F55: S-Log2 Thoughts after testing a little

Nate Weaver

Nate Weaver

Veteran
S-Log 2 seems to the opposite of what I thought it would be.

Instead of being more extreme, it's actually less so and maybe more in line with what Canon does with their Log.

What I can't figure out though is just how much of the sensor's range is being mapped into S-Log2. By eye, it looks like there is no more latitude than F3 S-Log, but I know my eyes can deceive, so I'm not judging quite yet. I have not had the camera out in a daylight exterior situation which would make it easier to get an idea..

Another comparison might be Alexa's Rec 709 mode.

So far though, in conjunction with the S-Log 2 LUT I received a couple weeks ago from Joel Ordesky of the F65 team, I have very nice images with nice highlight rolloff.

One other note...I noticed when used with this new S-Log 2 LUT from Joel, the difference in exposure from camera to screen is much less, so if you expose by eye without a LUT in camera, after applying the LUT your exposure is more or less the same. What this means for the guideline of exposing 18% gray so it hits 30IRE, I do not know.

[edit: I've made a test video of one clip back to back with itself, one LUT'd and one no-LUT. Rethinking my thoughts above, now S-Log2 seems flatter to me. Will post vid in this thread shortly]
 
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Thanks for the insight Nate. Would it be possible to share Sony's new LUT? If it can be attached in a email, could I get a copy from you? bill at billthomasphoto dot com

Picking up my camera on Monday and would love to test it out.

Thanks in advance
 
I just sent you an email.

Here's one thing about that LUT though...it expects S-Gamut color scaling along with S-Log 2 gamma. My 55 can record S-Gamut to XAVC...but you F5 cannot

I suspect colors might be a little oversaturated...with some particular colors maybe going off the map, so to speak. Greens and reds would be my guess. I tried the same LUT on F3 material maybe two weeks ago and I remember red taillights, something weird happened with them.
 
Nate Weaver said:
I just sent you an email.

Here's one thing about that LUT though...it expects S-Gamut color scaling along with S-Log 2 gamma. My 55 can record S-Gamut to XAVC...but you F5 cannot

I suspect colors might be a little oversaturated...with some particular colors maybe going off the map, so to speak. Greens and reds would be my guess. I tried the same LUT on F3 material maybe two weeks ago and I remember red taillights, something weird happened with them.
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Good to know, thanks. Just emailed you back.
 
Its interesting Nate, some of the frame grabs I've seen, and even footage shot in "slog2" looks nothing like what I know F3 slog to look like. slog2 appear less milky and more saturated. Defniltey not as flat a F3 slog... would you agree?
 
PaulReam said:
You can choose between Normal or S-Gamut color space on the F5 menu?
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No. S-Gamut is F55 only. S-Gamut is the recording colorspace enabled by the output of the F55/F65 new color filter array on the sensor. Or put another way, if you have that color filter array, to record it properly to a YUV recording format you need S-Gamut.

And to do it "right", you need a LUT in post that knows what to do with that color mapping. I mean, just like S-Log, you can do it without, but you may see some color stuff happening that you may not expect.

In general, to the eye, S-Gamut looks less saturated, because it saves the extremes of the recorded data for really extremely saturated color that other cameras clip or mis-map. A colorist on Twitter, Juan Salvo, posted a still from a 55 clip of a neon sign in NYC. The 55 handled the high level of saturated color perfectly in the still.

PaulReam said:
In fact, switching to S-Gamut forces the gamma into S-Log2?
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That part is right. It also disables any color matrix adjustments in the Paint menu. But only on the 55.

starcentral said:
Its interesting Nate, some of the frame grabs I've seen, and even footage shot in "slog2" looks nothing like what I know F3 slog to look like. slog2 appear less milky and more saturated. Defniltey not as flat a F3 slog... would you agree?
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S-Log 2 on the F5 is just like S-log on the F3 with Picture Profiles. You can enable any color settings you want. Not like the F3 with the S-Log upgrade where when you turned on S-Log it locked you out of color matrix/saturation changes.

So if somebody shoots S-Log 2 on the F5, color rendition is totally up in the air, because they can go in and enable any matrix setting Not to mention, just how did they de-log it? There's too many way s it can be screwed up. That's why I'm not flipping out when I see weird highlights on F5 footage, there's too many ways to goof it up, both in camera and post. Typical Sony, they give you 20 ways to screw up your image and only one way to make it look awesome.
 
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Nate Weaver said:
No. S-Gamut is F55 only. ...In general, to the eye, S-Gamut looks less saturated,
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Maybe they've given me a F55 by accident then, because that's exactly what I see when I choose 'S-Gamut' from the color space menu on my F5 !!!

The S-Log2 image appears less saturated and slightly more milky when recorded XAVC 10-bit. If you choose S-Gamut the gamma goes into S-Log2 by default.

