Sunday, October 06, 2019

Experiments with white light (it's complicated!)

I've often run a day's training course for broadcast engineers who want to get up to speed with calibrating monitors and projectors; typically to rec.709 but increasingly to P3 as HDR and 4K/UHD are becoming a thing.  One of the principles I've always struggled to get over is Metamerism; that inability to see/measure colours correctly if your measurement device (camera, eye) is tristimulus and your source of illumination does not have a daylight-like spectrum (so LED lights, typically).

A few month's ago I got one of Chris Wesley's excellent home-brew spectroradiometer kits; from now on referred to as the ghetto-spectro.  Read Chris's excellent documentation about how you can make really quite accurate spectrum measurements with modest parts so long as you can accurately calibrate the thing - and this is where the spectrum of Mercury comes in useful. Mercury has two peaks in the visible spectrum at 546nm and 436nm and you can guarantee that a compact fluorescent bulb will have a decent amount of mercy in it.

the ghetto-spectro pointed at the mercury containing CFL bulb on my workshop bench

the measured output showing the various peaks of different elements

the image from the diffraction grating in the iPhos

So, watch Chris's video which tells you how to calibrate to the two Hg-peaks, and pay special attention between 540 and 550nm as Terbium lurks very closely to the 546nm peak (green) of Mercury.
Terbium is at 543nm, very close to Mercury at 546nm

OK, now I have a calibrated spectro I can turn my attention to experiments with white light and perception. I build a box with two isolated sections, painted inside with a very reflective white primer paint. In the left-hand cavity is one of those RGB-mixer bulbs based on LED technology (and controllable from an app; very 2019!) and in the right-hand section is a broad-spectrum white light. 




Thus equipped I can now mix the RGB values in the left-hand side to produce a white light that matches the right-hand side from my perception. As you can see; the camera in my iPhone does not agree! BUT, I promise you, to my eyes the two white are a really good match. I have spent may years "racking" studio cameras (matching their colourimetry for live TV shows so that the lighting director doesn't shout at you!) and eye-matching displays (typically a good domestic TV to a grade-1 broadcast monitor) - I have a better eye for colour than most.

So, at this point I should show the spectro output for the two light sources;


the right-hand broadband white light; reasonably continuous spectrum



the RGB-mixer bulb; three clear peaks


So; I took photos using three different cameras; an iPhone 8 using the native Apple photo app, a low-end Android tablet using the Google photo app and a 2015-vintage Fuji Finepix 5600 bridge camera. All three rendered the RGB-white differently (remember , that to my eyes it's the same white as the broadband white bulb) and they also minimized the differences in the colours of the juggling thuds I used as colour references in the two box sections.

From the iPhone 8




from the Android tablet




from the Fuji Finepix





Finally I should make a note of how my perception of the colours varied;

I need to think about this a bit more to relate the spectra of the two bulbs to the likely sensitivities of the cameras; but, it does show that observer metameristic failure is a things!

Monday, September 23, 2019

What I saw at IBC2019

Eizo CG3145 “mk.2?” – Revision of the current model “Prominence” monitor - see my post from last year.

It’s exactly the same dual Panasonic IPS (LCD) display module and modulated LED backlight as the current version (and indeed the Sony X310 replacement for the X300) with the following upgrades;
  1. Quad 3G and single-link 12G inputs for current gen 4K/UHD/HDR standards. If you need to go to 18G standards (so 4K, 12 bit, RGB and 60P) it still supports HDMI 2.0 and DP. Once nicety is that it has SDi out and can convert signal standard as an active loop-through (but not converting colour space, sampling structure etc – obviously),
  2. Internal probe; a higher quality photometer than the 319X but I’ll have to test it against a “proper” probe before we make comment; they assured me ColourNavigator’s “sensor correlation” function would work as other CG-series displays. See my video.
  3. Three user-defined cages and BITC as per Sony’s 4k monitors – this has been mentioned by several facilities as reasons why they won’t leave Sony – aside from the BITC feature having been broken in the Sony displays since v.2 firmware I don’t believe grading room displays need either of these, but it’s good to have an answer (I’d say exactly the same as point 1. Above)
  4. Much nicer control via a big knob on the front.
  5. Price – will be the same as the current CG3145
  6. Availability – they reckon there will be pre-production demo examples in January and supply at start Q2.
They made some point about having improved the FPGA code in the panel for better sharpness – sounded like marketing waffle; and in truth savvy customers don’t want a monitor “sharpening up” their pictures; pixel-to-pixel is what’s needed; brutal honesty rather than the picture processing you get on a domestic TV.


