RAW S-Log Clip to Download

[Douglas Villalba]

Thinking of getting an F3 and want to get your hands some S-Log un graded footage? Here is your chance download this ProRes HQ 10 bit clip SLog NOT GRADED.mov

Here is Apple Color Graded version SLog GRADED COLOR.mov

Enjoy

[Koravik Rakpetchmanee]

Nice one. what lens did u use?
cheers.

[Alister Chapman]

How did you set your exposure Douglas? It looks just a little over exposed to me, mid grey should be 38% and white 68%. Over exposure effects the linearity of the mid tones and highlights which makes it harder to grade.

[Douglas Villalba]

Originally Posted by Koravik Rakpetchmanee

Nice one. what lens did u use?
cheers.

Hi Koravik. I used the never used on a paid job Tokina 11-16mm f2,8

Originally Posted by Alister Chapman

How did you set your exposure Douglas? It looks just a little over exposed to me, mid grey should be 38% and white 68%. Over exposure effects the linearity of the mid tones and highlights which makes it harder to grade.

Hi Alister. I used my trusty light meter of about 20 years with a flat surface (not the dome). The dome is for average light setting and that is why people change the ISO rating. Wrong tool.
I measure direct sun light (highs) and under the shade (lows) facing where the reflected light was coming from. Then I split the difference and set my lens to that. I this case since the ratios were about 6 f-stops and I have no absolute way of determining f-stop on the Tokina I used the VF to set the iris +- to my meter reading.
As I told you on your xdcam-user.com forum, I don't use charts or waveforms for production, but I use scopes on post and everything is within 0-100 IREs. I can set my highlights, middle and lows where ever I want in post, I just like my white clouds to be white with detail.
As far as mid gray at 38% and whites at 68% since I don't use the waveform or the meter in the camera, I can't tell you I if agree or not with those finding. What I have found on my testing is that I like the way I can correct or improve over exposure better than I can under exposure.
See the simple test I did just opening and closing the Iris one stop at a time 14 f-stops.

Sony PMW F3 S-Log Usable F-Stops Test on Vimeo

[Alister Chapman]

The problem with S-log is that it is log. So while you do get a greater dynamic range to play with, correct exposure becomes more critical than with a standard gamma. With a standard gamma, which can be considered as "near linear" it really doesn't matter where you place your picture information provided it is neither overexposed or under exposed as all parts of the range can be considered equal. With S-log (and Cinegammas and Hypergammas to a lesser degree) the higher up the exposure range you go, the more compression gets applied to the image prior to recording. As a result brighter parts of the image are more compressed than darker parts and contain less brightness and contrast information. Typically this isn't an issue as our own visual system is tuned to mid tones, faces etc and we tend not to notice anomalies in the brighter parts of a scene.
However when you start grading your image if you are over exposed you'll find it much harder to recover the best possible image. You want to expose so that those important mid tones are within the more linear part of the exposure range which is below 50%. Typically faces, plants, foliage etc should be below 50-60%. White should be around 65-70%. This then gives you a generous overexposure range to cope with direct light sources such as the sky, clouds and reflections. It's not really good enough to simply keep everything between 0-100%, you need to carefully manage your mid tones and place them in the S-log sweet spot.

It's really, really easy to use a grey card with an F3. Simply use the F3's spot meter to measure the exposure. Much faster and more accurate than a light meter. Grey cards cost very little. If you don't have a grey card then a white card at 68% will be very close. These numbers were not simply grabbed from thin air. They are the design parameters for the S-Log curve and correspond to the LUT's and gain settings used in most grading suites. I strongly recommend that you use them for S-log.