Are you saying the F5's are not supposed to do this? If so we've discovered another firmware bug!

F5-1.jpg
 
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Nate I couldn't agree more - there will definitely be many combinations of results that are up in the air if slog2 is simply PP with access to all other menu options. Even when I shot slog on F3 using PP I still left everything else set to default values so that in post I could preserve my "sanity".

Anyway I get my new F soon enough then most definitely I will spend more time analyzing and testing settings, footage and LUTs far more than actually using the camera to shoot with. :huh:
 
PaulReam said:
Maybe they've given me a F55 by accident then, because that's exactly what I see when I choose 'S-Gamut' from the color space menu on my F5 !!!

The S-Log2 image appears less saturated and slightly more milky when recorded XAVC 10-bit. If you choose S-Gamut the gamma goes into S-Log2 by default.

Are you saying the F5's are not supposed to do this? If so we've discovered another firmware bug!
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Ay. I was making an assumption based on some other F5/55 menu differences, and the nature of the 55 CFA vs what came before it. Apparently a bad assumption. Thanks for not hanging my out to dry :-)

The 55 records color info differently than the 5, based on the sensor CFA, so I assumed they enabled S-Gamut on the 55 because of that. I know the matrix settings between the two are different.

It doesn't change the fact though that the 55 can put more useful info into that S-Gamut output than the 5 though. I bet they enabled it because if they did it right, it will make the two cameras match when you have the two together.


Osslund said:
So there's no "pure" s-log like on the F3 with RGB key installed?
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There kinda is. If you enable S-Gamut it locks a lot of options out like the F3 used to. I like it that way.
 
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I think I might have been too hasty in my judgement of S-Log 2.


I know it does indeed though go down to 0 on the blacks, which Log-C does not.

Here's a screencap of some Alexa Log-C vs S-Log2 pointed straight at the sun. Both unmodified, straight from camera. Similar stops, but not identical of course.


Screen Shot 2013-03-02 at 3.12.20 PM.jpg
 
First thing I noticed about that short video (aside from it looking good) is his exposure seems spot on for the scene while retaining detail in the sky and a lot of the sun when he tilts up. With that, when he shows the ungraded version it doesnt have that 1-2 stop underexposure look that S-Log usually has when exposed "properly". I guess my assumption or question is, does S-Log2 look less underexposed when set at 33% on a 18 grey? ..or maybe he exposed it a 50%(overexposed) but S-Log2 has so much range the sky didnt clip. That would be nice..

**Ha!, just realized Nate shot it. So replace "he" with "Nate" and with that, Nate how did you expose for the scene?
 
Fotojorno said:
First thing I noticed about that short video (aside from it looking good) is his exposure seems spot on for the scene while retaining detail in the sky and a lot of the sun when he tilts up. With that, when he shows the ungraded version it doesnt have that 1-2 stop underexposure look that S-Log usually has when exposed "properly". I guess my assumption or question is, does S-Log2 look less underexposed when set at 33% on a 18 grey? ..or maybe he exposed it a 50%(overexposed) but S-Log2 has so much range the sky didnt clip. That would be nice..

**Ha!, just realized Nate shot it. So replace "he" with "Nate" and with that, Nate how did you expose for the scene?
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By eye, since I don't have any proper tools in camera to figure it out.

BTW, that S-Log2 LUT that came from Sony, it is not pulling a 30IRE 18% gray up to 50IRE. I just did some sleuthing in Resolve and figured that out. That particular LUT takes 30IRE and raises it to only 38IRE. Maybe that's the way they want it.

So, using that LUT in post, you can expose by eye and get nice looking pictures. What that means for rated ISO while shooting though, I do not know.
 
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Nate Weaver said:
By eye, since I don't have any proper tools in camera to figure it out.

BTW, that S-Log2 LUT that came from Sony, it is not pulling a 30IRE 18% gray up to 50IRE. I just did some sleuthing in Resolve and figured that out. That particular LUT takes 30IRE and raises it to only 38IRE. Maybe that's the way they want it.

So, using that LUT in post, you can expose by eye and get nice looking pictures, but it's no longer a 1250ISO camera doing it that way. It's probably half that.
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I completely follow what your saying. Well if the mids are only LUTT'ed up to 38%, thats surprising as they definitely dont look underexposed. Weird ..and good I guess. Looking at your pre-LUTT'ed S-Log footage in Resolve, do you feel the rough mid-grays(asphalt, sidewalk) came in around 30-33%?
 
atarijedi said:
It is weird to see some of those quick camera movements without any sort of jello effect.
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Was just going to type same thing and then saw you beat me to it. The lines of the building walls staying so straight actually seemed a little odd by being so normal.

Thanks for sharing all the info Nate. Very nice for everyone else when someone is prepared to put themselves out there as the Guinea Pig and work all these things out.
 
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