 68% so the image when correctly exposed will be much darker than conventional gamma.

If there is little information in the picture then the bit rate will be lower.

[xyzowen]

Hi Alister,

Thanks a lot for your help, very informative.
I'll shoot 800 on my next slog project in feb and take into account those middle grey & white
readings.

I think I'll try & light more off the mon this time. I lit according to waveform (approaching
it like a normal gamma) and probably a bit too religiously, which obviously alongside with
pushing my ISO will have degraded my image. Although considering those readings im
surprised my whites didn't overexpose too much considering those readings.

Thats what happens with minimal prep/research i guess, thankfully its a Uni project and I
can use it as a learning tool

Thanks again