cinematography, Technology

Should I shoot 8 bit UHD or 10 bit HD?

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This comes up so many times, probably because the answer is rarely clear cut.

First lets look at exactly what the difference between an 8 bit and a 10 bit recording is.
Both will have the same dynamic range. Both will have the same contrast. Both will have the same color range. One does not  necessarily have more color or contrast than the other. The only thing you can be sure of is the difference in the number of code values. An 8 bit video recording has a maximum of 235 code values per channel giving 13 million possible tonal values. 10 bit recording has up to 970 code values per channel giving up to 912 million tonal values.
 
There is a lot of talk of 8 bit recordings resulting in banding because there are only 235 luma shades. This is a bit of a half truth. It is true that if you have a monochrome image there would only be 235 steps. But we are normally making colour images so we are typically dealing with 13 million tonal values, not simply 235 luma shades. In addition it is worth remembering that the bulk of our current video distribution and display technologies are 8 bit – 8 bit H264, 8 bit screens etc. There are more and more 10 bit codecs coming along as well as more 10 bit screens, but the vast majority are still 8 bit.
Compression artefacts cause far more banding problems than too few steps in the recording codec. Most codecs use some form of noise reduction to help reduce the amount of data that needs to be encoded and this can result in banding. Many codecs divide the image data into blocks and  the edges of these small blocks can lead to banding and stepping.
 
Of course 10 bit can give you more shades. But then 4K gives you more shades too. So an 8 bit UHD recording can sometimes have more shades than a 10 bit HD recording. How is this possible? If you think about it, in UHD each color object in the scene is sampled with twice as many pixels. Imagine a gradient that spans 4 pixels. In 4K you will have 4 samples and 4 steps. In HD you will only have 2 samples and 2 steps, so the HD image might show a single big step while the 4K may have 4 smaller steps. It all depends on how steep the gradient is and how it falls relative to the pixels. It then also depends on how you will handle the footage in post production.
 
So it is not as clear cut as often made out. For some shots with lots of textures 4K 8 bit might actually give more data for grading than 10 bit HD. In other scenes 10 bit HD might be better.
 
Anyone that is getting “muddy” results in 4K compared to HD is doing something wrong. Going from 8 bit 4K to 10 bit HD should not change the image contrast, brightness or color range. The images shouldn’t really look significantly different. Sure the 10 bit HD recording might show some subtle textures a little better, but then the 8 bit 4K might have more texture resolution.
 
My experience is that both work and both have pro’s and con’s. I started shooting 8 bit S-log when the Sony PMW-F3 was introduced 7 years ago and have always been able to get great results provided you expose well. 10 bit UHD would be preferable, I’m not suggesting otherwise (at least 10 GOOD bits are always preferable), but 8 bit works too. 
Workflow

Can DaVinci Resolve steal the edit market from Adobe and Apple.

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I have been editing with Adobe Premiere since around 1994. I took a rather long break from Premiere between 2001 and 2011 and switched over to Apple and  Final Cut Pro which in many ways used to be very similar to Premiere (I think some of the same software writers were used for FCP as Premiere). My FCP edit stations were always muti-core Mac Towers. The old G5’s first then later on the Intel Towers. Then along came FCP-X. I just didn’t get along with FCP-X when it first came out. I’m still not a huge fan of it now, but will happily concede that FCP-X is a very capable, professional edit platform.

So in 2011 I switch back to Adobe Premiere as my edit platform of choice. Along the way I have also used various versions of Avid’s software, which is another capable platform.

But right now I’m really not happy with Premiere. Over the last couple of years it has become less stable than it used to be. I run it on a MacBook Pro which is a well defined hardware platform, yet I still get stability issues. I’m also experiencing problems with gamma and level shifts that just shouldn’t be there. In addition Premiere is not very good with many long GOP codecs. FCP-X seems to make light work of XAVC-L compared to Premiere. Furthermore Adobe’s Media encoder which once used to be one of the first encoders to get new codecs or features is now lagging behind, Apples Compressor now has the ability to do at he full range of HDR files. Media Compressor can only do HDR10. If you don’t know, it is possible to buy Compressor on it’s own.

Meanwhile DaVinci Resolve has been my grading platform of choice for a few years now. I have always found it much easier to get the results and looks that I want from Resolve than from any edit software – this isn’t really a surprise as after all that’s what Resolve was originally designed for.

DaVinci Resolve a great grading software and it’s edit capabilities are getting better and better.

