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Author Topic: ETTR, Zebras, zone system etc...in video  (Read 3679 times)

fredjeang2

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ETTR, Zebras, zone system etc...in video
« on: January 28, 2016, 10:16:12 pm »

Hi,
In this topic I'd like if we could share our experiences regarding exposure techniques in video.

I'd start with a few thoughts and questions.

So far I've been using more extensively the zebras (setted at 95%) in the holy mantra spirit of ETTR. I must admit that it worked quite well in most cases and it is a fast way, but on the other hand I noticed that I'm loosing more and more the sense of "thinking the exposure" relying on those electronic helps. (in fact I use zebras + histogram in capture as electronic helps).

As I said, it Works, in the sense that it is averagely "right", reliable...BUT...I can not get to the point where I got something more than correct. In other words, it lacks personality. It is "flat" if I might say. Predictible.
We know that good DPs are the one who precisely break the rules, the average, the norms. That's why they are good. But, where to break?

The prob I see is that highlights aren't recoverable if blowned but shadows are recoverable at the cost of artifacts.

After Reading a thread in the Red forum (and even the Alexa crews) in wich many DP demystified the ETTR mantra in motion capture but were more (without naming it directly) into a sort of zone system idea. (bloody hell, I studdied the zone system in my youth when I was in fine arts and never used it later-on...is it still valid today?)

What do you think? talking motion of course.

PS: it is particularly interesting to have imputs on this topic in Lu-La IMO because as there are mostly photographers doing motion and not the other way, we could get interesting imputs to compare what they would do in motion they would not in stills and vice-versa.
« Last Edit: January 28, 2016, 10:24:51 pm by fredjeang2 »
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Christopher Sanderson

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Re: ETTR, Zebras, zone system etc...in video
« Reply #1 on: January 29, 2016, 11:18:22 am »

Zebras: Useful as part of judging accurate exposure. When shooting Rec709,  I set Zebra 1 to 70% for properly exposed skin tones and (if available) Zebra 2 to 105% to show areas of irrecoverable over-exposure. Generally I use a light-handed Cine gamma

That being said I still prefer my eye and a EVF with which I am familiar. I do not use 'false colour' as that tends to be too much information to process on the fly ))

ETTR is really only useful for RAW video (which I do not and do not anticipate using near-term due to workflow) AND for S-Log where it is critical to not under-expose the shadows and introduce unnecessary noise.
« Last Edit: January 29, 2016, 02:17:17 pm by Chris Sanderson »
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fredjeang2

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Re: ETTR, Zebras, zone system etc...in video
« Reply #2 on: January 29, 2016, 01:58:46 pm »

Thanks Chris.

I abandoned also Raw workflow and no plan either
To use it again in a near future unless I'd go Red. I absolutly
Hate Arriraw workflow and semi-hate cinema DNG.
Prores HQ and even 422 in 90% of the cases are more than
Enough for my needs, they deliver great stability.

But yes I do shoot log and agree with you on ETTR
In log config cause shadow recovery is not very nice
(not to say ugly) If we screw it.

But I'm still missing a point: I was watching Goldfinger and
Even Dr No. We know wich film has been used. They have less
Stop DR than we have now in digital and no clipping nor
Lacking details in shadows. How did those dudes acheive
That? The thing is that if you grab a Goldfinger scanned image,
And you push it to limits in post, (in your favorite grading software), it stands better than most of our
Digital files. Something knew those guys that seems to
Have been lost in our digital age. I'd like to know what it is.

Ps: I did this testing some months ago on a scanned image
Of the scene where Bond is been presented the Aston Martin,
So it is an interior low light scene and I was shocked to
Discover how far you could push this image in post...

Is a good old lightmeter completly obsolete today?
« Last Edit: January 29, 2016, 06:15:29 pm by fredjeang2 »
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Christopher Sanderson

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Re: ETTR, Zebras, zone system etc...in video
« Reply #3 on: January 29, 2016, 02:15:03 pm »

...They have less
Stop DR than we have now in digital and no clipping nor
Lacking details in shadows. How did those dudes acheive
That?....

I wonder if it is not BECAUSE they lit everything to an 8 - 9 stop range that you can now push those eight stops all over the place within today's 12 - 14 stops?

We could learn something there!

fredjeang2

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Re: ETTR, Zebras, zone system etc...in video
« Reply #4 on: January 29, 2016, 02:18:56 pm »

I wonder if it is not BECAUSE they lit everything to an 8 - 9 stop range that you can now push those eight stops all over the place within today's 12 - 14 stops?

We could learn something there!

Very interesting point Chris! Brilliant. That can make sense.
Indeed.
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fredjeang2

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Re: ETTR, Zebras, zone system etc...in video
« Reply #5 on: January 29, 2016, 02:22:05 pm »

But...how can we light-expose on purpose within a limiting
Range of DR? Zebras at 85% ?

