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Canon C300 open house at Visual Impact. Price £9995!

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Crowds gather around the Alexa, F3 and C300

I spent most of the morning at the Visual Impact C300 open house. They had 3 C300’s on show. One on a camera set alongside an F3 and an Alexa, the other was a very simple handheld configuration for people to play with and a 3rd on a stedicam rig.
What impressed me the most was how nice the camera was to hand hold and how good the rear viewfinder is. You certainly don’t need anything extra to shoot with it.
On the camera set I was a little less impressed. At the beginning of the day when I first quickly looked at the 3 monitors I could see no obvious difference between any of the cameras. The monitors were fairly small 20″ Panasonic monitors. However when I went back to take a closer look, for some reason the C300 looked a little soft or not quite in focus. No matter how I played with the focus, the edges of the image looked soft compared to the F3 next to it. Both the F3 and the C300 had Arri 32mm master primes so they should have been similar. I was told all the cameras were set up with standard gammas, but looking at the C300 it looked quite flat, so perhaps it was setup with the Canon Log gamma and the resulting lower contrast was making the image appear softer. There were so many people at the event that it was difficult to really get at the camera to figure out what was going on. I don’t think something was quite right, I’ve seen better from the C300. I asked if I could record some footage but was told that this was not possible on this occasion as these are pre-production cameras. Shame, I had a pocket full of CF cards and SxS cards. Anyway I have been promised a test shoot very soon.

I really hope that the softness was a peculiarity of that particular camera or the way it was set up as the C300 would for me be fantastic for my storm chasing and extreme weather assignments. I’d love to take one up to Norway in January to see if it sensitive enough to shoot the Northern Lights without having to resort to slow shutters or long exposures (Stop Press… I’ve placed an order and hope to have one in time for Norway). I’ve done the math, and according to my calculations it should just about be sensitive enough at 22,000iso with a f1.4 lens to shoot the Aurora in real time. It would be really cool to try and stream the Aurora live from Norway in January. On other assignments I could shoot using Canon L series glass or my B4 to Canon adapter and get broadcast ready material without needing an external recorder. I still think the Sony F3 with S-Log and an external 444 recorder is capable of a better image, but that’s a significantly more expensive package and more cumbersome, power hungry etc. It’s horses for courses. The C300 for me looks to be fantastic for simple, fast, easy shoots where shallow DoF is desirable, while I would continue to use the F3 where the extra bulk of an external recorder and the slightly more complex S-Log workflow will not be an issue as I think the ultimate image quality will be better. I might just have to place an order for one, especially as the price will be less than anticipated. The price I was offered from Visual Impact today was £9995, available from mid January…. Just in time to take to Norway????

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Canon C300 open house at Visual Impact. Price £9995!

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Crowds gather around the Alexa, F3 and C300

I spent most of the morning at the Visual Impact C300 open house. They had 3 C300’s on show. One on a camera set alongside an F3 and an Alexa, the other was a very simple handheld configuration for people to play with and a 3rd on a stedicam rig.
What impressed me the most was how nice the camera was to hand hold and how good the rear viewfinder is. You certainly don’t need anything extra to shoot with it.
On the camera set I was a little less impressed. For some reason the C300 looked a little soft or not quite in focus. No matter how I played with the focus, the edges of the image looked soft compared to the F3 next to it. Both the F3 and the C300 had Arri 32mm master primes so they should have been similar. I was told all the cameras were set up with standard gammas, but looking at the C300 it looked quite flat, so perhaps it was setup with the Canon Log gamma and the resulting lower contrast was making the image appear softer. There were so many people at the event that it was difficult to really get at the camera to figure out what was going on. I asked if I could record some footage but was told that this was not possible on this occasion as these are pre-production cameras. Shame, I had a pocket full of CF cards and SxS cards. Anyway I have been promised a test shoot very soon.

