BBC64 camera line-up 'chip-chart'

I'm at the studio build today setting up camera channels and doing general line-up. We've supplied the good-old BBC64 camera chart which I used to spend many happy hours staring at whilst lining-up cameras for studio/OB shoots. When I die (and they lay me to rest....) I want this and Test Card F on my gravestone!
The info sheet has all the reflectance figures and frequency gratings for when you have the camera focused full-frame on the chart.
Oh, does anyone know why the light-trap in the middle of the chart is called a Gregory Hole?
Also - ex-BBC type, can you still get hold of Cardboard Kate?

Demystifying Digital Camera Specifications

April 3, 2008 - John Galt, Head of Advanced Digital Imaging at Panavision, and Larry Thorpe, National Marketing Manager at Canon Broadcast & Communications Division, came together to help untangle some common misunderstandings in Digital Camera Specifications.

One thing that I had never really appreciated was the reason why single sensor cameras produce RAW images and why that is important. Why, I thought, couldn't you just take full-res RGB from the camera (most RGB formats - TIFF and Targa can represent more dynamic range that the sensor can produce) and be done with it? However - a Bayer matrix in front of a single sensor is a heck of a compromise and if you want to stand the best chance of extracting all the resolution (in all three channels) you are stuck with RAW. I suppose having such a background in video means I always think about image capture and processing in terms of RGB.
Mark Lloyd (root6's own webmaster and guerrilla filmmaker) tells me this is proving a thorn in the side for the Red camera which uses a Canon DSLR image sensor (Bayer-filtered, of course).

Anyhow - watch the presentation - the link in the title is to the 480p starting at part six. The final two parts are the most interesting for bayer/single-sensor cameras. The first two parts provide a very good explanation of MTF (Modulation Transfer Function).
If you're hungry for more (and who isn't?!) The Schubin Report had a great podcast on the subject last year.

ITU Rec 601 vs Rec 709 colourspace

Every superhero knows that in transitioning from standard definition television to high def we've adopted a different matrixing function for component to/from RGB conversion. The numbers for (old-skool) Rec 601 are thus;

Y = 0.299R +0.587G +0.114B
Cb = 0.564(B-Y) + 350mV
Cr = 0.713(R-Y) + 350mV

And the new kids on the block (Rec 709);

Y = 0.213R +0.715G +0.072B
Cb = 0.539(B-Y) + 350mV
Cr = 0.635(R-Y) + 350mV

So, not only has the weighting of the colours that make up the luminance path changed but the weighting of the colour difference signals is different. I've heard varying accounts of why they felt the change was necessary - I think it's probably to do with cameras and telecines (now be entirely CCD-based as opposed to the ubiquity of tubes when 601 was being formulated) and display devices (are we going to be able to buy a tube'd monitor by the end of this year?!). The new values better reflect the tri-stimulus nature of human vision and are less bound by the very noisy response of the blue-tube in image acquisition devices of yester-year.

However, one of the upshots of this is that digital devices that can receive an SD/HD-SDi bitstream have to be able to switch in the appropriate matrix. If that isn't the case then you'd notice a green cast on pictures if you switched between standards (going from HD to SD) or a magenta error going the other way. In the case of a monitor you'd have to re-calibrate the white point to D65.

The reason this has cropped up is that a facility (where I've just started to offer them colour calibration advice) has noticed that a monitor that was lined up correctly for HD working is showing the wrong colourimetry when being sent an SD feed. It's gone green (and not with envy! - oh, and that isn't the facility in case you're wondering!). It's a JVC DTV1700 series monitor which (although a cheapie at <£2k) has an EBU-phosphored tube (so you can calibrate it to 6500k at the white point). It looks like JVC's input card doesn't do the matrix switch. So, I'm wondering what other monitors do - I was sure the Sony BVM-D range did (but those monitors started in the mid-teen thousands of pounds). Any comments from people who've hit this before? As an aside the image (right - click it!) is from a very good Tektronix poster entitled Understanding Colors and Gamut - I have many copies (along with the equally exciting Understanding High Definition Video!) - give me a yell if you want one.

Red camera, NAB and vaporware!

Although my star doesn't burn bright enough in the broadcast engineering sky to warrant a trip to Vegas to see the newest things in TV and Film technology there has been a lot of online chatter relating to the Red HD/DI/EFP (whatever?!) camera. It's a >4k res aquisition device and here is the blurb from their website:

Typical high-end HD camcorders have 2.1M pixel sensors and record with 3:1:1 color subsampled video at up to 30fps. We deliver 11.4M pixels at up to 60fps and record RAW, or 2x over-sampled HD in 4:4:4 or 4:2:2 - your choice. That’s more than 5 times the amount of information available every second and a vastly superior recording quality. Don’t need all that data for your workflow? Dial it back, and keep all the other advantages of the Mysterium Super 35mm cine sized (24.4 x 13.7mm) sensor. You get the same breathtaking Depth of Field and selective focus as found in film cameras. Mysterium boasts a greater than 66db Signal to Noise Ratio thanks to its large 29 sq. micron pixels. And 11,480,800 pixels deliver resolution that can only be called Ultra High Definition.

