Getting that S-Log exposure
 

Here is another spot shot using S-Log going to a PIX240. Still getting the exposure figured out. The next spot that I am editing right now should be better yet.

For this spot I more or less used the zebra's for exposure. This was before I learned the method of using my zebra's to expose skin at 70% and then backing down one or two stops or by setting my white at 90%-100% and then backing down one or two stops.

The next spot I post will have those setting used. But for now here is this spot.

Re: Getting that S-Log exposure
 

That looks really nice. I just shot a Harley Davidson spot and used the spot exposure to set grey card (or skintones in some shots) to 38%, with zebras at 100, histogram centered or to the left if highlights deemed it so.. Seemed to work nicely in the grade.

Re: Getting that S-Log exposure
 

Zebras are a poor way to determine exposure, a far more accurate in-camera method is using marker function built into F3 and aiming at skin area to see what you have, or grey card as suggested by other poster. For Slog, 30-40 produces nice results from what I've seen. Without Slog I'm keeping skin around 50 or lower.

I actually only use a light meter now to determine and set my exposure to get consistent results.

Re: Getting that S-Log exposure
 

I disagree, Zebras are great way to judge exposure when used properly -- particulary on bright white or an 18% gray card because those surfaces are consistent and you can know EXACTLTY where the zebras should appear. But using skin tone to judge exposure is always a bad idea because everyone's skin shade is different. Would you put Obama and Romney at the same exposure? Obviously not, that's why judging anything by skin tone just means you're making an educated guess. But white and gray -- those are conistent and zebras can be every bit as accurate as a waveform monitor when they are used properly.

Re: Getting that S-Log exposure
 

Why would you use zebra strips on a gray card or white paper when the F3 has an amazing built-in marker function that will display the actual IRE value of whatever the marker box is hovering over? This is almost as good as a waveform monitor which can be used to show you exactly what values you have throughout a given scene - not to mention FAR more accurate than using zebras to view the overall exposure of a scene.

Also just using zebras can be subjective ie: just how many lines need to appear to indicate you are at a specific IRE? And once you back down "a bit" just how much did you in fact back down, what IRE are you at now? Good luck repeating that from shot to shot or day to day. All that = inconsistency in your shots.

Even if you do manage to use zebras to set your "white" you would still adjust your IRIS or LIGHTING accordingly to the skin level of your subject in the scene, same as you might open up if you are shooting in a dark room with black walls and you want to add detail to the shadows in the shot. Overall "good" exposure takes in account what you are shooting, not just what is white and making sure it is set to "100".

And that is the concept behind exposing for "skin" tone, it simply means with lighter or darker subjects you would bring light levels up or down sublty as required.

Re: Getting that S-Log exposure
 

Dennis, you have just made my point because that is my definition of just guessing at the exposure. I prefer to be more scientific than that because I want to nail the exposure perfectly.

Please don't assume that your way of using zebras is the same as my way of using zebras because I would never do what you have described in your last post. After 30 years of using zebras I think I know what I am doing by now.

But if your way works for you, great. There is more than one way to skin a cat. All I am saying is please don't make a misleading statement that "zebras are a poor way to determine exposure", because that is completely false and does a disservice to inexperienced people who may read it. Zebras can be an excellent way of setting exposure if they are used properly -- like any tool.

BTW, if the "marker function" (it's actually called Brightness Display) is so handy, then I wonder why you are only using a light meter now? I have a 758c meter for times when I need to check something, but it is totally useless in a run & gun situation or anytime I have to be moving fast. Zebras, and sometimes the Brightness Display, provide me with much more information than the light meter could ever dream of.

Re: Getting that S-Log exposure
 

Doug, my first comment "zebras are poor way to determine exposure" was in relation to Gregory's post and the method he had described and used. You then came along describing a different method (your method) so I believe we are in fact discussing two different approaches using zebras.

My comment to Gregory was not at all to criticize his work because in fact the final composition looks amazing and I feel it looks absolutely fabulous! (Proof that using zebras on skin method can work!) But as soon as you stop down from 70% zebras on skin you are REALLY just adjusting the levels to what you feel "looks good". Again, that is great, but it can also be pretty ambiguous. So my suggestion is why not take a reading with your light meter, or waveform monitor, or built-in brightness function (I called it marker function stolen from HVX cams) to see what level your skin is at so you can repeat it as needed? In Gregory's case say for example he was at 70% then stopped down a bit and the skin level reading ended up being 50%. That is quite scientific, so why not use that as a reference point going forward from shot to shot if possible?

As for your method, I would be very enlightened if you would describe it in more details since you agree that you wouldn't expose Obama and Romney at the same exposure yet you mention using zebras to set your white source, but no where did you mention how you might adjust your levels according to your actual subject matter? I'm sincerely intrigued. Please explain.

I mentioned use of the marker function/brightness display for those people who have absolutely no intention of using a light meter since I know people are not big fans of them.

Re: Getting that S-Log exposure
 

Dennis, I need to clarify something I wrote yesterday because when I read it tonight is is confusing the way I worded it.

What I wrote: "Would you put Obama and Romney at the same exposure? Obviously not . . ."

