Yesterday, I was working on my 4:2:2 vs. 4:2:0 video
that many of you have been requesting
using the Sony a7 III, when I noticed something
very peculiar with the way that camera records S-Log.
Let's get Undone.
[offbeat music]
♪ Gerald Undone ♪
♪ He's crazy ♪
What's happening, everybody? I'm Gerald Undone
and with great gear comes great responsibility.
Comes great responsibili-trili-truss.
So, as I was saying, I was working on my 4:2:2 video,
which of course requires you to record externally
because the Sony only does 4:2:0 internally
and this testing of course required
a lot of flipping back and forth between
the recording captured on the Atomos
and the one captured internally on the Sony.
Now, I'm going to share my findings with you
on that whole 4:2:2 vs. 4:2:0 thing in a different video,
but while I was flipping back and forth,
I noticed that the S-Log images looked quite a bit different
internally vs. externally. This didn't happen in HLG
or in any of the Cines, but in both S-Log2 and S-Log3,
the Atomos was fed a different signal
than what was captured on the Sony's SD card.
Let me show you what I mean. So, if we go to Premiere Pro,
we have multiple clips of this Rubik's Cube.
Now, this one is Cine2, recorded externally,
as the label says, and then recorded internally,
you can see it looks almost identical.
Might be a slight difference in saturation,
but it's pretty much the same.
And if we go to HLG, the same idea.
This is external HLG and internal HLG.
Again, pretty much identical.
Now, if we go over to S-Log2 here though,
this is external on S-Log2 and this is internal,
and you can see that the internal version looks
quite a bit flatter than the external version does.
And if we look at the scopes, you can see a little bit better
what's going on here. So, this is external.
Look where it reaches up to and where it comes down to
and then switch to internal and it's almost like
the whole thing is being clamped down
and this made me think of something
because it looks visually similar to what happens
when you switch from full to legal range.
Now, for a quick, little explanation on what that means
if you don't know, let's take a look here at an RGB scale.
So, let me switch the waveform over to RGB
and you can see that it goes from 0 to 255 when on 8-bit.
If you have 10-bit, those numbers are bigger, obviously.
But this is the full range of RGB
and whether you're looking at photo and video editors
or even the monitor that you have,
you usually have an option to switch between full
and on displays, it might be limited,
but the limited range is from 16 to 235
and basically, it kind of squishes it down
but you lose the ability to reproduce
the absolute blacks and whites of that image because
you have a more limited range. If you have all the way
from 0 to 255 available, then that's known as full
or full range or full RGB, but if you have 16 to 235,
that's known as the legal range or the limited range
or sometimes even the video range,
depending on the device or software used.
Anyway, if you ever switched back and forth
between the two, then you would've noticed
that it looks a lot like what's going on here
when we switch between the external recording
on the Atomos and the internal recording on the Sony
and its being clamped by about the same amount.
So, to test this theory, I whipped up
a quick 16 stop DR chart and recorded the samples again.
Now, if you look over here at scopes,
you can see it goes well above 255, but if we switch
to the internal, you can see that clamping happening
and it goes below 255. But Premiere Pro has presets
for full to legal range conversion and vice versa,
if you just go up here and type in "legal",
you can see they're broken down by the bit depth,
but we're going to use the 8-bit ones,
so if on the internal recordings, which I'm saying
is clamped to legal range instead of full,
we use the "Legal to Full Range, 8-bit"
and just drop it on the clip. Now, if we switch
back and forth, we can see that it looks almost identical
to the external recording and we can also do
the reverse of that. So, if I undo that but instead
put a "Full to Legal Range" on the Atomos recording,
bringing it down to the same level of clamping,
and now we switch back to the internal.
Again, they look identical.
However, this doesn't completely solve the problem
because the colours are also different between
the two recordings and changing the range
doesn't fix that. Let's jump back over here
to the S-Log recording
and we'll switch the waveform back to RGB
and if we take a look at where the reds and greens
and blue values are here and then switch to the internal one,
we can see that the colours are being sort of squished in a way
that makes them look different. And even if we look
at the image here itself, when we switch back and forth,
the greens and the reds have a different level to them.
If we put a quick grade on these two clips,
we can really see it happen. So, this is external.
Look at the reds and the greens,
and also just how much green, in this case, not much,
is in the yellow, and then when we switch to this one,
there's more green in the yellow and the vibrancy
of the green versus the red changes.
Let's switch back and forth a couple times for you to see.
So, this is a bit of a problem if you're striving
for colour accuracy and also if you're trying to match
footage recorded internally with that recorded externally.
Now, earlier I said this doesn't happen on the other gammas,
but there's a bit of a caveat to that.
If you start recording with the S-Log
and then switch profiles to one of the other gammas,
it too will also get clamped down.
I have some samples to show you what I mean,
but essentially, say that you started recording on Cine2
and you set up the shot, you like the exposure
and everything is good, then you're fine.
It's going to look the same internally and externally.
But if you started recording on S-Log
and switch to Cine2 with the exact same profile
and the exact same settings, the Cine2 will now
be clamped down and look different
than your previous recording
and the colours will be messed up.
Now, to preemptively answer some questions
that are likely going to be raised by that claim,
one, yes you can change your picture profiles
while recording, as long as you assign it to a button.
You can't enter the menu while recording,
but if you set your picture profiles to a custom button,
like I set it to the recycling bin, then I can press that
while I'm recording and change the picture profiles
while on the fly. And two, why would you do that anyway?
If it causes a problem, wouldn't it make more sense
to start recording in Cine and leave it in Cine?