I really hope that the softness was a peculiarity of that particular camera or the way it was set up as the C300 would for me be fantastic for my storm chasing and extreme weather assignments. I’d love to take one up to Norway in January to see if it sensitive enough to shoot the Northern Lights without having to resort to slow shutters or long exposures. I’ve done the math, and according to my calculations it should just about be sensitive enough at 22,000iso with a f1.4 lens to shoot the Aurora in real time. It would be really cool to try and stream the Aurora live from Norway in January. On other assignments I could shoot using Canon L series glass or my B4 to Canon adapter and get broadcast ready material without needing an external recorder. I still think the Sony F3 with S-Log and an external 444 recorder is capable of a better image, but that’s a significantly more expensive package and more cumbersome, power hungry etc. It’s horses for courses. The C300 for me looks to be fantastic for simple, fast, easy shoots where shallow DoF is desirable, while I would continue to use the F3 where the extra bulk of an external recorder and the slightly more complex S-Log workflow will not be an issue as I think the ultimate image quality will be better. I might just have to place an order for one, especially as the price will be less than anticipated. The price I was offered from Visual Impact today was £9995, available from mid January…. Just in time to take to Norway????

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Sony 3D link option for PMW-F3: Quick Look.

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I’ve been playing with the Sony 3D link kit for the F3. I’m still discovering some of the fine details of how and what exactly it gives you, but what I will say right now is that it really, really simplifies 3D with a pair of PMW-F3’s.

The kit comprises of a couple of SxS cards with the software keys required to activate the cameras plus a special cable that connects the two cameras together. After loading the software keys on to both cameras you get an additional menu option to activate the 3D link in one of two modes, master or slave. With one camera connected to the other and one set as master, the other as slave the first thing that happens is that the cameras will sync with each other. My initial testing indicates that this is more than just Genlock, it appears to be full shutter sync. I’ve tried a few fast shutter speeds and so far have not seen anything to suggest the shutters are not in sync, but a proper test is still needed to confirm this.

Other things that happen is that the cameras will both go in and out of record in sync and the timecode of the master camera is used by the slave. If you change the shutter on the master camera the slave also changes. I’m still learning more about the way the 3D link system works and I really like it a lot. Anyone doing a lot of 3D work should seriously consider it. It is pricey at around $5k for the kit for a pair of cameras (although it does also include a couple of SxS cards) but the stable sync, dual start/stop and small things like the sync shutter speed changes does remove another set of things to worry about during your 3D shoot.

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Convergent Design Gemini, one month on.

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I’ve been testing and using a Gemini with my S-log equipped PMW-F3 for a month now and I have to say that every time I use the combo the image quality amazes me.

The Gemini firmware has been updated many times in that month, but I can report that the latest release is nice and stable and delivering the goods. The gemini is remarkable easy to use, the on screen menus are clear and concise. Talking of the screen the LCD is very good indeed. It is clearly visible even in bright direct sunlight. I’ve also been using some other external recorders with screens and the Gemini stands out as a clear winner in this regard.

Power consumption is very good. I’m using Swit 86U batteries with a D-tap to power both the F3 and the Gemini and I get around 2 hours from a fully charged battery. This keeps the size and weight of the rig very manageable, no need to upgrade my tripod or use special mounts for the Gemini, it sits very nicely on the F3’s handle. You can still use the full kit handheld without needing to use a shoulder mount or wear the recorder in a rucksack or similar.

Now.. there are some important things to consider with the Gemini. It is a high end production tool at a low end price. You do get high end, beautiful image quality and you get the same kind of files as you’d use for high end movies and commercials. These DPX files are basically sequences of uncompressed still frames. If you are considering the Gemini you do need to think about your workflow. You will be generating some damn big files, 750GB per hour and that presents a few issues.