What I meant to say was: "Would you expose Romeny and Obama's skin tones at the same place with zebras or a waveform monitor? Obviously not . . ."

I'm sorry my wording was confusing because I would absolutely expose each of their faces exactly the same. All things being equal, if f/2.8 is the right exposure for one of them, then it would be the right exposure for the other. My exposure is determined by incident light, not the lightness or darkness of the subject. That is why judging expsore by skin tone means you're just guessing.

For example, let's say we set up a headshot of the darkest skinned African we could find. And we both agreed that we had exposed the shot perfectly at f/4. Now the African leaves and we replace him with the whitest albino you could imagine. Would you change your exposure? I certainly would not. The lighting is exactly the same so why would I change my exposure?? One subject is supposed to look darker than the other -- because they are darker than the other. If you try to make every face medium gray and mitigate their natural differences, that is wrong.

Another example. Suppose the albino and the African are standing side-by-side in the frame and we agree again that f/4 is the right exposure for the two-shot. Now one of them walks away and only one is left. Would you change the exposure? Not me. The lighting has not changed.

Another example. Suppose we have a shot of a dark blue box sitting on a table top. Now we replace the dark box with a bright yellow box, but everything else about the shot is the same. Would you change your exposure? I would not. The dark box is supposed to look darker than the yellow box -- because it is. But if I was judging me exposure by looking at the zebras or Brightness Level meter on the box -- then I might be tricked into choosing the wrong exposure. I would set me exposure with a white or gray card, and the lightness or darkness of the box would be irrelevant.

The whole idea of exposing for a gray cards (white cards are the same principle) or using an incident light meter is that your exposure is not dependent on WHAT you are shooting. It is dependent on the actual lighting of the scene.

On the other hand, if you judge exposure by looking at skin tone with zebras, the Brightness Level meter, or even waveform monitor, now you are judging your exposure by an a surface of unknown reflectance and have to guess based on how dark or light you think the subject's skin is.

Using zebras, the Brightness Level meter, or a waveform monitor to measure the light hitting gray card or a white card is the same thing as using an incident light meter. You are measuring the lighting of the scene from a known surface, and not guessing based on how dark or light you think the subject should look.

For example, let's say you think skin tone should be exposed at 38%, 50%, 70% or whatever. That values doesn't matter. What matters is that number, whatever is it, can't possibly be correct for both the albino and the African. At least one of them is going to be exposed wrong.

But if I use an 18% gray card or a white card, I can reliably set me exposure because I know precisely how that surface should be lit. Obviously I might want to adjust the exposure for dramatic or creative reasons, but that is not what we are talking about.

If you really want a great illustration of why zebras can't be used for skin tone, get yourself a DSC Cambelles chart and tell me which of the four girls you are going to use as your standard -- yet they all must have the same exposure because they are on a chart.

If you'd like to come to one of my workshops this summer, I'll be happy to demonstrate my methods of setting exposure in person. :-) The next one is on June 28th at AbleCine New York.

Setting up and Shooting Great-Looking Interviews with LED Lights – New York

Re: Getting that S-Log exposure
 

Hi Doug,
I agree with you that zebras are not a magic exposure wand for faces of varying brightness, but I disagree with you on some of your Light Skin / Dark Skin analysis. I often find that the dark skin may need a 'special' light to bring up a little extra detail, or the pale skin may need to be taken down a bit. I find myself adjusting the light level on the subject to get a more pleasing ratio to the background -- I've been doing this since my days in film. When I have extremely light and dark subjects in the same frame, I'm often adding a light, or taking light off with a single or double net.

Re: Getting that S-Log exposure
 

Hi Dave,

I don't disagree with you. I might adjust the lighting for a particular subject too (for all kinds of reasons), but I'd try to keep the overall exposure the same. Like I said, there's more than one way to skin a cat.

Re: Getting that S-Log exposure
 

One problem is that the zebras don't go down far enough to be of any use with S-log and a grey card. White is less useful as it's in the very heavily compressed part of the S-Log curve so exposure is less accurate and more prone to inconsistencies.

For log, this is true as you will be able to adjust the scene for mood etc in post, all you are doing is trying to ensure as much of you scene fits within the dynamic range of the camera, then artistic choices can be made in post. For standard gammas with minimal post, I don't believe this is at all correct because I believe that exposure is equally dependant on what you are shooting as well as the measured light levels. After all you would not want a mid day scene to be exposed with the same brightness range as an evening scene. I would adjust my exposure differently for your dark skin/albino example if I felt it helped the aesthetics of the shot. It has to be remembered that video cameras and monitors have much more limited dynamic ranges than our own visual systems. Say we are in that room with the dark skinned and lighter skinned people, while we observe the room around us at essentially the same exposure because of our large latitude we will easily see both faces against the background. Shoot them with a limited dynamic range camera and it's often beneficial to cheat a bit to avoid the dark face becoming to dark compared to the background and vice-versa.

Re: Getting that S-Log exposure
 

Alister, obviously there are creative reasons why one might want to light a scene darker or lighter than normal. And that is why I wrote in my last post: "Obviously I might want to adjust the exposure for dramatic or creative reasons, . . ."
So we are in agreement on that point, but I don't think that is really what we are discussing here.

