F3: S-Log oversaturates green channel

Nirv said:
The music video is superb.

There's been a bizarre product life cycle with the F3, I thought it was an over priced FS100 when introduced and now looks like one of the bargains of the decade as it reaches EOL (as far as Sony is concerned not the users).
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I don't think I would lump it in with the FS100. Supposedly the F3 and F5 sensor share a good amount of DNA and officialy Sony considers it part of the Cinealta lineup (even if they treat it like the red headed stepchild of the family).

To my eye the F3 image does not look like the prosumer FS series.

But regardless at current used prices it's an absolute steal. All you need is LUTs
 
I've developed a solid starting point for grading looks with the F3. I created a custom Slog picture profile using the alchemy of the color matrix. Green color cast gone. I then move to post -- using a combination of an ACES 0.0.1 LUT (input node) and a custom LUT created from LUTCALC (output node) in Davinci Resolve. The LUTCALC LUT utilizes the output gamma Panasonic Varicam V709 while output gamut moves to Sony S-Gamut3.cine. LUTCALC is highly recommended and thank you Ben Turley for creating this versatile tool. There are many things that go into your 'look' - starting with lens choice, color temp choice, exposure, filters, and on an on....be sure to do your own testing if you delve into the F3's color matrix --- and remember to color balance your lenses using LUTCALC (if you're using photo lenses like I am) so you can easily drop in a custom LUT to any lens that might have a warm/cool shift.

These quick grabs use the Luts mentioned above. No color grading has been done in post.

cheers, Paul

F3 - Thnksgiving 5.jpgF3 - Thnksgiving 4.jpgF3 - Thnksgiving 3.jpgF3 - Thnksgiving 2.jpgF3 - Thnksgiving 1.jpg
 
The roll of Slog1 compresses the 'highlights' from about 50 (out of 100) leading to lack of tonality.. pulling back proper contrast is either really hard.. or maybe impossible unless one records 12bit

Nirv - did you see the PM

S
 
morgan_moore said:
The roll of Slog1 compresses the 'highlights' from about 50 (out of 100) leading to lack of tonality.. pulling back proper contrast is either really hard.. or maybe impossible unless one records 12bit

Nirv - did you see the PM

S
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Don't agree. That lack of tonality is from the grade, not the info. I get a lot more nuance with plain old SLOG than that. In fact I have seen more aberrations in SLOG2 and SLOG3 than in the original.
 
morgan_moore said:
The roll of Slog1 compresses the 'highlights' from about 50 (out of 100) leading to lack of tonality.. pulling back proper contrast is either really hard.. or maybe impossible unless one records 12bit

Nirv - did you see the PM

S
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Not had time yet, sorry.

What were you shooting with your F3? 8 bit Slog or to a 10 bit recorder?
 
Nirv said:
Not had time yet, sorry.

What were you shooting with your F3? 8 bit Slog or to a 10 bit recorder?
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It was my main camera for six months - but many jobs needed 60p so the FS100 got a lot of play.

I shot internal 'BBC' settings for light 'work', I shot 2 drama shorts with Slog 10bit.

I shot a couple of corporates Slog10bit. The mass of the camera+shuttle+monitor+vlock was a nightmare for solo shooting.

I tinkered no end in the studio trying to get a look. And also tested against the BMC4k for 'nelson nutmeg' - the BMC4k ripped it apart for colour resolution mass and simplicity.

Id had the camera for six months and the FS7 was released.

I sold the F3 never having got a proper image from it, I was getting nice stuff from the FS7 after one morning.

The F3 is scrap IMO. Only useful for the 'Stockstad' look.. which is indeed pretty!

Can one do 12bit with the Ody? That might be interesting. Id sold it before the Ody was affordable.. the other recorders were the SR or Codex which are antique lumps and impractical and unafordable.

S
 
morgan_moore said:
It was my main camera for six months - but many jobs needed 60p so the FS100 got a lot of play.

I shot internal 'BBC' settings for light 'work', I shot 2 drama shorts with Slog 10bit.

I shot a couple of corporates Slog10bit. The mass of the camera+shuttle+monitor+vlock was a nightmare for solo shooting.

I tinkered no end in the studio trying to get a look. And also tested against the BMC4k for 'nelson nutmeg' - the BMC4k ripped it apart for colour resolution mass and simplicity.