Don’t expect to transfer your material to a laptop hard drive in real time. The Gemini uses ultra fast SSD’s because regular hard drives are not fast enough for 444 uncompressed data, so you just won’t get real time uncompressed copies to a laptop drive. It’s taken me up to 3 hours to copy an hour of footage to a fast single hard drive. If you want real time or faster transfers of uncompressed 444 (from ANY device) then your going to want a nice big, fast, raid array, that’s just a fact of uncompressed life.
One option with the Gemini is to convert your files to a compressed codec as you transfer from the SSD’s. This can actually end up faster than doing a straight copy as with a fast computer the material can be pulled of the SSD quickly, encoded and then the more compact file written to a conventional hard drive. For this to be effective I recommend at the very least a dual core i5 2.3Ghz machine. For current model MacBook and iMac users you will be able to use the Sonnet Echo Express thunderbolt to express card adapter along with a Sonnet Express34 to dual eSata adapter to get fast transfers (available December).
I’ve been transcoding to ProRes 4444 and the results are superb. Avid Media Composer 6 now includes a 444 codec but I have not tested this yet. My i7 iMac will encode from uncompressed to ProRes 444 at around realtime speeds.
Another thing you must consider is that because DPX is a stills sequence, there is no audio. At the moment the Gemini does not record audio, so I record both in camera with audio plus the DPX files on the Gemini. It’s pretty straight forward to sync them up in post. There will be a firmware update in the future to add audio recording to the Gemini, so this is just a temporary issue.

So, being realistic about things. The Gemini 444 is a great device. It’s uncompressed so the image quality is fantastic. But you must consider that this is a very high end uncompressed recorder and with any uncompressed HD recorder you will end up with big files. I won’t be using the Gemini for everything I do, the workflow doesn’t suit fast turnaround productions and frankly it’s overkill for web videos etc. But when quality is paramount the Gemini truly excels, performing as well as devices costing many times more, yet offering one of the best LCD’s, very low power and it is a featherweight in comparison to some of the other external brick recorders.

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New Firmware for PMW-F3. EI-Slog and Lens Control

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Sony have posted the latest firmware version for the PMW-F3 on the US web site, click here to go there. This new firmware brings the addition of EI S-Log to those users that have the S-Log option installed. It also adds support for the new Sony servo zoom lens SCLZ18x140. A couple of other improvements include better histogram display and a menu scroll function. Also for S-Log users is the ability to adjust the preset white balance while in S-Log mode.

 

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Red Scarlet-X pricing and specs online now.

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Scarlet-X with Canon mount

So, this comes on the same day as Canon’s C300. Finally we have full specs and pricing on the Red Scarlet X. I have to say I might be ready to jump ship! http://www.red.com/products/scarlet It certainly makes more exciting tech spec reading than the C300. 5K (pixels) sensor, Redcode 4K recording on to SSD’s, 60fps at full HD and a dynamic range of around 13.5 stops.

The price for a ready to go kit is $14k USD which is extremely good for a super 35mm camera with 5K (H-pixels). The use of the Canon EOS mount makes life cheap and simple though the use of L series Canon glass, although a PL mount is also available. The only possible fly in the ointment for me may be a lack of Genlock, which means I can’t use a pair of them for 3D.

Delivery is said to start in December, lets wait and see on that. It’s certainly an exciting time to be a cinematographer with so many interesting choices available. I just wish I could afford one of each.

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New Canon C300 and C300PL cameras and 4k lenses.

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Canon C300 cameras and PL mount lenses