If you're going to adjust your exposure differently for the albino vs. African, what are you basing that difference on? I think it just comes down to the fact that you're guessing. Maybe you have enough experience to make a good guess, but it's still guessing. I on the other hand, would not expose differently for those two faces, and I would set the exposure based on a known value and not the tone of their skin. That's all I'm saying, and that 30 years of experience doing it that way, and never grading to "fix it in post", shows that it works.

The point of my original post was to take issue with the ridiculous statement that zebras are are a poor way of determining exposure. I know that statement is wrong -- whether you agree with my particular techniques or not. Zebras are excellent tool for judging exposure if someone knows how to use them properly.

Re: Getting that S-Log exposure
 

It's not guessing any more than when you drive a car and turn the steering wheel to go around the corner. Most people that have driven a car for some time can judge with incredible accuracy how much they need to turn the steering wheel to drive around a corner that they may have never seen before. You could say they are guessing how much to turn the wheel or you could say they are using their skill and judgement in turning the steering wheel. I don't think we drive cars through guesswork, I think we use a learnt skill. Either way the result is a phenomenally accurate end result considering all the variables involved, something that computers find hard to match.

I say that when someone tweaks exposure to improve the look of a shot that they are using skill and judgement which goes beyond mere guessing. Exposure is not a purely technical exercise where "X" scene needs "Y" exposure. It is a creative, expressive exercise that combines both matter of fact technical skill with creative interpretation. If it was a purely technical exercise then every scene in every movie would be exposed in exactly the same way with "X" exposed at "Y" and that would be incredibly boring. When I adjust my exposure to make an image look nicer, it's not a guess, I know it looks nicer.

While typing this a TV ad came on with an actor in a large number of scenes. In almost every scene the exposure of his face is completely different ranging from deep shadow to brilliantly bright. None of them looked incorrect, they each matched to mood of the scene, there was no way you could have done that using zebras on his face. Zebras do work and can be used for gauging exposure when your working with what I would call a classic average scene. But so much of what we do involves scenes that are not your classic average scene. Then how do you expose? Do you guess or use your judgement and skill?

Re: Getting that S-Log exposure
 

In theory I can definitely agree that what is white 100 in a scene to a camera, that anything else placed in its view really is relatively lit the same as you would see it in real life and should not be changed. But, I would still change the lighting (subtly, such as 1/4 stop increments) depending on WHO sat down. It is artistic decision as Alister has put it, and you don't have to - but if you were hired to shoot the BET awards and didn't open up your IRIS in accordance to what your white 100 level was, I guarantee you would be fired for your work. :)

I'm mainly just saying that once you find the lighting or look you like, use your cameras brightness function, a light meter, or waveform monitor to keep the expsoure consistent throughout your shoot. I just believe there are far better tools for doing this than "zebras".

P.S. I do use my zebras to show me what's clipping in a scene though, one last sanity check i do before pressing record.

Re: Getting that S-Log exposure
 

Actually white is an interesting case in point because while the absolute maximum brightness you can show on a screen is 100% (ignoring superwhites for the moment), that does not necessarily meant that you should expose white at 100%. Lets say you have a room with a white wall and a lamp in the middle. Where do you expose the white wall? Certainly not at 100% because the lamp will be invisible against the 100% white wall. In practice, the nominal correct exposure for a white card with standard gammas is 90% to allow for brighter than white objects.

Now if we take that same room and introduce a desk with a sheet of white paper on it, lets imagine that the sheet of paper is registering at 65% on a waveform monitor. In the overall scene it will appear quite grey and dull compared to the brighter white wall. Now if you replace the white walls with black walls what happens? That same piece of paper will appear much brighter because now it is one of the brightest things in the scene. Same exposure, but the paper will appear to have different relative brightnesses. If you were cutting between two shots like this and the paper was your key subject you might find you need to reduce (darken) the exposure of the second darker shot so that the papers relative brightness remains the same. A reflected light meter looking at the scene average would tell you to increase (brighten) the exposure, an incident light meter would tell you to keep the exposure the same, but in order to maintain consistency between shots you would need to stop down a little which goes against everything your meters, zebras or whatever would tell you.

See the attached image. look at the grey squares. What do you see, does the middle grey square appear slightly brighter than the top one? Well it's not it's exactly the same brightness (65%). What about the bottom grey square, it should appear to be roughly the same brightness as the top one, but it isn't, it's considerably darker at only 45% but the different backgrounds alter the way it looks. It's things like this that mean that exposing "x" at "y" won't always work.

Re: Getting that S-Log exposure
 

What's that saying? To each it's own.
I started shooting back in 1974. Needless to say that my foundation was shooting with negative or positive celluloid. I've never worked in the TV industry, so electronic measuring tools were not my forte.
I use zebras only when shooting run and gun and have no time to use a meter to make sure my highlights are not over 105 or maybe to make sure that my skin tones are not blown.
Most cameramen that had their beginnings working with video cameras feel most comfortable when using electronic measuring tools. Me, give me an incident light meter with a flat face and I'll give you precise exposure throughout the scene.
Since I do my own finishing I mostly shoot flat unless I am in the studio where I can control the light ratios to 709 specs.
I'm not trying to say that my way is the only way, I'm just saying that everyone has its own best way to set exposure.