Emerald KVM system from Black Box; it comes in three product skews;
https://www.blackbox.com/en-us/products/black-box-brand-products/kvm/control-room-kvm/4k-kvm-over-ip-switch
  • The basic – tops out at 2 x single-link displays (1920x1200) 
  • The “professional” – same performance but has tighter integration with their manager
  • The 4K – supports a single 4096-pixel wide display.
Points to consider;
  1. Price – the basic and professional are very akin to Amulet pricing (bear in mind Amulet Tera2 products do 4 x single link or 2 x 4K displays) – so typically £1,000 per end-point (sender and receiver); Amulet external T2 would be £1,400 (sender) + £700 (receiver). The 4K product which is what now competes with DX-H4T/DZ4 from Amulet is around twice the price (about £3,900 for sender/receiver pair). Add onto this the cost of a broker (their own 1u Linux box) AND they heavily push you to Black Box managed switches (essential if you’re using all the broker features),
  2. Encryption – AES256 with key-exchange is the clear via the broker’s database; we couldn’t sell this to anyone who is looking at a TPN audit,
  3. Bandwidth – max’es out a gigabit Ethernet (in fact you need the second NIC if you want to use two screens); remember, Amulet plays nicely with internet-type bandwidths
  4. Switch requirements – As mentioned, BlackBox manages switches preferred, but whatever you use jumbo frames and IGMP-snooping is required. Amulet plays nicely with all layer-2 ethernet switches.
Niceties;
  • Broker is better to use than Tera connection manager
  • ZC supports both PCoIP and RDP (their protocol is Windows RDP!)
  • As you’d expect from a modern KVM it is reasonably transparent, but full-screen HD video playback was (I thought) worse than Amulet (and remember Amulet tops out at 200Mbit/sec rather than the 2 x GigE that the Emerald needs)
So in fairness I don’t think there is any scenario (other than owning existing plant) where we could sell it as a better option than Amulet (or a Teradici option).


Streambox’s DolbyVision remote workflow
http://www.streambox.com/post-production

StreamBox have implemented eCMU functionality in their Chroma range which means they can take the DolbyVision metadata across the IP-SDi feed and decode the rec.709 fold-down data at the far end and display dual-6G outputs on and HDR monitor and a rec.709 display (typ. a decent TV). The powerful thing is that by having the Dolby tone-mapping algorithm with all the lift/gamma/gain tweaks in the HDR stream they can produce a pixel & colour accurate SDR version at the far end with no extra bandwidth required. Super-cool.


Canon DP-V3120 4k/UHD/HDR grading monitor
https://www.canon-europe.com/video-cameras/dp-v3120

We sold a few of the earlier gen Canon DP-V3010 4k displays and although they were good 4k displays their HDR abilities were more limited than the X300 – in fact today they would be an equivalent to a £3.5k Eizo CG319X.
The new monitor uses the same Panasonic panel & backlight as the Eizo and Sony, but in this case it is a single-layer IPS which means the blacks are probably not as good as the CG3145 and the X310. I’d have to test that when we can our hands on one.
  • 2,000Cdm-2 max light output – probably because it’s only a single layer, they’re letting all the light through. Not sure why this is a benefit as nobody (Netflix, Fox, Warners) are specifying 2,000Cdm-2 deliverables and the next bump to DolbyVision will be to 4,000Cdm-2 so this seems to be neither fish nor fowl – much like the Flanders 3,000Cdm-2 monitor.
  • Tone-mapped false colour display – this is very nice; As far as I could tell this is nerly as good as Leader’s “CineZone” display but available in the monitor.
  • Same set of inputs as the new Eizo
  • Sub £20k price tag