Why would you want to change your profiles
while recording? And that's a good point
because the clamping seems to be determined
by the profile that you're in when you start recording,
so as long as you start recording in a non-S-Log gamma,
you'll be fine and that's the reason why I'm pointing
this out because it gives us a work around.
If we do the opposite and start recording
in one of the other gammas like Cine
and then switch to S-Log, that clamping doesn't happen
and the colours are correct. Now, this one's going to be
a little bit more difficult to show in Premiere,
but I'm going to do my best. So, this clip here
started in S-Log, then we transitioned into Cine
and we can see over here on the waveform
that the clamping is already happening
because the S-Log isn't able to reach above the 255
like it should be able to. And if we switch over to Cine
at the end of the clip, we can see that it's also
being clamped down to 235. This is Cine2,
so it's normally from 0 to 255, but it's being clamped down
to that 16 to 235 range, and if we switch back
and forth between it and the external recording,
like this, we can see the external recording goes back up
to 255 and it's got much richer blacks.
Now conversely, if we switch over to this clip,
which started in Cine and transitioned into S-Log,
if we turn the external recording on,
we can see that it doesn't actually change
between it and the internal.
I'm switching back and forth right now, and...
if we go to the end of the clip to where S-Log is,
we can now see that S-Log comes all the way up
to about 109 where it should be and if we switch over
to the external recording, we can see that both
are able to reach up to their full ranges
and they look pretty much the same.
And this is what helped me figured out
which recording was correct because up until this point,
all I knew was that they were different.
I didn't know if the internal or the external
was the correct one. But my current theory is that
if all the other gammas match internally and externally,
except for the S-Logs,
and you can make the S-Logs match
by starting with another gamma that does,
then it's probably the S-Logs that are wrong.
But, it doesn't really make sense to me
why the S-Logs are being clamped since Cine4,
which is also capable of exceeding the range
and going all the way up to 109%
looks exactly the same internally and externally
and isn't being clamped at all.
So, it's got to be either a bug with the S-Logs
or a design choice to limit the range of them
to help with the camera's smaller codec
and limited bit depth. But what's interesting
is that people are always complaining
about the difficulties in grading the S-Logs
on these 8-bit Sony cameras and I agree with them.
I don't really recommend using S-Log on these cameras,
but when you use the full range S-Log,
it's actually easier to grade and I can't help but think
that removing this clamping that happens
would make for a much nicer grading experience.
Let me show you something in Premiere
that demonstrates this using a really quick
and sleazy grade. So, here is the external clip
and here is the internal clip. Again, the internal clip
has those higher levels and it's more clamped down.
So, I have a grade that I'm going to apply to each of them
that I already whipped up and if we go back and forth now,
we can see that they look pretty similar.
But if we actually look at what had to be done,
now again, I just did this quickly using the sliders,
but look at what had to be done to the full range S-Log
and let's switch over to the clamped range.
See how far I had to bring the blacks down
in order to get a similar image here?
And this is going to have some unwanted effects.
So, if we look in close over here where the shadows
start roll off, and then we switch back and forth
between that and the external one,
we can see that the external one
has a lot less colour noise
and is a lot less kind of, like,
amplifying the garbage that you don't want,
where the limited range one
has got this, like, purple glow and the rings continue
on some of the other orbs here as well
as we move across. Look at the fringing,
and then switch over here and the fringing is controlled.
Now, this is obviously an extreme test,
but it carries over in other aspects
because you really just can't push everything unlimited
that you want and if you already have,
you know, a certain range and you want to push it farther,
that's going to make that 8-bit codec have a harder job
than if you'd already kind of started
with the slightly better range exposed correctly.
Now, I like I said, I don't know if this was by intention
or a bug, but for me, it's been easier to work
with the one coming out of the Atomos
than the one recorded internally.
And like I was saying,
I prefer the colours of the full range one.
I find them to be more pleasing, but also more accurate.
But at least in the meantime I've discovered a workaround
to help those that do want to record S-Log internally
and maybe have an easier grading experience
or just match it to external recordings better.
All you have to do is map your picture profile selector
to one of your custom buttons,
start recording in one of the other gammas like Cine,
then switch to S-Log in the middle of your recording,
then expose your shot and you're good to go.
Lastly, for the sake of being thorough,
here's some other things that I tried
when troubleshooting this that did not make a difference.
I tried recording without using the Atomos,
both with the HDMI still connected,
but the Atomos not recording
and with everything completely disconnected
and it still happens,
even when the Sony is just recording by itself
and in that vein, I also tried it with a different SD card.
I tested it in 1080p and in 4K
and with different frame rate and codec combinations,
and I also tried changing the HDMI output options
and none of these things made a difference.
I tried using the built-in gamma display assist
which basically lets you view the Logs
with a bit of a LUT applied and I tried literally
every combination of picture profiles
including using S-Log with the Cine color
and using the Cine gammas with the S-gamut colour,
as well as every relevant mode on the top dial
and several drastically different exposure settings
and white balances. I did this a lot.
If I were to show you my timeline,
each time you see a cut, that's a different test I did.
I must have recorded well over 100 different samples.
But that did allow me to expand my data
for my original purpose of this video,
which was evaluating the differences between
8-bit 4:2:0 and 8-bit 4:2:2, but that'll have to wait
until the next video. But that's gonna be it for me.
I hope you found this video helpful or at least entertaining
and if you did, make sure you leave it the old thumbs up
and consider subscribing if you haven't already,
but if you did not find this video helpful or entertaining,
feel free to hit the dislike button twice.
Alright... I'm done.