Re: Getting that S-Log exposure
 

To return to the question:

So using a light meter is the way to go for S-Log (or C-Log)?
Just like measure light for photography?

(The Logs look so weird ungraded... lol... it makes me hesitate to use S-Log/C-Log.
Btw, do you grade with the colorwheels to set black, mid and white levels, or do you use curves, because white is quite compressed?)

Re: Getting that S-Log exposure
 

There is not a one tools do it all. You use the tool that you have mastered in the past and adapt it to your shooting and post preferences for this camera.
Like I said, I use an incident light-meter with a flat face disk. I measure the highlight where I want details do the same with the shadow area that I want details and then get a reading of my main object and determine exposure.
That is what I know and it works for me. You have to see what works for you. A meter, zebras, or the marker in the middle of the screen.

Re: Getting that S-Log exposure
 

With my F3 in S-Log mode I am using a 18% grey card at 38 ire as registered by the spot meter in the VF of the F3. This is giving me great base results. I may stray a stop away from that setup but most of the time I shoot for that value and roll. It looks quite dark in the VF but grades out very nicely.

Re: Getting that S-Log exposure
 

Well, for those who are less experienced than the 30 yr vets chiming in on this subject, I'm sure there's a lot of head-scratching going on--quite a few divergent opinions going on in this thread. Complicating things is that we are apparently talking about multiple concepts: how to best expose faces as well as best overall exposure (two different things, because "exposing" a face may be a function of how one lights it, far less passive than simply setting an exposure). Also, there is run and gun shooting, there is shooting for a broadcast look, there is shooting for a dramatic look. All have very different approaches to lighting and what is considered "proper" exposure for skin tone.

I myself use a combination of waveform, false color and calibrated monitor to match between cameras and scenes, but I'm also working from a DIT station which has all of this in simultaneous display. Mostly I'm shooting in the narrative world which has a larger range of skintone exposure than broadcast, but having recently had the experience of shooting a parody of a reality show with a large cast, I had to wrap my head around high-key lighting to duplicate the look.

Even within that world, I was constantly compensating for varying skin tones amongst the cast. My intention was not to place them all at exactly the same value, but to keep them within a given range. On this Doug and I disagree. I would NOT place a very dark-skinned person under the same lighting as a very light skinned person; as that represents a possible variation of up to four stops of reflective reading, I may reduce that range to perhaps two stops (as well as potentially lighting them with different techniques). In other words, I will light the dark-skinned person hotter than a mid-range caucasian, not so much that their skin tone would end up the same tone, but so that the first individual would show detail in their face that might otherwise be lost. Likewise. I will notch it down on a particularly fair individual for the same reason. They will still read as fair, just not luminescent! If they are both in the same shot, I would endeavor to slow down the fair-skinned person via nets or good planning (such as having them positioned on the far side of the key so they receive less light).

As far as light meter goes: mine only comes out these days when I need to recreate the intensity of a given instrument (in the case of a relight between wide shot and close-up, for instance). Contrary to Douglas, I prefer the ball over the flat disc for reading faces, but as always, to each his own.

Re: Getting that S-Log exposure
 

You don't need a lightmeter Walter, but if you want to read about how I am using one with the F3 to expose my images I have posted it in my blog here with samples, and some further details about my process getting exposure here. You can also head over to Abelcine's website and watch Andy's video where he rates the ISO of the F3 and see first hand how to use a grey card and a light meter with your F3 to determine your working exposure. So for example I already know that I need 42 foot candles or F4, to expose my grey card at 50% when my camera is set to 0db, 24fps, 180 degree shutter mode (or 1/48th). I can light my scene before anyone holds a grey card or any talent sits down. I can walk through an alleyway in the afternoon and know how much light is there to get me my grey. Again, grey is just a baseline. Shoot a dark fella then open up a bit. Shooting casper the ghost? Then close down some. Whatever you think looks good in the end.

But forget light meters all together because that will spark a whole other debate about incident vs. reflective metering..., the method Chris Medeco suggested (exposing your grey card at 38%) is also the same as what this guy did on his F3/SLOG production: http://www.dvinfo.net/forum/sony-xdc...-shoot-f3.html which you can do using a waveform monitor or the brightness display (marker function) built right into the F3. The main point I've been trying to stress here is to shoot for consistency so the quality shows in your work.

38% is not a magic number, you can set your middle grey to 30,35,40,45, 60 even.... but where you decide to put your "middle grey" will depend on a few things: 1.) What else is going on in the scene light or contrast-wise that you want to protect? ie. With 13.5 stops of dynamic range you have the choice of shooting 6 stops bellow middle grey and 6.5 above (maybe to get more range in your highs) or 8 stops below middle grey and 4 stops about middle grey - perhaps you are shooting a lower lit scene where the contrast ratio is low to begin with. 2.) The level of your grey will shift based on what you are shooting, whether it be a boat, a person, a room, or just the mood or look you are trying to acheive.