So, I might be a little late on this announcement as I’m currently working in Taiwan, but yesterday Canon released information on two new video cameras and 4 new zooms plus 3 cinematography prime lenses. The press information from Canon is below. Reading between the lines and picking out some of the key points this is a very significant announcement. The cameras have a new 8.29 mega pixel sensor recording to compact flash cards at 1920 x 1080, 4:2:2 at 50Mb/s. The sensor uses a bayer type pattern, but due to the very large pixel count it has a Red and Blue pixel  for each sample in the 1920×1080 frame as well as two Green pixels. This should lead to very good colorimetry, but is a little odd considering that the camera only has a single HDSDi output, which I assume would just be 1.5G 4:2:2, so much of the 4:4:4 data derived from the sensor goes to waste unless it can output 4:4:4 10 bit over HDMI. The higher pixel count and thus smaller pixels than F3/Alexa could have an impact on dynamic range sensitivity and noise, but until I see some raw footage or get my grubby hands on one, who knows? The Laforet video “Mobius” http://vimeo.com/30215350 has quite a “video” look to it, but that might just be the online compression. The camera has a built in Log Curve that is said to offer improved dynamic range. Clearly Canon have some of the F3 market in their sights.

There are HDMI and HDSDi outputs so recording to an external device to improve image quality should not be an issue, 8 bit, 4:2:2 is a bit of a shame on a camera with a sensor spec like this, at least it’s an improvement over the Sony F3’s 8 bit 4:2:0 at 35MB/s. If your going to use the Log curve then you defiantly want to record to a higher quality, preferably 10 bit codec (I am assuming the HDSDi output is 10 bit). UPDATE: I am reading many reports of the HDSDI out only being 8 bit. I hope this is not the case!!!

It does tick many professional feature boxes with XLR audio in, Genlock and even a sync output. This would make it well suited to 3D applications. It looks kind of like a DSLR and has a removable handgrip, a rear mounted EVF as well as a removable smallish LCD panel. One mistake I think Canon have made is that you have to choose between the EOS lens mount and PL mount versions of the camera. Why could they have not made a camera body with a removable mount that would allow you to choose between PL or DSLR glass without having to change the entire camera body, or use an EOS to PL lens adapter with it’s extra optical elements?

Still I do like the thought of a stripped down EOS mount version (C300) with a nice L series zoom on it for shooting on the road or covert filming. However even the use of the EOS mount is a little strange as there is no provision for Auto Focus or Auto Iris, something that you would have thought would be easy to implement. This is a fully manual camera.  I’d really like auto iris you know, if only for tricky time-lapse sequences. Iris control is on the camera body. According to Andy Shipsides of Abel Cine the iris steps slightly as you adjust it when using EOS lenses, what a shame. Makes PL sound like a better option for serious productions.

Having a s35mm sized sensor and the 50Mb/s 4:2:2 codec does meant that it ticks all of the BBC’s approval boxes, so you should be able to use it on most broadcast projects. But it is a strange beast on paper. A DSLR-ish form factor, EOS lens mount without focus or iris control, a 4:4:4 ready sensor but only 4:2:2 recording. Hmmm, you know what, I have to wonder if that sensor isn’t going to appear in another camera with RGB or Dual Link recording. Camera price is approx $20k USD, available in January.

As an F3 owner the new Canon PL mount lenses look ver interesting indeed. The 30-300mm T2.9 – T3.7 would be a great lens for shooting music concerts and other similar events, while the 14.5-60mm T2.5 would be a fantastic all round zoom covering the most commonly used focal lengths that I use.

Canon Press Release:

Lights! Camera! Action! Canon Launches Cinema EOS System

 

All-New Cinema Lens Line-up & Digital Video Camcorders to Leave No Story Untold

Canon today announced its full-fledged entry into the motion picture production industry with the launch of the Cinema EOS System. Canon’s new professional digital cinematography system spans the lens, digital video camcorder and digital SLR camera product categories.

 

The Cinema EOS System targets a new area of imaging and builds on a 74-year history of innovation and expertise in the field of optical and imaging technology.

 

The new Cinema EOS System, offers compatibility with Canon’s wide array of high-performance EF lenses, provides cinematographers with a range of unprecedented creative possibilities to ensure that no story is left untold.

 

With the debut of the Cinema EOS System, Canon today introduced seven new 4K EF Cinema Lenses, four zoom lenses and three single-focal-length models, which complement the current diverse line-up of interchangeable EF lenses for EOS SLR cameras.