A face exposed correctly at around 40-50% will have considerably more subtle texture information than a face recorded at 65-70% where the extra compression due to the logarithmic signal reduction reduces the amount of data required to record each successive stop. S-Log does not behave like film, nor is it like a standard gamma curve. In many respects it is the opposite to film. With log your most useful part of the exposure range is the low range, this is where your best detail and contrast will be so you need to make the most of it by exposing accordingly. With film, if anything you would favour a slight overexposure rather than under. S-Log is the opposite. Don't expect to be able to see everything that's going on in the shadows correctly on a standard monitor. The gamma miss-match between log and most monitors means that you won't see the full range of subtle tones captured in the low range until you grade or correctly apply a look up table.
There is a lot of miss understanding about the way S-Log works and how to get the best from it. The assumption (incorrect) is that because it has greater dynamic range you can be more relaxed with your exposure, but this is simply not the case. You must be just as careful and you must learn to hit the sweet spot for the best results. It also helps to use a grading tool that supports log gain instead of linear gain. If you grade using tools designed for standard gammas you will get unnecessary noise increases as you adjust the log curve. You must either de-log the clip first and then work in standard gamma space or use the correct log gain setup. If you don't do this your highlights and brighter parts of the image will have a tendency to blow out and become excessively bright whenever you try to lighten the image. I don't know about color but certainly resolve has a specific log mode and the difference is night and day.

[Douglas Villalba]

It sounds so complicated. I don't even have to bring the camera out until I'm ready to shoot.
If you don't understand light meters, use what you do know. A light meter also read a reflexion off of a white disc. The only difference is that it is not affected by things like glare, differences in color, scratches, dirt, etc. I have a Kodak gray/white card,,, somewhere. I use to use it for white balance with cameras that didn't have adjustable Kelvins.

Why would anyone need ISO rating if a waveform doesn't use the ISO for reference only a lightmeter does. A waveform only measures a percentage of reflection within the range that the camera sensor can see and it is affected by the reflectance of the surface being measured.

I haven't seen a video of the 38"/61" theory to see how it holds up when graded. I want to see an open and closing of that iris 14 stops like I did on my test. Theory is good, but what counts is actual footage wish is what I get paid for.

All the tests that I have seen are of a couple f-stops difference and poorly graded right on an NLE.
I used Apple Color because it is a powerful tool that can bring the highs into detail the same as lows without affecting the rest of the image. Just look at my 14 f-stop test split screen before and after simple grading and make you own conclusions.

I'm sticking with my lightmeter. It works for me and my clients like what I do. They can care less what I use or how I use it.

[Alister Chapman]

Sorry, but I don't understand why you would prefer to use a light meter when you can use the cameras built in tools for 100% accurate measurement of the actual recorded image.

In my mind it's like using a dip stick to work out how far the fuel in a car will get you when you have a modern car with a trip computer that will tell you exactly how far you can go. Times change, technology moves on. I'm not convinced your method is working as your clip appears to be rather overexposed. But as you say, it's your choice and if you feel it's working for you then carry on.

[Douglas Villalba]

There is more than one way to skin a cat. I have been getting the results I want my way for over 30 years and it still works for me.

Tell me what you find wrong with the 14 f-stops test I did. It is not theory it is fact.

Everything changes once you do your own grading on a qualified grading tool like Resolve, Apple Color, etc. Adding an S curve plugin to FCP, Premier won't do it.
There is more in the 10 bit highs than what you see on you monitor. The same happens with the lows, but they brake up sooner in grading and looks really noisy and pixelated as you can see in my test.

[Simon Denny]

I know this is a F3 forum but was reading your comments Alister and found them to be in line with my experience in relation with Clog on the C300.

I have been using a Canon C300 in C-log mode and have found getting correct exposure is a bit tricker than at first thought. Skin tones I'm finding need to be exposed lower than I have been doing on the Sony 500.
I'm also finding it's a fine line between under and over exposure in log mode.

[Douglas Villalba]

Originally Posted by Simon Denny

I'm also finding it's a fine line between under and over exposure in log mode.

The whole idea of Log is the wide range of exposure latitude. What do you mean by a fine line between UNDER & OVER?

What that means to me is one f-stop difference between under & over.

[Simon Denny]

Yeah that didn't sound right when I put that down, what I meant was skin exposure to my eye compared to hyper-gamma from a 2/3rd inch camera.