The last few versions of Resolve have become much faster thanks to some major processing changes under the hood and in addition there has been a huge amount of work on Resolves edit capabilities. It can now be used as a fully featured edit platform. I recently used Resolve to edit some simpler projects that were going to be graded as this way I could stay in the same software for both processes, and you know what it’s a pretty good editor. There are however a few things that I find a bit funky and frustrating in the edit section of Resolve at the moment. Some of that may simply be because I am less familiar with it for editing than I am Premiere.

Anyway, on to my point. Resolve is getting to be a pretty good edit platform and it’s only going to get better. We all know that it’s a really good and very powerful grading platform and with the recent inclusion of the Fairlight audio suite within Resolve it’s pretty good at handling audio too. Given that the free version of Resolve can do all of the edit, sound and grading functions that most people need, why continue to subscribe to Adobe or pay for FCP-X?

With the cost of the latest generations of Apple computers expanding the price gap between them and similar spec Windows machines – as well as the new Macbooks lacking built in ports like HDMI, USB3 that we all use every day (you now have to use adapters and dongles). The  Apple eco system is just not as attractive as it used to be. Resolve is cross platform, so an Mac user can stay with Apple if they wish, or move over to Windows or Linux whenever they want with Resolve. You can even switch platforms mid project if you want. I could start an edit on my MacBook and the do the grade on a PC workstation staying with Resolve through the complete process.

Even if you need the extra features of the full version like very good noise reduction, facial recognition, 4K DCI output or HDR scopes then it’s still good value as it currently only costs $299/£229 which is less than a years subscription to Premiere CC.

But what about the rest of the Adobe Creative suite? Well you don’t have to subscribe to the whole suite. You can just get Photoshop or After Effects. But there are also many alternatives. Again Blackmagic Design have Fusion 9 which is a very impressive VFX package used for many Hollywood movies and like Resolve there is also a free version with a very comprehensive tools set or again for just $299/£229 you get the full version with all it’s retiming tools etc.

Blackmagic Designs Fusion is a very impressive video effects package for Mac and PC.

For a Photoshop replacement you have GIMP which can do almost everything that Photoshop can do. You can even use Photoshop filters within GIMP. The best part is that GIMP is free and works on both Mac’s and PC’s.

So there you have it – It looks like Blackmagic Design are really serious about taking a big chunk of Adobe Premiere’s users. Resolve and Fusion are cross platform so, like Adobe’s products it doesn’t matter whether you want to use a Mac or a PC. But for me the big thing is you own the software. You are not going to be paying out rather a lot of money month on month for something that right now is in my opinion somewhat flakey.

I’m not quite ready to cut my Creative Cloud subscription yet, maybe on the next version of Resolve. But it won’t be long before I do.

PXW-FS5, PXW-FS7, Shooting Tips, Workflow

Use the cameras media check to help ensure you don’t get file problems.

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Any of the Sony cameras that use SxS or XQD cards include a media check and media restore function that is designed to detect any problems with your recording media or the files stored on that media.
However the media check is only normally performed when you insert a card into the camera, it is not done when you eject a card as the camera never knows when you are about to do that.
So my advice is: When you want to remove the card to offload your footage ensure you have a green light next to the card, this means it should be safe to remove. Pop the card out as you would do normally but then re-insert the card and wait for the light to go from red, back to green. Check the LCD/VF for any messages, if there are no messages, take the card out and do your offload as normal.
 
Why? Every time you put an XQD or SxS card into the camera the card and files stored on it are checked for any signs of any issues. If there is a problem the camera will give you a “Restore Media” warning. If you see this warning always select OK and allow the camera to repair whatever the problem is. If you don’t restore the media and you then make a copy from the card, any copy you make will also be corrupt and the files may be inaccessible.
Once the files have been copied from the card it is no longer possible to restore the media.  If there is a problem with the files on the card, the restore can only be done by the camera, before offload. So this simple check that takes just a few seconds can save a whole world of hurt. I wish there was a media check button you could press to force the check, but there isn’t. However this method works.
It’s also worth knowing that Catalyst Browse and the old Media Browser software performs a data integrity check if you directly attach an SxS card or XQD card to the computer and access the card from the software. If a problem is found you will get a message telling you to return the media to the camera and perform a media restore. But if this is some time after the shoot and you don’t have the camera to hand, this can be impossible. Which is why I like to check my media in the camera by re-inserting it back into the camera so that it gets checked for problems before the end of the shoot.
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Checking Log exposure with the Hi and Low Key Function on the PXW-FS7, PMW-F5 and PMW-F55

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First: If there is something you wish to know about please try the search box to search this web site. You should find a search box on the left of every page when using a normal web browser. If you are using a mobile web browser then the search box will appear towards the bottom of each page, you may need to scroll down to find it, but it’s there.