Id had the camera for six months and the FS7 was released.

I sold the F3 never having got a proper image from it, I was getting nice stuff from the FS7 after one morning.

The F3 is scrap IMO. Only useful for the 'Stockstad' look.. which is indeed pretty!

Can one do 12bit with the Ody? That might be interesting. Id sold it before the Ody was affordable.. the other recorders were the SR or Codex which are antique lumps and impractical and unafordable.

S
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I guess worrying about the F3 is a bit moot now that the FS7 is here and producing such amazing images with zero effort. The FS100 and ND faders almost put me off cameras for life as Sony did everything to compromise that camera with the choice of gamma curves so they weren't quite right in most situations and combined with the variable WB device aka the ND fader it was an offing nightmare. Fortunately Sony seems to have woken up and delivered the FS7.

There's no doubt that the F3 can produce some lovely images as Stockstad so very capably demonstrates. Owning a 4K camera and producing sharp HD I'm surprised how little I give a **** for resolution and prefer the softer image that the F3 process.
 
Just skipped through this.

We are all aware that there is a big difference between an Slog gamma curve and the SGamut colour space?

The problem with all these LUTs is that they try to do lots of things at once, and that's not ideal. They get a bad rep because of that. The impulse LUTS are creative looks that concatenate many transforms into one.

I don't have an F3, and have no vested interest so not sure if anyone even cares, but...

- A 1D LUT can transform the tone curve of Slog2 to a different curve, be that linear (for something like resolve) or Rec709 for display. The LUT calc is showing these tone curves. Many log curves are very similar. There are a couple of nice looking 709 tone curves, personally i like the 709A curve for display. But only for display, i don't want to work in that curve.

- A matrix operation can losslessly transform from one colorspace to another. If you view an SGamut image on your sRGB display it will look wrong, the colours will be off. If you transform that SGamut to 709 or sRGB then the colours *should* look correct. If they don't look correct then there's something up with the recording. This green issue could just be not transforming the colorspace. LUTCalc uses this matrix calculations internally to do that. This transform is a 3x3 matrix calculation, based on the primaries of the various spaces. It's not voodoo.

- SGamut is made more difficult because Sony have baked white balancing information into their LUTs, this complicates things in ways i'm not sure about because no system i've seen makes allowances for that. Nuke et al just have a set of primaries for SGamut

Now a look LUT from impulse is a way of baking a series of those steps into one and it's not reversible. All of the above steps can be reversed but a 3D LUT may not be. Two source colours that are different can end up the same colour via a look LUT. So it's a one way journey and something that ideally should be at the end of the chain but then you can't grade under it.

So an ideal workflow, depending on your application, would be

Linearise your tone curve
Convert any colorspaces
Grade like crazy
Perhaps, maybe, add a simple look LUT at the end (maybe a film print emulation)

Done!

There's just too much misunderstanding with LUTs these days

cheers
Paul
 
Just made a basic rundown on the visual steps Im going for when quickly grading the F3. Tried to choose a frame that had high contrast and some skin, red and green in it. This was just a quick job:

http://edvardstokstad.se/quick-step-by-step-grading/


Edit:

I just tried a LUTcalc made version of LC709A made for Slog and Sgamut. Seems to work like it should, definitively getting those pink/purpleish reds. Will try next to a FS7 soon to see if they match.
 
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Thanks Paul!

Thats a good explanation. Although I would argue that that with the Impulz LUTs you can just choose one that fits you look and then do adjustments before or after the LUT depending on your needs. I would like to have LUTs for neutral transforms before grading also, but in my experience the more LUTs you use, the more strain you put on the footage also and you will have noise creep in there. For the F3 in ProRes HQ I think that 2-way LUT (for example into cineon and back) is pushing what the file can handle.
 
stokstad said:
Just made a basic rundown on the visual steps Im going for when quickly grading the F3. Tried to choose a frame that had high contrast and some skin, red and green in it. This was just a quick job:

http://edvardstokstad.se/quick-step-by-step-grading/


Edit:

I just tried a LUTcalc made version of LC709A made for Slog and Sgamut. Seems to work like it should, definitively getting those pink/purpleish reds. Will try next to a FS7 soon to see if they match.
Click to expand...