[Alister Chapman]

Log gives us more latitude, but the majority of the extra latitude is in the shadows. But because the images are no longer correctly displayed directly on a standard gamma monitor you can't easily directly see a lot of the extra latitude when you shoot. As a result there is a tendency for many to over expose instead of shifting the exposure range down to take advantage of the increased low end latitude. It's why the EI modes in the F3 only go up in ISO and not down, shifting the exposure range lower down the log curve.

It's only when you go to a camera with 12 or 14 bit linear recording, like the F65 that you can really afford to place your exposure range wherever you want it.

[Douglas Villalba]

We will continue to agree to disagree.

You may have a crystal ball that gives you the Lotto numbers, but you still have to buy the ticket and the numbers have to actually come out.

The only proof you think you have is a scaling gray chart perfectly expose where you say it shows more detail on the dark area of the chart than bright area of the chart. If done that way I will concede since I haven't really checked or care to check.

My concern is actual exposure since that is what we shoot, not a back lit charts.

I specially like how Zacuto did the test in their Camera shootout 2, Minute 4:34. This was a camera comparison and not an F3 under and over comparison but all you needed to do is change f-stop to see how it resolved at different exposures.

Hey what do they know? They were only famous ASC cinematographers conducting the test.

The Great Camera Shootout 2011: Episode 2 ~ "Sensors & Sensitivity" on Vimeo

See what they used to determine exposure at minute 4:03

https://vimeo.com/24334733#

[Alister Chapman]

The method I use to measure dynamic range and latitude using a back lit dynamic range chart and waveform monitor is one of the standard methods for measuring the actual dynamic range and latitude of a video camera. The measurements I make are done in accordance with ISO standards. The same charts can also be used with film. It's very accurate and when done correctly repeatable time and time again. It is not subject to issues such as changes in lens flare with aperture, aperture or ND filter inaccuracies, personal interpretation, monitor issues or other vagaries.

It's almost exactly the same method the Andy at Abel Cine uses. You can view videos about how he does it here:
S-Log and the Sony F3 – Part 1: On the Charts | CineTechnica

And surprise surprise, Andy came up with the same results as I did. If you think we are both wrong, and the majority of other people that have measured and plotted the DR of an F3, then that's up to you, but I stand by my measurements and my advice on how to expose and use S-Log. It's not film, it doesn't behave like film and as a result you should modify the way you use it if you want the best results.

[Douglas Villalba]

Originally Posted by Alister Chapman

The method I use to measure dynamic range and latitude using a back lit dynamic range chart and waveform monitor is one of the standard methods for measuring the actual dynamic range and latitude of a video camera. The measurements I make are done in accordance with ISO standards. The same charts can also be used with film. It's very accurate and when done correctly repeatable time and time again. It is not subject to issues such as changes in lens flare with aperture, aperture or ND filter inaccuracies, personal interpretation, monitor issues or other vagaries.

It's almost exactly the same method the Andy at Abel Cine uses. You can view videos about how he does it here:
S-Log and the Sony F3 – Part 1: On the Charts | CineTechnica

And surprise surprise, Andy came up with the same results as I did. If you think we are both wrong, and the majority of other people that have measured and plotted the DR of an F3, then that's up to you, but I stand by my measurements and my advice on how to expose and use S-Log. It's not film, it doesn't behave like film and as a result you should modify the way you use it if you want the best results.

I am not looking at who is right or who is wrong. I am doing my test my way because that is what I trust.

You don't understand my test, that is fine. I don't think that anyone that uses TV tools will. I didn't post it for or mention you in it. You have taken my test personal for some reason. This test is not intended to proof you right or wrong. Most likely you can arrive to same exposure as me using your tools and me using mine.

All I can tell you is that my test is not 100% useful to everyone else and I heven't seen your test clips, so can't even comment on them.

Anyone else that saw the 14 f-stop test you can do what I do with most of the tests I see. Use what you can and do your own test. If you don't have the camera download my free clip. It is the only free S-Log ProRes HQ 10 bit clip in the internet that I know of that you can download. The camera with and without slog is awesome.