Charles really hit the nail on the head about something and I wish it came up sooner. There is definitely a difference between establishing a "broadcast" look and a cinema look in terms of exposure - perhaps that's where some differences are surfacing here. I worked in TV broadcast in both the studio and ENG as cameraman and it was never really about what IRE the skin was, we exposed for the highlights at 100 and just shot. This resulted in far brighter images (like you see on 6 o'clock news) then the types of images you might see in dramatic type of film work.

Re: Getting that S-Log exposure
 

The big issue most people have when working with log and exposing mid grey at 38 is that when you look at it on a standard monitor without any lookup tables it looks underexposed. The assumption therefore is that it is underexposed or in some way too dark to ever look right, because that's what people used to working with conventional gammas have become programmed to believe over many years from their experience with conventional gammas. So, for confidence you add a lookup table which converts the log to a Rec-709 type gamma and now the image looks brighter, but as it now has to fit within Rec-709 space we have lost either some of our high end or low end so we are no longer seeing the full range of the captured image so highlights may be blown out or blacks may be crushed.
It's important for people to understand the concept of gamma and colour space and how the only way to truly see what a camera (any camera) is capturing is to use a monitor that has the same gamma and colour space. Generally speaking lookup tables don't help as they will be taking a signal with a large range and manipulating it to fit in a small range and when you do that, something has to be discarded. If you were to take an F3 set to S-log and expose mid grey at 38 and show that on one of the nice new Sony E170 series monitors that have S-log gamma and place that next to another F3 with Rec-709 shooting mig grey at 50% and a similar but conventional 709 monitor the lower and mid range exposures would be near identical and the S-log images would not look under exposed or flat. The S-log images however would show an extra 2 stops of dynamic range.

Furthermore it has to be remembered that log is log, it is not linear. Because of its non linear nature less and less brightness information is getting recorded as you go up the brightness range. As our own visual system is tuned to be most accute in the mid ranges this is normally fine provide you expose correctly putting mid tones in the more linear parts of the S-log curve. Start putting faces to high up the S-log curve and it gets progressively harder to get a natural look after grading. This is where I think a lot of people new to log stumble. They don't have the confidence to expose faces at what looks like a couple of stops under where they would with a standard gamma, so they start bringing up the exposure closer to where they would with standard gamma and then have a really hard time getting faces to look natural in the grade. Remember that the nominal S-Log value for white is 68 IRE. Part of the reason for this is that above about 70 IRE the amount of compression being applied by log is getting pretty extreme. While there is some wriggle room to push your exposure above or below the nominal mid grey at 38 it's not as big as you might expect, especially dealing with natural tones and overexposure.

If you do want to shift your middle grey point this is where the EI S-log function and a light meter comes into it's own, it's what it's designed for.

First something to understand about conventional camera gain, dynamic range and latitude. The latitude and sensitivity of the F3 is governed by the latitude and sensitivity of the sensor, which is about 13 stops. Different amounts of gain or different ISO's don't alter the cameras latitude, nor do they alter the actual sensitivity, only the amount of signal amplification. Changing the actual gain or ISO will change the dynamic range. Increasing the camera gain will reduce the dynamic range as something that is 100 IRE at 800 ISO would go into clipping if the actual camera gain was increased by 6db (taking the ISO to 1600) but the darkest object the camera can actually detect remains the same. Dark objects may appear brighter, but there is still a finite limit to how dark an object the camera can actually see.

EI S-log is different (and EI modes on other cameras). Let's consider how it works. In EI S-Log mode the camera always actually outputs at 800 ISO from the A/B outputs. It is assumed that if your working with S-Log you will be recording using an external 10 bit recorder connected to the A/B outputs. 422 is OK, but you really, really need 10 bit for EI S-Log. At 800 ISO you have 6.5 stops of over exposure and 6.5 under when you shoot mid grey at 38 or expose conventionally with a light meter.
Now what happens when you set the camera to EI 1600? Realise that the camera will still output at 800 ISO over the A/B outputs to your external recorder, but also note that 6db gain (1 stop) is added to the monitor output and what you see on the LCD screen, so the monitor out and LCD image get brighter. As the cameras metering systems (zebras, spot meter, histogram) measure the signal on the monitor side these are also now offset by +6db or + 1 stop.
As the camera is set to EI 1600 we set our light meter to 1600 ISO. If we make no change to our lighting the light meter would tell us to stop down by one stop, compared to our original 800 ISO exposure.
Alternately, looking at the camera, when you switch on EI 1600 the picture gets brighter, your mid grey card would also become brighter by one stop, so If we use the cameras spot meter to expose our grey card at 38 again we would need to stop down the iris by one stop to return the grey card to 38 IRE(for the same light levels as we used for 800). So either way, whether exposing with a light meter or exposing using the cameras built in metering, when you go from EI 800 to EI 1600 for the correct exposure (under the same lighting) you would stop down the iris by one stop.
Hope those new to this are still with me at this point!
Because the cameras A/B output is still operating at 800 ISO and you have stopped down by one stop as that what the light meter or camera metering told you to do because they are operating at EI 1600, the A/B output gets darker by one stop. Because you have shifted the actual recorded output down by one stop you have altered you exposure range from the original +/- 6.5 stops to + 7.5 stops, -5.5 stops. So you can see that when working at EI 1600 the dynamic range now becomes + 7.5 stops and -5.5 stops. Go to EI 3200 and the dynamic range becomes +8.5 stops and -4.5 stops.
So EI S-log gives you a great way of shifting your dynamic range while giving you consistent looking exposure and a reasonable approximation of how your noise levels are changing as you shift up and down the dynamic range.
EI S-Log doesn't go below 800 because shifting the dynamic range up the exposure range is less beneficial. Lets pretend you have an EI 400 setting. If you did use it, you would be opening up the iris by one stop, so your range becomes +5.5 and -7.5 stops compared to your mid grey or light metered exposure. So you are working with reduced headroom and you are pushing your mid range up into the more highly compressed part of the curve which is less desirable. I believe this is why the option is not given on the F3.