A great function that allows you to check the extreme ends of your log exposure in the CineEI mode is the Hi/Low Key function. It has to be assigned to a button before you can use it, but it provides a very fast way to check what is really going on in your highlights and shadows. You’ll find all you need to know about High and Low key here.

Workshops and Events

Interfoto Video Camp, Oslo, 7-8th March 2018

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There are still spaces at the Interfoto Video Camp in Oslo next week. I will be there on Wednesday to give a presentation on how I use various Sony cameras including the A7s, PXW-Z90 and PXW-FS5 and FS7. In addition I will be talking a bit about HDR and how I shoot the Northern Lights. In the evening I’m going to give a talk on my career, how I got started, some of the things that help me get to where I am today and where I plan on going from here.

As well as myself there are many other speakers with presentations on all kinds of topics from video production and sound to streaming and gimbals. For more details please click here.

PMW-F55, Technology, Venice, Workflow

How can 16 bit X-OCN deliver smaller files than 10 bit XAVC-I?

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Sony’s X-OCN (X–Original Camera Negative) is a new type of codec from Sony. Currently it is only available via the R7 recorder which can be attached to a Sony PMW-F5, F55 or the new Venice cinema camera.

It is a truly remarkable codec that brings the kind of flexibility normally only available with 16 bit linear raw files but with a files size that is smaller than many conventional high end video formats.

Currently there are two variations of X-OCN.

X-OCN ST is the standard version and then X-OCN LT is the “light” version. Both are 16 bit and both contain 16 bit data based directly on what comes off the cameras sensor. The LT version is barely distinguishable for a 16 bit linear raw recording and the ST version “visually lossless”. Having that sensor data in post production allows you to manipulate the footage over a far greater range than is possible with tradition video files. Traditional video files will already have some form of gamma curve as well as a colour space and white balance baked in. This limits the scope of how far the material can be adjusted and reduces the amount of picture information you have (relative to what comes directly off the sensor) .

Furthermore most traditional video files are 10 bit with a maximum of 1024 code values or levels within the recording. There are some 12 bit codecs but these are still quite rare in video cameras. X-OCN is 16 bit which means that you can have up to 65,536 code values or levels within the recording. That’s a colossal increase in tonal values over traditional recording codecs.

But the thing is that X-OCN LT files are a similar size to Sony’s own XAVC-I (class 480) codec, which is already highly efficient. X-OCN LT is around half the size of the popular 10 bit Apple ProRes HQ codec but offers comparable quality. Even the high quality ST version of X-OCN is smaller than ProRes HQ. So you can have image quality and data levels comparable to Sony’s 16 bit linear raw but in a lightweight, easy to handle 16 bit file that’s smaller than the most commonly used 10 bit version of ProRes.

But how is this even possible? Surely such an amazing 16 bit file should be bigger!

The key to all of this is that the data contained within an X-OCN file is based on the sensors output rather than traditional video.  The cameras that produce the X-OCN material all use bayer sensors. In a traditional video workflow the data from a bayer sensor is first converted from the luminance values that the sensor produces into a YCbCr or RGB signal.

So if the camera has a 4096×2160 bayer sensor in a traditional workflow this pixel level data gets converted to 4096×2160 of Green plus 4096×2160 of Red, plus 4096×2160 of Green (or the same of Y, Cb and Cr). In total you end up with 26 million data points which then need to be compressed using a video codec.

However if we bypass the conversion to a video signal and just store the data that comes directly from the sensor we only need to record a single set of 4096×2160 data points – 8.8 million. This means we only need to store 1/3rd as much data as in a traditional video workflow and it is this huge data saving that is the main reason why it is possible for X-OCN to be smaller than traditional video files while retaining amazing image quality. It’s simply a far more efficient way of recording the data from a bayer camera.

Of course this does mean that the edit or playback computer has to do some extra work because as well as decoding the X-OCN file it has to be converted to a video file, but Sony developed X-OCN to be easy to work with – which it is. Even a modest modern workstation will have no problem working with X-OCN. But the fact that you have that sensor data in the grading suite means you have an amazing degree of flexibility. You can even adjust the way the file is decoded to tailor whether you want more highlight or shadow information in the video file that will created after the X-OCN is decoded.