 

4K EF Cinema Lens Line up

The seven new 4K EF Cinema Lens models include  four zoom lenses covering a wide zoom range from 14.5 mm to 300 mm, two models each for EF and PL lens mounts, and three single-focal-length lenses for EF mounts.   All seven new lenses deliver exceptional 4K (4096 x 2160 pixels) optical performance and offer compatibility with Super 35 mm-equivalent sensors.

 

EOS C300/C300 PL Interchangeable-Lens Digital Video Camcorder

The Canon EOS C300/C300 PL is an all new digital video camcorder available in two models: the EOS C300, equipped with an EF lens mount which is compatibility with the wide array of Canon EF interchangeable lenses; and the EOS C300 PL, offering a PL lens mount for use with industry-standard PL lenses. The camcorder features a Super 35 mm, 8.29-megapixel CMOS sensor ideally suited for digital cinematography. 

 

Cinema EOS System: Product Overview

7 New EF Cinema lenses:

CN-E14.5–60mm T2.6 L S – (EF Mount)

CN-E14.5–60mm T2.6 L SP – (PL Mount)

CN-E30–300mm T2.95–3.7 L S – (EF Mount)

CN-E30–300mm T2.95–3.7 L SP – (PL Mount)

CN-E24mm T1.5 L F – (EF Mount)  

CN-E50mm T1.3 L F – (EF Mount)

CN-E85mm T1.3 L F – (EF Mount)

 

2 New Digital Video Camcorders:

EOS C300 – (EF Mount)

EOSC300 PL – (PL Mount)


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Picture Profiles – Scene Files – Crispeneing. How to clean up your image.

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I promised I would re-visit some of my Picture Profile stuff. I thought I would start with this one as it is one of the least well understood settings. It’s effects are quite subtle, but it can mean the difference between a noisy picture and a clean image, but also between a sharp image and a soft image, in particular in areas of subtle detail or low contrast detail such as foliage, grass and textures.

Crispening is a part of the detail correction circuit. It does not in itself, as it’s name suggests (at least on an EX of F3) make the image “crisper”. What it does is control the contrast range over which the detail circuit operates. Basically it sets the threshold at which detail correction is applied to the image, which in turn can make the image look a little sharper or less sharp. The apparent sharpness itself is controlled by the Detail Level and Frequency controls.

Why is this useful? Well it allows the user to choose whether to opt for a cleaner looking image or a sharper looking image. An important consideration is that this adjustment does not change the actual resolution of the image or the noise level of the camera, but it does make subtle details in the image more or less enhanced and as noise is also a subtle, even if unwanted detail within the image it will also make noise more or less enhanced, thus more or less visible.

Imaginary waveform showing real picture information plus noise.

In the first illustration I have drawn an imaginary video waveform signal coming from the camera that contains a mixture of noise and both subtle and more obvious picture information. The bigger the up/down change in the waveform the more obvious the change in brightness (and thus contrast) on the monitor or TV would be. Throughout the image there is some noise. I have indicated the noise level for the camera with a pair of red lines. The EX1 and EX3 is a moderately noisy camera, not the worst, nor the best for an HD camera, but pretty good in it’s price range. So if we can do something to make the noise less obvious that would be desirable in many cases. Crispening can help us do that. Crispening ONLY has an effect when you are applying detail correction to the image. It sets the threshold at which detail correction is applied. The default setting on an EX is zero.

Crispening threshold set to -60 indicated by green lines.If we reduce the crispening setting, lets say to -60, it REDUCES the threshold at which detail is applied which generally makes the pictures look sharper. Looking at the second and third illustrations you can see how if you reduce the threshold too much then detail correction will be applied to even the most subtle changes in the image, including the image noise. The little black spikes I have added to the diagram illustrate the way the detail “enhancement” will be added to both noise and subtle contrast changes as well as larger contrast changes.