Re: Getting that S-Log exposure
 

Actually I should have mentioned that 38% is where SONY rates middle grey when in SLOG mode according to their SLOG white paper. So if nothing else, you just want decent and consistent exposure without getting all scientific, and perhaps you can't monitor LUT'd outs and are forced to look at ugly SLOG on a standard monitor - then use your grey card, set your cam of for 38% and be on your way. Here's a SLOG curve taken from Abelcine's video showing where middle grey would sit on a scope:

http://i1119.photobucket.com/albums/...SLOG-curve.jpg

Re: Getting that S-Log exposure
 

Since watching Alister's excellent presentation at NAB (watched online) - I have been using my grey card on at all times when out and about (it's tucked into my back of my trousers!) - and my footage has been looking, in my opinion at least, lovely. I find it much easier to shoot with S-LOG when indoors but I guess this will always be the case. Have a look at this clip, shot using S-LOG.


I think aside from the dynamic range that is gained, the biggest asset of it is how the camera handles and represents skin tones, I think they look fantastic. Editing now is quicker for me as well (using Sony Vegas), as I have about 10 color curves I've put together and I simply choose the curve that looks closest to the 'correct' one, then I just make small adjustments to that.

Thanks for the time you put into the forum Alister.

Sparky

Re: Getting that S-Log exposure
 

How has Slog help on this video?
What was the range from highlights to shadows?
I can see highlights blown and shadows without details.
Is it Vimeo or does it have to treated in a more powerful program like Resolve or Color?

Re: Getting that S-Log exposure
 

One of the things I find with S-Log is that you get very pleasing highlights on faces as opposed to the sometimes glaring highlights that the abrupt knee with standard gamma or rapid compression with cinegamma.

Re: Getting that S-Log exposure
 

Very interesting and informative thread going here.

If everyone reading this thread thinks that it's nervous time exposing the crossover point 18% grey at 38 because the images look underexposed, then just wait until you get a chance to use a 4K Sony F65 camera which recommends setting it at 32 for S-Log 2. Yes, there is an S-Log 2 designed specifically for the F65. It differs quite a bit from the F3 and F35 S-Log 1 because the huge 8K CMOS chip in the F65 can stretch out that exposure so much more.

I for one have just about had it with producers, directors and craft service people who see my S-Log Only monitor and tell me that I'm underexposed on those faces. You should see what S-Log 2 at 32 looks like. I'm planning on banishing LUT's from my sets and insist that the pertinent people LEARN what S-Log is, what it looks like, what it does, and why they should just get over having a picture perfect image on their video village monitors because somehow a gallon of image has just been crammed into a pint container for them. If you know what you are seeing when you are looking at an uncorrected S-Log 1 or 2 image and it is apparent that all of the detail is there, nothing that counts is overexposed or actually underexposed , then why bother trying to look at it any other way? You know it's going to grade out perfectly. The exception would of course be for any specialized look like a bleach bypass, blue moonlight or other looks you are going to use for that scene later can be replicated in a LUT on set, and that's a good use of them. For straight REC709 monitoring, it's a complete waste of time IMHO.

Sorry for the rant, but I've watched so much time, energy and money wasted on tweaking various LUT's on set - time that could have been better spent on rehearsing or lighting or finishing earlier.

Re: Getting that S-Log exposure
 

On the F65 S-log 2 is a LUT! If your shooting 4K the camera records linear raw, there is no gamma. S-log 2 is provided as a LUT on the HDSDI out and viewfinder because without a LUT the image would be mostly black. Even using S-Lg 2 you still need to use the over/under button to see the high and low end of the exposure range.

Re: Getting that S-Log exposure
 

Alister, you are correct that S-Log 2 is a LUT when the camera is recording RAW or RAW LITE, it is in effect though when you are using the F900 or REC709 gamuts to record.

Re: Getting that S-Log exposure
 

Bruce, trying to understand your rant. Are you saying that producers and directors are getting deeply involved/micromanaging your LUT creation? Why are they even seeing the log images to begin with if you are making LUTS on set? And are you suggesting that by "banishing LUTS" you would make everyone view log images, or just straight REC709 all the time?

I have just had very different experiences so I'm trying to wrap my head around what you are describing.

