X-T3 F-Log vs. HLG comparison

[androidlad]

Went out and shot a quick comparison between X-T3 F-Log and HLG picture profiles.

Camera was set to:

Manual WB 5300K

H.265 LongGOP 400Mbps 3840x2160 25p

Sharpness -4, NR -4, Color -4 (adjustable for HLG only)

Exposure matched based on each profiles base ISO

 

F-log raw, base ISO 640, f/5.6, 1/1250s

 

F-Log with "F-log/F-Gamut to AlexaX2" LUT, generated with LUTCalc:

 

HLG raw, base ISO 1000, f/5.6, 1/2000s

 

HLG with "BT.2100 HLG to AlexaX2" LUT generated with LUTCalc:

 

Conclusion:

Fujifilm decided to "rate" HLG profile's base ISO at 1000, while the underlying analog gain is the same as F-log (if you compare F-log and HLG at base ISO without compensating for exposure, the highlight DR is exactly the same).

When you respect the base ISO and compensate for the exposure accordingly, HLG offers around 2/3 stop more DR in the highlights than F-log.

BT.2100 HLG maps 18% grey at 22% IRE, while F-Log maps at 46% IRE. The HLG image looks significantly "darker" than F-Log and requires an aggressive LUT curve to bring it back to BT.709.

Noise level in the shadow area is identical, despite the aggressive push in HLG's LUTed image.

Although both F-Log and HLG were normalised to the same target colour space AlexaX2, there's a visible difference in the tonal range (they were shot less than 5 seconds apart so it has nothing to do with ambient light level.)

Personally, for high contrast scenes I'd definitely use HLG over F-Log. Note that it's vital to get the exposure spot on with HLG in order to take full advantage of the expanded DR.

 

[thebrothersthre3]

Pretty cool! Thanks for the test. 

[DanielVranic]

Tbh I think i still like the Flog tbh, but that HLG does look great.

What is the exposure requirements for it? I have never shot HLG in my life...

[mercer]

Yeah I prefer the F Log as well. It’s way more dramatic looking. While the HLG looks like it could have been shot on a phone or a camcorder. Even the color tonality looks better with the F Log... in my opinion. 

Are there any HLG to F Log to Alexa LUTS floating around? If so, maybe that would have a better effect. 

[androidlad]

51 minutes ago, mercer said:

Yeah I prefer the F Log as well. It’s way more dramatic looking. While the HLG looks like it could have been shot on a phone or a camcorder. Even the color tonality looks better with the F Log... in my opinion. 

Are there any HLG to F Log to Alexa LUTS floating around? If so, maybe that would have a better effect. 

I like HLG colour.

Yes HLG is less contrasty, but it can be easily added with some simple grading. I find that HLG completely removes the magenta bias that plagues F-log since it was introduced in X-T2. Also the roll off is even smoother. It's very Alexa like.

[DanielVranic]

1 hour ago, androidlad said:

I like HLG colour.

Yes HLG is less contrasty, but it can be easily added with some simple grading. I find that HLG completely removes the magenta bias that plagues F-log since it was introduced in X-T2. Also the roll off is even smoother. It's very Alexa like.

Xt3 doesn't have the magenta FLog thing

 

[androidlad]

Just now, DanielVranic said:

Xt3 doesn't have the magenta FLog thing

 

It does.

[deezid]

 

2 hours ago, mercer said:

Yeah I prefer the F Log as well. It’s way more dramatic looking. While the HLG looks like it could have been shot on a phone or a camcorder. Even the color tonality looks better with the F Log... in my opinion. 

Are there any HLG to F Log to Alexa LUTS floating around? If so, maybe that would have a better effect. 

Just make it more dramatic then?

@androidlad care to upload some uncompressed footage?
Wondering about skin above ISO1600 (lost lots of texture doing my first tests)
 

[DanielVranic]

2 hours ago, androidlad said:

It does.

I have never experienced it. I have also not used any LUT's to grade my XT3 stuff, just Resolve curves and 2020-709 color space.

With LUTCalc, what are you using? I tried to make the AlexaX2 from FLog one, and the highlights got NASTY!

[androidlad]

1 minute ago, DanielVranic said:

I have never experienced it. I have also not used any LUT's to grade my XT3 stuff, just Resolve curves and 2020-709 color space.

