F3: S-Log oversaturates green channel

D

dstruning

Member
I recently did some tests with the Sony F3 and recorded 1080 25p with S-Log onto a SD card using the SXS adapter. I recognized some poor oversaturation in the green channel (check the video below). I already had the same issue with the Sony FS7, but once I turned off the matrix, everything looked great! So maybe it's something similar here? Can anybody explain this?

https://vimeo.com/134506195
PW: green
 
SLOG doesn't really work properly in 8-bit 4:2:0 35mbps XDCAM anyway, the recording format doesn't have the bit depth or tonality to properly capture SLOG. So I'd expect banding and other artifacts and issues to show up pretty easily.

Are you using 'proper' SLOG? Or just the picture profile version? If the picture profile version you still have to turn of matrix, sharpening etc. to get a clean SLOG recording.
 
Grug said:
SLOG doesn't really work properly in 8-bit 4:2:0 35mbps XDCAM anyway, the recording format doesn't have the bit depth or tonality to properly capture SLOG. So I'd expect banding and other artifacts and issues to show up pretty easily. ...
Click to expand...
Correct, you will loose information when recording in 8-bit 4:2:0. Just wanted to test it and it's not that bad...

Grug said:
... Are you using 'proper' SLOG? Or just the picture profile version? If the picture profile version you still have to turn of matrix, sharpening etc. to get a clean SLOG recording.
Click to expand...
I finally understand that all the settings are within the PP menu... I turned off matrix and it worked. No more oversaturated green, thanks!

However, I still don't understand the technical side of this issue. Is anybody able to explain it?
 
dstruning said:
However, I still don't understand the technical side of this issue. Is anybody able to explain it?
Click to expand...

The F3 and many prior cameras use sgamut color science, this is Sony's old color science. Mainly it is harder to grade but not impossible. Your vimeo video is gone now so I didn't get to see it but I have shot some stuff on the F3 with slog profile forgetting to turn matrix off and yes it definitely gets some color skews to it. As Grug points out it's best to turn matrix off and you'll end up with a better start… even if its only in 8-bit 420 although generally that is a bit low for trying to record slog. 10-bit is far better if you can try to get a PIX240i or Blackmagicdesign shuttle v2 or something…

Here's more on the old and new Sony color science:

http://www.dvinfo.net/article/acquisition/sonyxdcam/sony_sgamut_vs_sgamut3.html
 
starcentral said:
... Your vimeo video is gone now so I didn't get to see it ...
Click to expand...
The video is still there...

starcentral said:
The F3 and many prior cameras use sgamut color science, this is Sony's old color science. Mainly it is harder to grade but not impossible. Your vimeo video is gone now so I didn't get to see it but I have shot some stuff on the F3 with slog profile forgetting to turn matrix off and yes it definitely gets some color skews to it. As Grug points out it's best to turn matrix off and you'll end up with a better start… even if its only in 8-bit 420 although generally that is a bit low for trying to record slog. 10-bit is far better if you can try to get a PIX240i or Blackmagicdesign shuttle v2 or something…

Here's more on the old and new Sony color science:

http://www.dvinfo.net/article/acquisition/sonyxdcam/sony_sgamut_vs_sgamut3.html
Click to expand...
Yes, there are color skews when you don't turn off matrix. And yes, it's much better to record in 10-bit... but what does the matrix exactly do? What is the background of that issue?
 
For several days I have been reading articles online around the old PMW F3 camera and S Log. I consider myself an intelligent human being and I think this is like trying to graduate as nuclear physicist in one year. I think all of the subjects surrounding color space, cameras and LUTs could easily fill an entire school program. I am surprise how much I am progressing....

I am shooting a feature with my F3 and the Odyssey 7Q. I shoot S Log Rec709 generally and CC in Avid MC. Not much in Resolve. I record 422 or 444 in an Odyssey 7Q recorder. Sometimes I shoot standard 444 gamma to the 7Q. Sometimes I "paint" a little with the PP when shooting with standard gamma. I almost never use the XDCAM footage although I think it looks great when is "cooked in the oven" and no much CC is needed.

Starcentral I am not only looking for best LUTs to bring the F3 "up to date" with the rest of the camera world, and this time I will learn to de-log with DaVinci but I am also interested in finding a way to use the internal XDCAM (I will sound a little the MacGyver show now) in the camera as a possible "offline" tool. Say instead of ProRes 4444 we shoot .DPX4444 (S Log or standard gamma), could we use the XDCAM as our off-line footage to later link to the 4444 footage in Resolve? I can "paint" the XDCAM with the internal LUTs in the F3 but they will be different to the LUT used in the 7Q recorder ....in any case I will have an easy to handle footage in a laptop and I could de-log when and after all footage (In final sequence of film) is linked to 4444 footage...? it may be not possible including using other LUTs like 3D LUTs in the F3 (I spoke to Sony and they say it is possible although not technically correct / risky) but I will never know if I don't ask. Thank you!

Sebastian
 
Hi Sebastian, did you read this thread? http://www.dvxuser.com/V6/showthread.php?323095-Sony-F3-Resurrection-The-New-Chapter It might help.