Why isn’t 16 bit much bigger than 10 bit? Normally a 16 bit file will be bigger than a 10 bit file. But with a video image there are often areas of information that are very similar. Video compression algorithms take advantage of this and instead of recording a value for every pixel will record a single value that represents all of the similar pixels. When you go from 10 bit to 16 bit, while yes, you do have more bits of data to record a greater percentage of the code values will be the same or similar and as a result the codec becomes more efficient. So the files size does increase a bit, but not as much as you might expect.

So, X-OCN, out of the gate, only needs to store 1/3rd of the data points of a similar traditional RGB or YCbCr codec. Increasing the bit depth from the typical 10 bit bit depth of a regular codec to the 16 bits of X-OCN does then increase the amount of data needed to record it. But the use of a clever algorithm to minimise the data needed for those 16 bits means that the end result is a 16 bit file only a bit bigger than XAVC-I but still smaller than ProRes HQ even at it’s highest quality level.

HDR, Workshops and Events

Sony Pro Tour – Oslo, Helsinki and Copenhagen.

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I’ll be giving a seminar on HDR at each of the Sony Pro Tour events in Oslo, Helsinki and Copenhagen.

These are free to attend events where Sony will showcase some of their latest video production products across 4 areas:

Large Format Sensor

Showing PXW-FS7 II, FS7 & FS5

4K HDR Production

Showing PXW-Z90, PXW-Z150 & HXR-NX80 (TBC)

HD Production

Showing PXW-X70, PXW-X200, HXR-NX100

Live Event Production

Showing MCX-500, RM-30BP, HXR-NX5R, SRG-360, RM-IP10 and an RX0.

The Oslo event is on the 8th of March 2018 and the registration link is here.

The Helsinki event is on the 28th of March and the registration link is here.

The Copenhagen event is on the 26th of April and the registration link is here.

cameras, cinematography, PMW-F55, Technology, Venice, Workflow

Sony Venice. Dual ISO’s, 1 stop ND’s and Grading via Metadata.

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With the first of the production Venice cameras now starting to find their way to some very lucky owners it’s time to take a look at some features that are not always well understood, or that perhaps no one has told you about yet.

Dual Native ISO’s: What does this mean?

An electronic camera uses a piece of silicon to convert photons of light into electrons of electricity. The efficiency at doing this is determined by the material used. Then the amount of light that can be captured and thus the sensitivity is determined by the size of the pixels. So, unless you physically change the sensor for one with different sized pixels (which will in the future be possible with Venice) you can’t change the true sensitivity of the camera. All you can do is adjust the electronic parameters.

With most video cameras the ISO is changed by increasing the amount of amplification applied to the signal coming off the sensor. Adding more gain or increasing the amplification will result in a brighter picture. But if you add more amplification/gain then the noise from the sensor is also amplified by the same amount. Make the picture twice as bright and normally the noise doubles.

In addition there is normally an optimum amount of gain where the full range of the signal coming from the sensor will be matched perfectly with the full recording range of the chosen gamma curve. This optimum gain level is what we normally call the “Native ISO”. If you add too much gain the brightest signal from the sensor would be amplified too much and exceed the recording range of the gamma curve. Apply too little gain and your recordings will never reach the optimum level and darker parts of the image may be too dark to be seen.

As a result the Native ISO is where you have the best match of sensor output to gain. Not too much, not too little and hopefully low noise. This is typically also referred to as 0dB gain in an electronic camera and normally there is only 1 gain level where this perfect harmony between sensor, gain and recording range is achieved, this becoming the native ISO.

Side Note: On an electronic camera ISO is an exposure rating, not a sensitivity measurement. Enter the cameras ISO rating into a light meter and you will get the correct exposure. But it doesn’t really tell you how sensitive the camera is as ISO has no allowance for increasing noise levels which will limit the darkest thing a camera can see.

Tweaking the sensor.

However, there are some things we can tweak on the sensor that effect how big the signal coming from the sensor is. The sensors pixels are analog devices. A photon of electricity hits the silicone photo receptor (pixel) and it gets converted into an electron of electricity which is then stored within the structure of the pixel as an analog signal until the pixel is read out by a circuit that converts the analog signal to a digital one, at the same time adding a degree of noise reduction. It’s possible to shift the range that the A to D converter operates over and the amount of noise reduction applied to obtain a different readout range from the sensor. By doing this (and/or other similar techniques, Venice may use some other method) it’s possible to produce a single sensor with more than one native ISO.

A camera with dual ISO’s will have two different operating ranges. One tuned for higher light levels and one tuned for lower light levels. Venice will have two exposure ratings: 500 ISO for brighter scenes and 2500 ISO for shooting when you have less light. With a conventional camera, to go from 500 ISO to 2500 ISO you would need to add just over 12dB of gain and this would increase the noise by a factor of more than 4. However with Venice and it’s dual ISO’s, as we are not adding gain but instead altering the way the sensor is operating the noise difference between 500 ISO and 2500 ISO will be very small.