My idea would be lite for the shadows instead of the midtones
And limiting the max highlights with a zebra setting.
But I'm not sure, just the idea that comes in mind.
« Last Edit: January 29, 2016, 02:31:00 pm by fredjeang2 »
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fredjeang2

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Re: ETTR, Zebras, zone system etc...in video
« Reply #6 on: January 29, 2016, 02:41:06 pm »

I've just runned a quick test in my flat with a beauty box. Yes, it seems that
Your idea goes in the right direction.

Got zebras at 80 and as it is controled light I can lite the shadows
Instead to avoid having to recover. So my DR is limited on purpose
And then in post it gives much more stops of room.

That is only possible in controled light, but Goldfinger was
All in controled light. That works!!

Chris, you're a genius. That was really helpfull.
So it is a complete change of mentality: lite the shadows
Over other considerations and limit your max highlight.
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Christopher Sanderson

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Re: ETTR, Zebras, zone system etc...in video
« Reply #7 on: January 29, 2016, 02:53:08 pm »

Yes, if you have the 'luxury' of controlled light and work with an incident meter for gamma and spotmeter for blacks & highlights - then you can place the scene within your 'good' DR.

If however you have little or no control over the light, then fall back on S Log for post control or—as I do—use a light cine gamma and accept that you will have some irrecoverable blacks and highlight burnout...

Morgan_Moore

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Re: ETTR, Zebras, zone system etc...in video
« Reply #8 on: January 30, 2016, 01:36:52 pm »

Fred - I think it depends on your camera and your bit depth.

My story.

Ive always been 'ETTR' in stills.. but then (after fiddling with an Alexa) I realised that when I ETTR with my Nikon stills cam shooting raw Im actually only ETTR on the histogram which is, I think, generated by the in camera jpg - when I take the NEF file into capture one I still have two stops of headroom.. I must otherwise the exposure slider would not work.

So actually Ive been doing ETTR minus 2 for many years in stills, or maybe ETTR minus 1 because I always shoot a light/right jpg and will darken the file in C1.

But the Alexa/Sony waveform is not got some hidden stuff like the nikon raw histogram.. and that is where I realised (after a long chat with some high end DPs) that to back it off a little with a motion camera is the right thing to do. It would replicate what ive done in stills for years

But stills camera raw have 14bits which is 16000 tones per channel - which is a big heap.

Now you probably know the bits per stop in linear raw..

Stop, Data needed to render it properly.
1   1
2   2
3   4
4   8
5   16
6   32
7   64
8   128
9   256
10   512
11   1024
12   2048

Total 4096.

So you need to render 12 stops properly 4082 levels.. which is a 12 bit camera (red arri canonC300ii, maybe BMC)

So with these cameras ETTR would seem to be the correct thing to do.

But if you are a little poorer and only have a 10bit camera then the codec only has 1024 levels to play with

So maybe sony allocate the available 1024 levels like this.. (a guess)
1   1
2   2
3   4
4   8
5   16
6   32
7   64
8   128
9   128
10   256
11   256
12   256
Total   1151

Here you can see that they do not have enough data to give to the highlights the full tonal rendering they require.

So what is going on? Well you could choose a profile (not Slog) that doesnt record so many stops or if you are doing Slog then you know that the last couple of stops are a bit 'weak' (not enough tones)

So with the sony FS7 in Slog3 I expose 'right' but try and keep 'important' stuff (skin highlights) outside of the last two stops which are 'weak'.

Even poorer? 8 bit camera? (256 tones!)

Clearly you have no way of representing 12 stops with 256 tones.

So if you have an A7s and think Slog will work you need a lobotomy.

Any 8bit camera can only do about 6 stops - so you need a six stop profile usually 'standard' and you expose on the button because you are not going to be able to go any where in post.

In summary..
12+ bits, ETTR
10 bits ETTR with 'important stuff not in the top two stops
8 bits - nail it in camera and avoid 'faux log' settings.

IMO








« Last Edit: January 30, 2016, 01:43:49 pm by Morgan_Moore »
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Sam Morgan Moore Bristol UK

Morgan_Moore

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Re: ETTR, Zebras, zone system etc...in video
« Reply #9 on: January 30, 2016, 01:55:59 pm »

Some random anecdotal notes..

I still try and expose so I am only going to darken in post.

With the Canon 8-10bit cameras you are probably best to use a standard setting or 'wide DR' but not C-log you get less DR but more tonality and grade-ability

With the Sony cameras Slog is sexy and the other settings are horrid so even though another setting might be logical it is not in practice.

With the Sony F5 the SR444 codec is very noticeably much better than XAVC (at 12 bits and 4X the data rate - but the data rate is so high you nearly at the budget point of shooting sony Raw?)

With DSLRs - go home - or get a look in camera

BMC - when I tested raw (2014) is seemed a little odd and not much better than pro-res at a huge cost in data load.

S


 
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Sam Morgan Moore Bristol UK

fredjeang2

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Re: ETTR, Zebras, zone system etc...in video
« Reply #10 on: January 30, 2016, 02:19:45 pm »

Very nice and usefull imputs there. Thanks guys.
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