Re: Getting that S-Log exposure
 

Disagree: learning other people to look at S-log. That is a waste of time.
crews keeps changing every production, good luck with that.

Just tell them that they should leave the picture itself to the pro's (rudly said: shut up or sign up for a speed course)

the rest needs 709, specially on crappy tv's etc

Re: Getting that S-Log exposure
 

Charles, first let me say that the F3 footage you posted recently which you shot for Comedy Central has to be some of the very best low light lighting and camera work I've yet seen come out of that camera. Great stuff.

To answer your question, I come from a different time in the film business. A time when a director would stand just off the edge of the set next to the DP and call action then cut - all the time watching the actor's performance with the naked eye and instincts. After the cut call, if he/she were happy with the performance the DP would be consulted. The DP would consult the operator, if all was deemed good, then they would move on. Multiple producers on set were somewhat rare in those days, and it seemed that a lot more work got done because there was no playback - because there was no video village. Today, I can only think of two directors I have watched on set that still do this (although there are probably more) , Danny Boyle and Clint Eastwood. So I have a built in dislike of video assist, but not just for that reason alone. For most of the time of video assist - which would be from the mid-80's to today, a simple video tap in standard definition displayed the film camera's output. This output was in no way a correlation of the ultimate image quality but rather a method of seeing performance and blocking for the director and camera framing for the DP. Unless focus was way off, it was pretty much impossible to determine it on these standard def taps as was lighting subtleties or shadow/highlight details. All video village seemed to be good at was stacking up a lot of useless producer dead weight and a place for lazy directors to sit down and drink espresso all day. Many actors have agreed with me that this has adversely affected their performances over the years as directors tend to be more detached as a result of not viewing their performance with the naked eye and being in close physical proximity. Let's face it, anyone who's been in front of a camera really needs and wants instant feedback and I think viewing performances on a TV set is not the way to do it for a director. For a DP it was a better fit, but only to check things like camera moves and framing/composition. Until HD Cinema cameras like the F900, Alexa and others came along and allowed this viewing to be done in high quality HD where all of the photographic details are clearly visible and correctable instantly, it was just ludicrous to try and judge exposure, focus or performance on standard definition TV sets. So a lot of time and energy has been misspent in this area over the years. Then along came S-Log and the perceived need to instantaneously see the "final image" on set. The analogy I am drawing here is that I see very little difference between making imaging decisions based on an SD film tap image quality and the absolute reliance on an on set generated LUT. Both to me are mostly folly - with the exception of utilizing a LUT to represent a special lighting effect or film stock characteristic.

Now we are looking at a new paradigm where some of these principles are playing out again. Producers and directors are staring at HD monitors displaying LUT representations of potential final viewing images and expecting that these are the exact versions that will be ultimately used. What I get sometimes is "what's wrong with this picture?" in reference to a LUT that is displaying an artifact like a slightly blown highlight or unclear shadow areas that I know are going to resolve just fine because the S-Log image on my DIT's monitor tells me so, but now we have to spend extra time micro tweaking the LUT to satisfy their need for on-set perfection. This in a nutshell is my issue and problem with on set LUT generation.

What I am proposing is that from now on I will be taking a laptop to pre-production meetings with samples of uncorrected S-Log shot(s) and differently corrected LUT(s) of those shots, in order to try and teach the relevant production people why they should learn how to view and understand an S-Log image on their video village HD set and know from that knowledge that everything they get out of that image is reproducible in the post production grade to generate what they ultimately want. To tell them outright that on set LUTs are just a viewing compromise, so learn to see what's in an S-Log image and be happy that even though it's got very little contrast and the color is wonky, it's OK because in that S-Log image we can all see clearly the detail in the clouds, shadows, and mid-tones, and we are able to instantly correct the "negative" if something like exposure, lighting or focus needs it. This way, everyone is on the same image page so to speak, and there aren't two different images on set to confuse anyone. I always have an S-Log image displayed on set, usually at a DIT station or I bring my own monitor to view it.

Maybe this method of working will be accepted and maybe not, but I feel it is worth the effort.

Re: Getting that S-Log exposure
 

Amen to that.
I guess that once you develop a reputation as a DP and you have explained it ahead of time on Pre-production you will mostt likely to get away with it.

Re: Getting that S-Log exposure
 

Bruce:

Thanks on the compliments on my footage. I wouldn't really categorize it as "low-light" in the strict sense of the phrase--I rarely went above 800 ISO and generally kept my stop at 2.8/4 or higher--perhaps you meant "low-key"? In any event, appreciate the nice words.

I hear what you are saying about having your LUT's micromanaged. Mostly I'm curious what kind of shoots you are doing where they are nitpicking the image to that degree--commercials? Perhaps I've just been fortunate to work with producers and directors who do have an understanding of the process and will only question the placement of tones in the broadest sense of the word.

I feel like I would be doing a grave disservice to these folks by making them view a log image, however. The low-con appearance of the image makes it harder to grasp overall--colors are desaturated, faces are darker, there's no snap, by its very nature--it requires a significant mental translation by the viewer to turn it into the movie. Sure, 10 years ago everyone had to put up with the soft, lackluster look and flicker of video taps (which going back further were black and white, and going back further still to the tube era were barely viewable in low light), but we have progressed far beyond that and once the genie is out of the bottle, it's hard to get the sucker back in. More than anything else, I feel like it's much harder to discern expressions and performances within the murk of a log image, and that is a dealbreaker handicap for the director and producer. I just don't see them allowing that, certainly none of the people I work for.