Black spikes represent detail correction being added to real picture information and noise when crisping set to -60.

This will make the pictures look more noisy, but… and this is important… it will also help bring out subtle low contrast textures in foliage, skin, fabrics etc. A area where perhaps the EX1 and EX3 don’t do terribly well.

If you want a clean image however where noise is less visible, then raising the crispening level to a high positive value, lets say +60 will increase the threshold at which detail correction is added, so signal changes will need to be bigger before detail correction is applied.

Much higher crisping threshold when set to +60

With a high positive number the image will look cleaner and less noisy, but you will loose some enhancement in textures and low contrast areas as these will no longer have detail correction applied to them. This can lead to a slightly muddy or textureless look to tress, grass, skin and fabric.

The real problem areas are the subtle textures and low contrast areas (circled in orange) where the true image detail is barely above the noise level. It’s very difficult to bring these out without increasing the appearance of noise. With Crispening at +60 detail correction is only applied to larger brightness or contrast changes within the image, so noise becomes less obvious.Unfortunately there is no clear answer to how to set the crispening level as it will depend on what you are shooting and how much noise you can tolerate. I tend to have crisping set between +10 and +30 for most things as I do tend to do a fair amount of grading work on my footage. When you grade noise is often the limiting factor as to how far you can push the image, so I like to keep noise under control as much as possible. For green screen and chroma key work I push crispening up to +40 to +60 as this helps me get a cleaner key, especially around subtle edges and hair.

Problem areas circled, subtle textures get lost if detail level set too high, although image looks much cleaner.

If I am shooting exteriors and scenics with lots of foliage, grass etc then I will sometimes go down to -30 as this helps bring out the subtle textures in the leaves and plants, but this can make noise a little more pronounced, so it’s a trade off. And that’s what Crispening is all about, trading off subtle textures and detail against more visible noise. Ultimately only you can make the choice as to which is more important, but the Crispening level control gives you that choice.

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Travel Show shot with F3 wins outstanding Cinematography Emmy!

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The Travel Channel show Anthony Bourdain: No Reservations – Haiti has won an Emmy for outstanding Cinematography. The award is shared by Zach Zamboni, Director of Photography and Todd Liebler,Director of Photography. According to my sources the show was shot using a Sony PMW-F3, so congratulations to them. If anyone finds a clip I’d love to see it. The F3 has to be one of my all time favourite cameras, I really enjoy shooting with it as it puts the creativity lost on small sensor cameras back into the hands of the operator.

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Exposing when shooting S-Log.

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The question over whether to deliberately underexpose or not with S-Log came up recently. I believe that you need to evaluate the entire scene when shooting S-Log and that the often heard “underexpose by a stop” methodology may have some issues. Here’s my take on the situation:

A couple of caveat’s first: Most of my F3 S-Log work has been in indoor situations as I have been tied to recording to various less than portable 10 bit recording solutions, so very often using a restricted contrast range. I’ve only owned S-Log for my F3’s for a short while now, so many of my earlier tests were on 3rd party cameras, some of these were beta cameras.