Given that they are proposing selling this gadget for somewhere between a fifth and a tenth of what you'd currently pay for a Viper etc then you have to take notice. Also bear in mind that these guys normally manufacture sunglasses. The argument I've heard is that being an optical company Oakley are well placed for this kind of product but I think it's fair to say that optics aren't the bottleneck in digital cinema cameras at the moment - it's all the stuff encompassed by their "mysterium" sensor and the resultant data-load.
I showed the picture of the camera to my thirteen year-old and his response was "cool"! It looks like a weapon out of Halo - which is why there is such a buzz on the web - the Mac community love it. Never mind that all they are showing is an aluminium mock-up, it looks cool.

I suppose I'll reserve judgement - I hope I'll be suprised but I expect not. It put me in mind of an all encompassing-price bustin' NLE/production system from about ten years ago - the Trinity Play system that showed at IBC/NAB etc. for a couple of years but never shipped (I had one on order for a year!). While I was looking it up on the web I noticed that Kiki Stockhammer (one of their founders) - who used to do a really good demo - is now playing in an LA SciFi punk band called Warp 11 - amazing!

Panasonic's P2 solid-state recording system

Today we had a visit from a couple of product managers from Panasonic - the BBC has committed to their P2 system for DV, standard-def, and high-def acquisition. It is very well engineered with commodity parts. The PCMCIA format card (which has error correction and data striping inside) contains four SD cards - so currently they will sell you an 8 gigabyte one (as well as four) which holds eight minutes of DVCPro HD at 1920x1080 (yes - Panasonic supporting something better than 720 lines!) or half an hour of DV res. It records in native DV codecs (4:1:1 and 4:2:0 supported) wrapping it all with an MXF header. Avid supports it out of the box and they have a cute little play/review app (see the picture above) that means that moments after you've ejected the card from the camera you can be watching or editing natively. It has all the groovy auto meta-data you'd want (including a GPS receiver and cameraman voice-recording) and seems just the right mix of off-the-shelf and innovation.
It's a pity it's all DV-type codecs - 100mBits for HD is kinda bad (compared to HDCam's native data rate of 270mBits). Even against IMX or BetaSX (which are long-GOP formats) it's not going to look better. Still - if the Beeb like it......

"The perils of colour-space conversion" - an article for the Root6 Dr. Watson newsletter

At work we produce a newsletter which I sometimes do a technical piece for - so forgive the slightly client facing tone of this piece!

An important aspect of the production/post-production chain is maintaining correct colourimetry. If the director of photography or the lighting-cameraman want that certain shade of red to be correctly delivered to the viewer then attention needs to be paid to the correct representation from the camera (be it standard or high definition or even film) through all transfer operations (potentially going between resolutions, YUV/RGB colour spaces and bit depths) to the final display surface (be it a CRT, LCD or even cinema screen). In truth colour-space management for film is a complex issue best handled by specialists like Filmlight (who are represented in the UK by Root6) and is perhaps beyond the scope of some technical notes in a newsletter! That said there are many points worth making if you are acquiring or delivering for high definition television and worried about going between colour spaces.

The CIE Chromaticity diagram (first published in 1931!) shows the gamut of human vision – essentially any display surface is a subset of this diagram and will be a triangle with red, green and blue apexes and white (actually monochrome – as the luminance of the image is reduced it tends through grey to black) in the centre. In the case of “illuminant D” (AKA “D6500” or “EBU phosphors”) – the standard definition colour standard used since the sixties in Europe we enjoy a slightly wider red range than our colonial cousins but every gamut (television, film or print) is a poor compromise on what your eyes can handle. This is where the problem begins – you have a very critical instrument at your disposal to see these differences.

Part of the problem is that all of our machines acquire images in the RGB space (TV cameras, Telecines, graphics workstations etc.) but for the most part we post-produce in a YUV space (with the exception of Sony’s new HDCam SR format, an RGB high-definition VTR) which represents an immediate lowering of the colour space. This has been the case for a long time and is well understood. Manufacturers have agreed a common “matrix” for transcoding. To make the luminance portion of the component signal the following is used:

y = 0.299 * r + 0.587 * g + 0.114 * b

Well, this is the case for standard definition (AKA “601”), but for high-def (AKA “709”):

y = 0.213 * r + 0.715 * g + 0.072 * b

Which, even if you’re not so into the maths, will give different values for the luminance (the overall level and hence look of the picture). This makes it doubly important that you get your cameraman to record some colour bars at the head of each rushes tape and that your editor checks alignment on his scope before he starts adding captions etc. The best of breed digital picture instruments are from Tektronics who Root6 are pleased to represent.

If you find you have a colour space issue (particularly going between standard and high definition formats) then the Belle Nuit Montage test chart is a good starting point. It can highlight all the common transcoding errors – be it the limited 8-bit range of old D1 videotape to some of the sub-sampling issues associated with HDCam. You can download the file at various resolutions from their website and by injecting it at the start of your workflow any inadequacies are quickly revealed and can be corrected.