On my end, once the cameras start rolling my DIT and I are keeping a sharp eye out for critical focus and calling in notes to the AC's, another process which is made harder within the log realm due to lesser contrast. We cycle back and forth between log and LUT'ted image while I'm setting exposures and lighting, but once we roll, it remains in the LUT world. If I was on a show that precluded LUT building, I'd still want to view takes on REC709 for the same reason. Viewing log is great to insure that the values are all there but after that, for me it's just not "the movie".

This all said, I can sympathize with your frustrations and wonder how I'd manage it in that situation. Certainly if having to micro-manage fine tweaking of highlights and shadows in the LUT per an overly fussy director is taking your time away from lighting the set, that can't be a good thing.

Re: Getting that S-Log exposure
 

Charles,
I agree with your attitude toward LUT's & log viewing for the producer/Direct. What were you using for your LUT's when you were still shooting with the F3 & sLog?

Re: Getting that S-Log exposure
 

We were building them for each sketch on the HDLink Pro, using the provided Blackmagic software, which was pretty limited plus the post department wasn't able to incorporate them into the dailies workflow, so it was just for onset viewing. This season we are still using HDLinks but now with Pomfort Livegrade and the Avid control surface we can work faster and better, and the looks are being applied to dailies and will carry through to color correction as a reference. That process happens months after we wrap so both the director and I are able to oversee, which is a nice "luxury". I often have to make compromises for time that I know I can fix with power windows later.

Re: Getting that S-Log exposure
 

Yes, I meant low key photography.

I hadn't worked with the anal-retentive agency "creatives" for quite a while and now I remember why. The whole experience just set me off - I'm feeling more reasonable about it all now.

Charles, you make a good point about not being able to clearly see all of the actor's faces detail while viewing a pure S-Log image and I think that it makes sense to give the director the ability to see that clearly. I think a generic out of the camera 709 LUT would do that job adequately without imposing time penalty. I haven't had the luxury of good on-set grading software and manpower to massage the LUT beast to perfection yet. When you can finesse a LUT with those tools on set and really mimic the grading suite in quality, and you are given the time to do it, then OK, give them what they want - they are paying for it. It's just really hard and a painful waste of time and energy to try and satisfy with the camera output LUTs.

There's a cynical old line from the advertising biz which says in effect, when the client gets what he wants, he gets what he deserves.

Re: Getting that S-Log exposure
 

Have any of you tried just simply adjusting the monitor? I've experimented at home and it looked fine as long you know its just an aproximation and you have more lattitude on the final image. It won't allow color adjustment but you can already do that in the Red Blue offset menu and with the new firmware you'll have plenty of adjustment.
One positive is that your monitor waveform will still be showing the accurate sLog .

Re: Getting that S-Log exposure
 

Ah yes, the agency creatives...good times.

I think REC709 is a great alternative when there isn't time to build custom LUT's. The theory being that if looks anywhere decent there, you know you have room to manipulate it any which way down the road.

Certainly in a situation where there is an expectation for the image to be manipulated for clients on set, they should be prepared to pay for this. I can see making THAT pitch ahead of time; showing them the difference between a REC709 output and various LUT's built to order--that capability coming with a price (DIT and appropriate gear). I've stayed away from extensive coloring via camera menus for years, it's such a slow and painful way to do it compared to having a proper setup in a controlled environment with appropriate monitoring and scopes. Certainly we never wait for LUT's on my set--while I'm lighting, the DIT builds a few different looks based on my description and shows them to me at an opportune moment, and then tweaks further based on whatever notes I might have. By the time we roll, we are usually dialed in.

Leonard, I've certainly tweaked monitors over at video village as you describe--in that two year period of intense DSLR activity for instance, especially once the Technicolor setting became available and I didn't have any other way to dial contrast back into the viewing monitor (right at the end of all that I got an HDLink). It works well enough in most instances.

Re: Getting that S-Log exposure
 

Perhaps this is an excellent example of making lemonade from lemons.

It appears that my recent frustrations can be assuaged easily by having the proper tools at hand. I looked at the Pomfort LiveGrade system and was pretty impressed with how simple a system it is. One could easily put a sub $1000 system together for on set LUT generation with it. Minus the color monitor and laptop investment which most people have on set for transfers and viewing anyway, the software is $480, and the Blackmagic HDlink boxes are about the same price. I have two of these HDlinks for 3D work anyway. Getting any DIT or yourself up to speed on this could be a simple undertaking and then you have the ability to show a better image and hopefully send metadata to post that is relevant - and the best part - charge for it.

Amazing how clear your mind can be after it stops boiling over.

Charles, what format of metadata from LiveGrade were you using and outputting while shooting the F3? I have been using DaVinci Resolve Lite for my personal footage lately and like the controls and ease of use in grading Sony S-Log footage. I see that LiveGrade outputs to it easily.