I have not fully tied down my workflow. I’m still investigating external recorders, everything from the Ninja, Ki-Pro, Sound Devices and of course Gemini. I’m leaning very heavily towards the Gemini as I do a lot of 3D and the Gemini LCD makes for a fantastic monitor.
Back to exposure, this is obviously going to be a slightly contentious area as there is no real “correct way to do it”. While I might not agree with pinning skin tones or anything else for that matter to one particular brightness range, that does not mean I’m right and anyone else is wrong, it is just a different approach and methodology. At the end of the day, if it works for you and gets the results you want, then that will be the way you should go, these things are not black and white, right or wrong.
A very un-scientific test that a did a while back was an eye opener for me. I was exploring the finite latitude of S-Log compared to the F3’s cinegammas. I did a couple of very quick shots, you will find them here: http://www.xdcam-user.com/2011/06/pmw-f3-s-log-and-cinegamma-quick-look/
When I filmed these two examples I was looking at dynamic range, I exposed in both cases with the bright whites of the back wall behind the girl just going into clipping so I could then see how far into the shadows I could still see useable detail. I was not concerned about getting the skin tone exposure correct. When you look at the raw S-Log it really looks pretty shocking and even I wasn’t sure how much I would recover from the highlights and the girl is a good stop overexposed. However after a very simple grade using only the colour corrector in FCP, I was able to extract a pretty good looking image and it’s amazing how much detail was actually retained in what looked like over exposed high lights.  The Girl’s skin tones which I’ve measured at over 85IRE came down very nicely without any issue. A proper grade in a grading suite would I’m sure improve them still further.
What this very crude test told me was that you have incredible flexibility over where you put skin tones, you can comfortably move them up and down in post by a quite significant margin. Also seemingly overexposed S-Log highlights will contain surprisingly large amounts of fully recoverable detail. In the same test I graded the Cinegamma material to try to recover the shadow detail that was lost by due to the reduced latitude. This involved attempting to pull up the shadow areas. While this was somewhat successful, what became very apparent was the way the noise increased quite dramatically, this is something I have been aware of since I started using Cinegammas many years ago, pulling levels up will increase noise.
So… when I expose with Cinegammas (as I have done for many years) I have always been very conscious of the noticeable effect on noise that trying to lift underexposed parts of the image has. Very often in the grade the limiting factor as to how far you can push the image has been down to the noise floor and noise effects. This has mainly been with Sony EX’s which have a 54db noise floor.
Now with the F3 with have a dilemma! S-Log gives us another +1.5ish stops of dynamic range, but at the expense of a +6db increase in noise due to the +1 stop increase in sensitivity associated with S-Log.
Lets say for example that we shoot a shot with a person and we under expose the face by one stop (one stop = 6db).
If we do this with with the Cinegammas and then grade the shot bringing the face up one stop then the noise will increase by 6db from the base noise figure of 63db giving a final noise figure of approx 57db (in the case of signal to noise, a lower number is worse).
If we do this with S-Log and then grade the shot bringing up the face by one stop then the noise will increase by 6db from the base of 57db giving a final noise figure of approx 51db.
So the S-Log image becomes twice as noisy as the cinegamma material and therefore depending on the footage, it is quite possible that you would actually be able to push mid ranges and shadows further with Cinegammas than S-log in an underexposed situation due to noise issues. The S-Log and Cinegamma curves are almost identical up to over 50IRE, so latitude performance under 50IRE is essentially the same. See the charts on this page: http://www.xdcam-user.com/2011/05/s-log-a-further-in-depth-look/
If I get some time at IBC I might see if I can set up some tests to show this in practice.
Now given that I have seen for myself how with S-Log skin tones can be pushed down just as much as up in post, I tend to try to evaluate the entire scene and consider how it will be treated in post before choosing how to expose. In particular I don’t want to expose so that the entire scene will end up being lifted by a significant amount, as noise will become a concern. This isn’t always going to be possible as there are many shots where highlights have to be protected, but I don’t believe that you have to set skins etc at any particular narrow brightness range, I tend to let skin ride somewhere between 45IRE and 70IRE depending on the overall scene.
If I can fit the contrast range of the scene into the 11.5 stops of a cinegamma then I will often use the cinegammas over S-Log because of the noise improvement. S-Log comes into it’s own where you have an extreme contrast range that needs to be captured. However at the end of the day you do still have to remember that the end display device is unlikely to be able to display more than 7 stops with any accuracy!
One tool I have found very useful is the BlackMagic HDLink box. I often use this to connect to a monitor as it has the ability to apply LUT’s very quickly. If you have a PC connected to the HDLink you can go in an modify the LUT curve in real time and in effect do an on-set grade. The HDLink is only $499 USD.