You will have the same dynamic range at both ISO’s. But you can choose whether to shoot at 500 ISO for super clean images at a sensitivity not that dissimilar to traditional film stocks. This low ISO makes it easy to run lenses at wide apertures for the greatest control over the depth of field. Or you can choose to shoot at the equivalent of 2500 ISO without incurring a big noise penalty.

One of Venice’s key features is that it’s designed to work with Anamorphic lenses. Often Anamorphic lenses are typically not as fast as their spherical counterparts. Furthermore some Anamorphic lenses (particularly vintage lenses) need to be stopped down a little to prevent excessive softness at the edges. So having a second higher ISO rating will make it easier to work with slower lenses or in lower light ranges.

COMBINING DUAL ISO WITH 1 STOP ND’s.

Next it’s worth thinking about how you might want to use the cameras ND filters. Film cameras don’t have built in ND filters. An Arri Alexa does not have built in ND’s. So most cinematographers will work on the basis of a cinema camera having a single recording sensitivity.

The ND filters in Venice provide uniform, full spectrum light attenuation. Sony are incredibly fussy over the materials they use for their ND filters and you can be sure that the filters in Venice do not degrade the image. I was present for the pre-shoot tests for the European demo film and a lot of time was spent testing them. We couldn’t find any issues. If you introduce 1 stop of ND, the camera becomes 1 stop less sensitive to light.  In practice this is no different to having a camera with a sensor 1 stop less sensitive. So the built in ND filters, can if you choose, be used to modify the base sensitivity of the camera in 1 stop increments, up to 8 stops lower.

So with the dual ISO’s and the ND’s combined you have a camera that you can setup to operate at the equivalent of 2 ISO all the way up to 2500 ISO in 1 stop steps (by using 2500 ISO and 500 together you can have approximately half stops steps between 10 ISO and 650 ISO). That’s an impressive range and at no stage are you adding extra gain. There is no other camera on the market that can do this.

On top of all this we do of course still have the ability to alter the Exposure Index of the cameras LUT’s to offset the exposure to move the exposure mid point up and down within the dynamic range. Talking of LUT’s I hope to have some very interesting news about the LUT’s for Venice. I’ve seen a glimpse of the future and I have to say it looks really good!

METADATA GRADING.

The raw and X-OCN material from a Venice camera (and from a PMW-F55 or F5 with the R7 recorder) contains a lot of dynamic metadata. This metadata tells the decoder in your grading software exactly how to handle the linear sensor data stored in the files. It tells your software where in the recorded data range the shadows start and finish, where the mid range sits and where the highlights start and finish. It also informs the software how to decode the colors you have recorded.

I recently spent some time with Sony Europe’s color grading guru Pablo Garcia at the Digital Motion Picture Center in Pinewood. He showed me how you can manipulate this metadata to alter the way the X-OCN is decoded to change the look of the images you bring into the grading suite. Using a beta version of Black Magic’s DaVinci Resolve software, Pablo was able to go into the clips metadata in real time and simply by scrubbing over the metadata settings adjust the shadows, mids and highlights BEFORE the X-OCN was decoded. It was really incredible to see the amount of data that Venice captures in the highlights and shadows. By adjusting the metadata you are tailoring the the way the file is being decoded to suit your own needs and getting the very best video information for the grade. Need more highlight data – you got it. Want to boost the shadows, you can, at the file data level before it’s converted to a traditional video signal.

It’s impressive stuff as you are manipulating the way the 16 bit linear sensor data is decoded rather than a traditional workflow which is to decode the footage to a generic intermediate file and then adjust that. This is just one of the many features that X-OCN from the Sony Venice offers. It’s even more incredible when you consider that a 16 bit linear  X-OCN LT file is similar in size to 10 bit XAVC-I(class 480) and around half the size of Apples 10 bit ProRes HQ.  X-OCN LT looks fantastic and in my opinion grades better than XAVC S-Log. Of course for a high end production you will probably use the regular X-OCN ST codec rather than the LT version, but ST is still smaller than ProRes HQ. What’s more X-OCN is not particularly processor intensive, it’s certainly much easier to work with X-OCN than cDNG. It’s a truly remarkable technology from Sony.

Next week I will be shooting some more test with a Venice camera as we explore the limits of what it can do. I’ll try and get some files for you to play with.