As for F3 with an internal "LUT" while putting Slog out to external recorder, I don't remember this in great detail anymore. I'm pretty sure with the F3 whatever you do in camera is also coming out the SDI ports. So even though the F3 supports 1D internal LUT capability (which will lack saturation control) I don't think you can load any 1D LUT without affecting the output SDI.. but again I don't really know. Maybe someone will chime in. The F3 definitely does not support 3D LUTs.

These resources might also help you:

http://blog.abelcine.com/2012/03/19/s-log-and-the-f3-–-part-4-in-camera-look-up-tables/

http://blog.abelcine.com/2012/06/13/sony-f3-signal-routing-101/
 
I am going to jump in here.
Don't use LUT's !
And this just doesn't apply to the F3.
They take you further away from your delicate source material.
Treat SLOG like RAW.
Equalize your Blacks and Whites, make a correction for skin/midtones, etc. and save it.
Use that for the rest of your scenes in the same circumstance.

Believe me, almost every LUT I have seen here either destroys/distorts your image or actually creates just as much work to do once it has been applied as if you didn't have one at all.
 
Slog can only easily converted with a lut - issued by the manufacturer - anything else is a crap shoot

sony never issued any luts for slog1 - so the f3 is a crap shoot full stop.

but catalyst browse has a lut for the f3 - you could try that
 
For LOG and sgamut colourspace I recommend using a LUT in the grading process to get into rec 709. I use the Impulz LUTs alot and find them great for matching cameras also. I can easily bring slog3 from the fs7 and slog1 from the f3 into close proximity with those.

also now with LUTcalc you can just transform the LC709A LUT to work for slog1 I guess. Have not tried yet but might in he future.
 
I'm pretty sure I read Slog didn't need a LUT to grade because it is pseudo Log and not too far from REC709 with a bit of Log at the top. I know the gamut is labelled as SGamut but how much of that gamut does the F3 fill up? Probably not much and therefore it's not a million miles away from REC709 either. The other benefit Slog had was this it was contrasty enough to not require VF LUTs so it looked OK while shooting.

I'm pretty sure this is the thinking behind all the pseudo Log formats like CLog etc that you can bend it into shape with curves. Note this thinking predates more rigorous LUT workflows we enjoy right now.
 
Nirv said:
I'm pretty sure I read Slog didn't need a LUT to grade because it is pseudo Log .
Click to expand...

F3 is impossible to grade (did you own one?) - nothing looks real ever - its more mystical than any other log - I think designed for 12bit F35 footy which can go anywhere unlike even 10bit F3 pro res.

Yes Stockstad has the scandi look down.. looking really fantastic.. but that is the only look and it doesn't work for 80% of projects - the point of log is to choose a look in post, not be nailed into scandi land.. however nice a place it is.

S
 
Last edited:
morgan_moore said:
F3 is impossible to grade (did you own one?) - nothing looks real ever - its more mystical than any other log - I think designed for 12bit F35 footy which can go anywhere unlike even 10bit F3 pro res.
Click to expand...

I don't doubt you but looking at the curves in LUTCalc there' naff all between SLog, CLog and BBC WHP etc so I wonder what the technical reason for SLog being a bit of an oddball?
 
morgan_moore said:
F3 is impossible to grade (did you own one?) - nothing looks real ever - its more mystical than any other log - I think designed for 12bit F35 footy which can go anywhere unlike even 10bit F3 pro res.

Yes Stockstad has the scandi look down.. looking really fantastic.. but that is the only look and it doesn't work for 80% of projects - the point of log is to choose a look in post, not be nailed into scandi land.. however nice a place it is.

S
Click to expand...

I would have no problems getting an saturated "GH4" image from the F3 in slog, just not sure why you would want to when you can have nicer, more subtle tonalities etc.

Three examples I shot all graded to taste with the same base LUT (Impulz Kodak Vis3 50D 5203). Actually all of them very quickly graded and pushed to different looks:


Commercial:

https://www.youtube.com/watch?v=mTyROaahqCU

http://topout.se/

Music video:

https://www.youtube.com/watch?v=2GOUeB3dpng


I would argue that the videos show that you can get more than this from slog: https://vimeo.com/31455659
 
Edvard - I love the look you get I feel it is highly stylised (in a good way) but not 'properly' saturated.. say a job in the mediteranian - red beachball, yellow bikini blue sky - the F3 does not deliver this easily.
 
Nirv said:
I don't doubt you but looking at the curves in LUTCalc there' naff all between SLog, CLog and BBC WHP etc so I wonder what the technical reason for SLog being a bit of an oddball?
Click to expand...

If you are looking at a bendy line 0-255 you are not seeing colour saturation - just adding a curve does not de-log an image.
 
morgan_moore said:
Slog can only easily converted with a lut - issued by the manufacturer - anything else is a crap shoot

sony never issued any luts for slog1 - so the f3 is a crap shoot full stop.
Click to expand...

I found an ancient Sony PDF a long time ago and it looked like Sony had contracted FilmLight to provide the LUTs. But for some reason that never happened.
I'm betting the slog LUTs included with he Baselight may be those.

but catalyst browse has a lut for the f3 - you could try that
Click to expand...

Need to give those a try...

I've been using the slog curves that come with the Odyssey to de-log the footage with good results..


But Sony clearly dropped the ball on this one.
 
You must log in or register to reply here.
Back
Top