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FS5 Exposure and General Exposure in Moody Scenes

exposure Lowlight sony fs5 slog3 log camera ALEXA

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#1 Gabriel Wilson

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Posted 04 June 2017 - 04:26 PM

Looking for some exposure help when shooting moody scenes with the FS5 - I have seen a lot of people recommending setting the zebra to 70 percent ( which makes things pretty bright on the monitor for a darker scene/ is this something people only do in LOG? ) are there any other usable on camera exposure tool other than zebra?. Don't use Sony's much and am more used to Using a REC 709 LUT or false colors within my ALEXA eyepiece to expose. Also, should I be switching from LOG3 to cine gamma for lower light situations?  Also any general tips for exposing low light scenes without crushing the blacks?


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#2 Mark Kenfield

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Posted 04 June 2017 - 05:43 PM

Middle grey on SLOG3 is supposed to be 41 IRE. Use a light meter, waveform or false colour to expose to that, and you'llbe fine.
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#3 Robin R Probyn

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Posted 04 June 2017 - 07:00 PM

Zebra at 70 isnt a SLOG 3 setting commonly used AFAIK.. thats more a REC709 skin tone setting more usually.. as Mark said mid grey is around 40%..

 

I dont know about the Fs5, but personally I dont see how anyone shoots with Slog in the EVF..hopefully it has a LUT ..have a feeling it may not.. but has some sort of high contrast VF setting at lest meant to mimic 709 or close to it..

 

Slog is linear in the high lights but dos have a toe/compression in the shadows.. its the opposite of REC709 "mode" you dont have to worry about high lights being saved.. but shadow is the problem.. 

 

Basically LOG on any camera is good for dealing with high DR.. if there isnt any .. its not always the best call data distribution wise.. esp with low light scenes.. with F5/55 I would go to one of the Hypergamma setting .. (Cine Gamma Fs5).. very little data in low light with Slog..

 

Be careful with the Fs5.. I cant remember exactly.. but I believe 4K is only 8 bit..!! sort of defeating the purpose in Log.. internal recording anyway .. HD is 10 bit 422 I think.. 

 

If you could move up to an Fs7.. this is much better equipped camera really.. and still incredibly  cheap.. Fs5 is good for what it is or a B camera.. but its sort of boarder line prosumer 


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#4 Gabriel Wilson

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Posted 04 June 2017 - 07:43 PM

Don't usually use the FS5 but have it for free for a few days so can't upgrade.  I can't seem to find any LUT settings.

 

According to Sony....

 

When shooting with S-Log2/3 and RAW, your brightness levels are very different to when shooting with standard gammas. It’s important that you know those levels.

Sony gives the following as the base exposure levels for S-Log2/3:

S-Log2 is exposed with middle grey at 32% and white at 59% (skintones 45-50%).
S-Log3 is exposed with middle grey at 41% and white at 61%. (skintone 47-52%).


However, when shooting with almost any log camera it’s desirable to shoot a little brighter than the base exposure levels. Shooting log brighter by between 1 and 2 stops is normal practice in movie and TV commercial production and the FS5 is no different. Unlike standard gamma, which do not work well when over exposed, log gammas actually work best when exposed brightly. You are better off being over exposed rather than underexposed.

From experience, I have found that I get the best results in most situations by shooting between 1 and 1.5 stops brighter than the base levels. So I recommend that you use the following exposure levels for both S-Log2 and S-Log3:

Middle Grey: 48-52%
Skin Tone: 56 – 62%
White: 68 – 72%

 

A simple way to get these brightness levels is to set the cameras zebras to 70% and then to expose a white piece of paper so that zebras are just starting to appear on the paper. With the latest firmware you can also set zebras to 58% and expose skin tones with a little bit of the zebra pattern across them or if you have a good quality grey card set the zebras to 50%.


Another simple way to expose 1.5 stops (1.5EV) brighter than the base exposure is to make use of an exposure offset and auto exposure. You can do this by turning on auto exposure and going to the camera menu and using the AE Shift function to add an offset of between +1 and +1.5 EV (I suggest setting all controls to manual and just using the auto iris or auto ND function).

Now the camera will expose 1.5 stops brighter than the base settings whenever auto exposure is used. I normally set the camera up for manual exposure and then use the “push auto” iris control button to momentarily set the exposure automatically. This is quick and easy to do and very handy when shooting on the go.

 

 


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#5 Gabriel Wilson

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Posted 04 June 2017 - 07:59 PM

also, do i just set my light meter to the native 3200 ISO for slog3?


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#6 Robin R Probyn

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Posted 04 June 2017 - 10:46 PM

Im sure there is some setting in VF menu I guess.. some sort of Hi Contrast thing for shooting Slog.. rather than a real LUT.. sure Ive read this somewhere re the fs5

 

Yes fair enough its true its better to over expose log and so the 70% zebra would come into place..but having to do checks off a white card all the time who be a pain.. and white in what part of the scene.. personally I have only over exposed Slog by 1 stop.. depends what your shooting of course .. but you do lose 1stop from your high lights.. but in log 1 stop there is still plenty to spare up there.. and it helps your noise levels in the shadows.. but still I think if its just really dark with virtually no DR at all.. and you cant light it up.. no point to shoot Log.. and a curve with more data in the lower end would be better..

 

I would avoid auto exposure like the plague.. 