I generally work with an RGB Parade, but your waveforms are showing cyan blacks. First thing I would do is equal out the bottom end. I also feel you have got some orang-ish skin going on there. So I see a cross between cyan and red's. This is typical of most LUT's that are not balanced out properly. I would focus in on the skin tone of one the people (the lady's legs in the background) and see how closely it falls to the skin tone diagonal in your vector scope between yellow and red (there should be an option for it somewhere). Could be some adjustment is needed there. If you can hold the skin back in a secondary, but let the rest remain saturated you will have a nice little shot...anyhow that's what I would do.
 
stokstad said:
Just made a basic rundown on the visual steps Im going for when quickly grading the F3. Tried to choose a frame that had high contrast and some skin, red and green in it. This was just a quick job:

http://edvardstokstad.se/quick-step-by-step-grading/


Edit:

I just tried a LUTcalc made version of LC709A made for Slog and Sgamut. Seems to work like it should, definitively getting those pink/purpleish reds. Will try next to a FS7 soon to see if they match.
Click to expand...

I've just got deep sun tan off the woman's nuclear trousers.
 
Just making a guess. New to camera science, in my first year of Uni.

Would it have something to do with the low pass filter not doing it's job properly. Typically a low pass filter is implemented to help correct colour sampling errors found when using a Bayer pattern colour filter. I've been seeing the same problem with my camera. Not sure if this is right and it certainly does not help solve the problem. Just find it interesting as to why this problem occurs. Looking forward to when we start seeing more Foveon type colour filter cameras.
 
stokstad said:
Just made a basic rundown on the visual steps Im going for when quickly grading the F3. Tried to choose a frame that had high contrast and some skin, red and green in it. This was just a quick job:

http://edvardstokstad.se/quick-step-by-step-grading/


Edit:

I just tried a LUTcalc made version of LC709A made for Slog and Sgamut. Seems to work like it should, definitively getting those pink/purpleish reds. Will try next to a FS7 soon to see if they match.
Click to expand...

At the end of the day it's a personal decision how you want to go about grading. My pipeline tends to be more vfx based therefore i like to have photometrically accurate images - meaning that i like to convert logs into scene linear. Then any operations, like motion blur, are done accurately because the light levels are the same as the real world.

Manually bending the log into a tone curve is fine, but each log curve tends to mess with the shadows slightly differently and to me it's a bit like using a hammer - not very precise. I'm not a fan of using gamma etc for exposure changes, i find gains in linear space quicker and easier, especially when combining overlapping exposure adjustments.

It's very easy to go crazy on the Reds in sRGB colorspaces.

Totally IMHO though.


stokstad said:
Thanks Paul!

Thats a good explanation. Although I would argue that that with the Impulz LUTs you can just choose one that fits you look and then do adjustments before or after the LUT depending on your needs. I would like to have LUTs for neutral transforms before grading also, but in my experience the more LUTs you use, the more strain you put on the footage also and you will have noise creep in there. For the F3 in ProRes HQ I think that 2-way LUT (for example into cineon and back) is pushing what the file can handle.
Click to expand...

Of course, it depends what you're going for. I've noticed some issues with banding in some look LUTS though, be aware of that.

Also the app you use to apply the LUTs can make a difference because a LUT is a set of 3D transforms but it is finite. So it's up to the app to interpolate the values between the steps and there are various approaches to that. It's interesting to take a look LUT and view footage with the interpolations set different, from none to various bicubic variants.

cheers
Paul
 
stokstad said:
Just made a basic rundown on the visual steps Im going for when quickly grading the F3. Tried to choose a frame that had high contrast and some skin, red and green in it. This was just a quick job:

http://edvardstokstad.se/quick-step-by-step-grading/


Edit:

I just tried a LUTcalc made version of LC709A made for Slog and Sgamut. Seems to work like it should, definitively getting those pink/purpleish reds. Will try next to a FS7 soon to see if they match.
Click to expand...

The web page the link goes to is gone now, may you please restore it? :) As a fellow F3 shooter I'm quite curious to read it :)
 
"Typically a low pass filter is implemented to help correct colour sampling errors found when using a Bayer pattern colour filter."

I thought it was there to stop fixed pattern moire artifacts.. ? or it that the same thing..?
Thanks
 
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