With LUTCalc, what are you using? I tried to make the AlexaX2 from FLog one, and the highlights got NASTY!

The magenta bias shows up in large gradients like sky, even in 10bit 400Mbps. It's completely absent in HLG and the codec/bitrate are exactly the same

FLog_FLogGamut-AlexaX2_AlexaX2.cube

[DanielVranic]

Not the biggest fan of what that LUT does to the highlights, I messed around a little bit with mine.

 

Arri3.cube

[BrunoCH]

3 hours ago, androidlad said:

It does.

What is your NLE? I saw something like this ugly thing on the FCPX viewer, but the export fixes that. And this magenta Flog thing isn't on the export.

[androidlad]

9 minutes ago, DanielVranic said:

Not the biggest fan of what that LUT does to the highlights, I messed around a little bit with mine.

 

Arri3.cube

Yours compresses highlight to almost where skintone should be.

On properly exposed F-Log materials, the default F-log to Alexa LUT work really well, you can choose Amira option for a tad more contrast. If you think it does bad things to your highlights you might be overexposed, in that case you can generate LUT sets that compensate for over/underexposure.

[Attila Bakos]

18 hours ago, androidlad said:

BT.2100 HLG maps 18% grey at 22% IRE

Where do you get the 22% from? I couldn't find it in the specs.

I also did my tests with the X-T3 when the update arrived. I used ETTR and placed highlights at the exact same level near clipping, then pushed shadows to the same level in post. Overall noise level was identical, and to my surprise I could get a little more detail out from the shadows of HLG even though they appeared more crushed. The difference is very little though, I wouldn't base my choice on it. I've chosen to stay with F-Log, because I learned to work with it in the past and I find it easier now.

[androidlad]

3 minutes ago, Attila Bakos said:

Where do you get the 22% from? I couldn't find it in the specs.

I also did my tests with the X-T3 when the update arrived. I used ETTR and placed highlights at the exact same level near clipping, then pushed shadows to the same level in post. Overall noise level was identical, and to my surprise I could get a little more detail out from the shadows of HLG even though they appeared more crushed. The difference is very little though, I wouldn't base my choice on it. I've chosen to stay with F-Log, because I learned to work with it in the past and I find it easier now.

From LUTCalc data.

HLG was not designed to be an acquisition format, the curve is extremely non-linear and hard to grade manually.

I think HLG does offer a bit more shadow detail due to its efficient use of all available bits, compared to F-Log's more compressed tonal range (elevated black level). 

I'm really starting to like HLG more, mostly because the new colorimetry, it's more clean and neutral.

[Attila Bakos]

16 minutes ago, androidlad said:

From LUTCalc data.

HLG was not designed to be an acquisition format, the curve is extremely non-linear and hard to grade manually.

I think HLG does offer a bit more shadow detail due to its efficient use of all available bits, compared to F-Log's more compressed tonal range (elevated black level). 

I'm really starting to like HLG more, mostly because the new colorimetry, it's more clean and neutral.

But in LUTCalc you can choose between NHK / BBC reference white scaling, and the BBC one gives you 38% IRE for 18% grey, which I believe is closer to what's happening in the X-T3 when you let the camera figure out middle grey. I filmed a lastolite middle grey background filling the entire frame and I could only see about 10% IRE difference between F-Log and HLG.

[DanielVranic]

Ok so I attached the wrong LUT, my bad.

Did a whole bunch of testing and I am still on the fence about HLG on this camera? I never really used LUT's to grade my FLog, and I feel that is why that magenta is occurring...

I always make 3 nodes,

1. monochrome/WB fix,

2. Curves with splines to get the S-Curve

3. Color Space Transform 2020-709

And typically after that, I will do another color space transform to get the Alexa Gamma, and then back to 709 and do some LGG to get my shadows and stuff right. 

^^^i do this only for a "look",  the first 3 steps are really the meat. and potatoes 

 

[thephoenix]

hlg comes with the latest update ?

 

[thebrothersthre3]

10 minutes ago, thephoenix said:

hlg comes with the latest update ?

 

yes sir

[thephoenix]

thanks. will wait for the bug fix before updating and testing