 

Sorry i dont know if Fs5 has EI mode.. which is the usual way for setting a uniform over exposure.. better check, but the F5/55 Fs7 in Cine EI will always record at the native ISO.. regardless of any settings.. which makes it easy to over expose on purpose.. if the fs5 doesn't have EI mode I'm not sure the best way.. but of course if you set your metre to a lower ISO than the camera, you will be over exposing your footage..if you set metre to 1600 ISO and the camera is native /or set to 3,600.. you'll be over exposing by 1 stop.. if my maths is right..!

 

Hopefully there is someone who has used the camera that can give you more precise info.. 


Edited by Robin R Probyn, 04 June 2017 - 10:52 PM.

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#7 Mark Kenfield

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Posted 05 June 2017 - 01:17 AM

also, do i just set my light meter to the native 3200 ISO for slog3?


Given that with the F5, F55 and FS7 none of the cameras match the sensitivity claimed by Sony, I would STRONGLY suggest testing the camera before rating its sensitivity,

Use a waveform (or customisable false colour) to set a middle grey card to 41 IRE, and use that reference to confirm the sensitivity to rate the camera on your meter.

Once you've got that sorted, you'll have a safe measurement for exposure.

Overexposing log footage is a bad idea, as it pushed the thing that matters most (people's skintones) into the compressed part of the logarithmic curve, which reduces tonality where you want it most.

Properly exposed, the Sonys are exceptionally clean, so I really don't think overexposing is necessary. I think it's the main reason some people have come to associate the cameras with 'plastic' looking skintones.
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#8 Robin R Probyn

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Posted 05 June 2017 - 03:24 AM

But its linear over grey level isnt it.. even before.. there is no compression  above that .. unlike Hyper gamma curves.. REC709 etc.. the compression  is in the toe.. its the opposite of having to save skin tones in compressed parts of the curve.or high lights ...its a straight line..unlike that you found in HG non log  curves..   every stop is an equal amount of data.. 

 

You are only losing 1 stop of highlights rating it half ISO native (what ever you decide that to be) you still have 6 or so over grey which is plenty for most scenes.. and you are logically/mathematically raising the noise level a stop too.. which can help in some situations.. 

 

Ive never found any problem going with Sony,s native ISO either TBH.. and usually just go with that.. but there is no danger for skin tones in log that I know of.. but certainly that will happen with non log curves that have compression in the high lights.. some of the HG that will start around 70%.. which is why its best to under expose the HG a bit.. but log you dont have that worry..


Edited by Robin R Probyn, 05 June 2017 - 03:26 AM.

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#9 Mark Kenfield

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Posted 05 June 2017 - 06:35 AM

I think you've got a couple of those concepts muddled up somewhere Robin. The whole point of log curves is to compress the highlights, because on a linear scale the brightest stop takes up as much of the bit depth as every preceding stop combined. A linear scale doubles with every stop.

It's only on a logarithmic scale that each stop can possess an equivalent (or close to equivalent) amount of data.

If you're recording a linear image, like Sony Raw on the F5, then you can absolutely overexpose (pretty much without consequence) until you reach the clipping point of the sensor. A log image however is very different, and compression kicks in as soon as you get to the highlights.
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#10 Robin R Probyn

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Posted 05 June 2017 - 08:18 AM

ah yes your right..wrong term to use.. but is it not that above grey that every stop has the same amount of data.. (can be drawn as a straight line on some graphs ) ..  unlike say the HG that have a steep/sudden  compression in the high lights.. or the REC 709 curve.. so you still do have alot of data up there .. and can afford to over expose at least by one stop with out any problems..   almost everyone over exposes Log to raise the noise floor and get a cleaner image.. you dont have to protect high lights like HG curves .. its more protecting the shadows .. its the non log curves surely that you have to worry about skin tones when you hit very strong compression suddenly ..   nes par..?


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#11 Mark Kenfield

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Posted 06 June 2017 - 04:14 AM

I'm sure the compression levels on 'regular' rec709 gammas would be much stronger than on a log curve, owing to the much more limited dynamic range they can contain (though, I have zero expertise when it comes to the Hypergammas and matrix adjustments of the broadcast world, so take that with a grain of salt).

For every stop above middle grey to have the same amount of data, you'd need a STEEP log curve to progressively compress each ascending stop of brightness.

And although I agree with you that you absolutely can overexpose a log image (and a log image has much more scope to do so than any Rec709 curve ever possessed), and there are specific incidences where that is the right call to make. My point is that you don't really need to if you have a properly exposed image in the first place. And that you are compromising tonality in lighter skintones if you do so unnecessarily (that's simply the nature of the log curve). 

I think this rampantly widespread practice of purposely overexposing log footage causes more harm than good, and I think the reason it's become so prevalent, is because people have lost a great deal of discipline and technique where exposure is concerned. We have too many people calling exposure off monitors or histograms, and too few using precise tools like lightmeters, waveforms and false colour.


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#12 Robin R Probyn

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Posted 06 June 2017 - 09:20 AM

Yes true sir.. I usually just go with the native ISO..  just to keep life simple.. and its been fine for me in snow and jungles.. but under exposing log can give you grief .. so little data down there.. and plenty in the highlights.. so its very rarely a problem to over expose by a stop.. or even 2.. but can really help by raising the noise floor..as the op had been advised ..

 

The broadcast gammas.. rec709 with a knee is the worst.. a very abrupt onset of strong compression .. the HG,s have no knee and so the compression comes on earlier but more gradually .. these curves are far more likely to give you compressed plastic skin tones if you over expose.... and why is better to slightly under expose them.. protect the highlights that was drummed into us.. a log curve your skin tones are much safer .. there is no roll off shoulder like the HG,s.. same data each stop .. and alot of data in the high lights .. protect the shadows is more the problem 


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