ColourSpaceCMS colour management and LUT building software.
https://www.lightillusion.com/colourspace.html

We sometimes sell a LightSpace license with Klein colour probes and I tend to then provide a day’s training (doing it next week at a customer's).
  • Much more modern interface – lots of people complain that LightSpace looks a bit 1990s and things like loading LUTs and talking to patch generators takes a few mouse clicks rather than being auto-detected. ColourSpace seems to address all of this. I've never found this to be an issue; if you've spent thousands on a probe and software you should really get familiar with it.
  • Profiling engine can run whilst you are manipulating LUTs – very cool; will go some way to addressing the two hours of thumb-twiddling I have to do whilst profiling a display.
  • Multiple probe support – you can be profiling two displays at a time; but with probes costing >£6k I wonder who will use this?! Monitor manufacturers at their factory, probably.
  • Price – near-free upgrade from LightSpace depending on age of license.
We never really offer LightSpace as a product by itself; always as part of a package and as part of the colourimetry training day.


Leader LV5900 – 8K test and measurement
https://www.leader.co.jp/en/event/7318
  • 8K (so quad 12G) version of the LV5600/LV7600 series we sell.
  • Price – silly money! >£50k basic

AJA Image Analyser – HD/UHD/4K/HDR test and measurement
https://www.aja.com/products/hdr-image-analyzer

They’ve been selling this for a year as a competitor to the Leader but I don’t know it’s HDR abilities.
  • Quad-12G – now can operate as a 4 x 4K machine; perhaps an OB that is sourcing Slog3 cameras and delivering both HLG and rec.709 would find this udeful?
  • Price - £16k (so cheaper than an HDR/4K optioned Leader)
Also – all the Hi5-4K+ and associated boxes now support Dolby metadata passthrough so no more hooking up the USB control to force displays to switch between rec.709/PQ/HLG. Nice.



The Bryant Unlimited cable manufacturer's meal - the highlight of my professional year!





Saturday, August 03, 2019

Calibrating the Calibrator - Colour management with Eizo CG319X

I've spent a lot of time demo'ing these monitors recently and the thing that tickles customers the most is correlating the internal sensor to an external probe.

https://youtu.be/LB6HFOBJU2c

 

Saturday, April 20, 2019

Electronics, disasterous career choices and good techy YouTubers...

The last few months have been a bit of an education for me; I changed jobs twice and kinda wished I hadn't - neither has been ideal. However, I wound up with six weeks with not much to do (I did a few days of freelance colour work) but I took the opportunity to finish off my home fixing bench;


After this I resorted to my usual cathartic activity of building a hand-held games console based around a RasPi and fitted into the dead carcass of an old Gameboy/Gamegear etc. I didn't make any videos of this project (unlike the Gamegear from last year https://youtu.be/Mt1VP-AjSQU);



BUT, back to the most recent build; I was really pleased how it worked out, probably the most tidy one I've done to date. I also implemented a proper shut-down script so the power button doesn't just crash the Pi (and I monitor the LiPo's voltage to avoid the system crashing that way too).




The other thing I took to whilst off was to start learning the Python programming language - if you're looking to get back up to speed with coding Python seems to cover a lot of the principles of modern scripting languages - the thing that has blown me away the most so far is the list data type - a list can have different data types within it! Perhaps all modern languages have this, but my degree in Maths and Programming in the mid-eighties did not prepare me for such things!
Can I recommend Jamie Chan's book "Learn Python in one day and learn it well" - as someone who still has a bit of C and VB experience it has bee good for me.

I have also been catching up on my favourite electronics YouTubers;

https://www.youtube.com/user/rossmanngroup
Louis Rossman - Apple repair guy and the best example of surface-mount rework and diagnostics you'll see.

https://www.youtube.com/user/bigclivedotcom
Big Clive - more focussed on big volts and tearing down badly made power electronics!

https://www.youtube.com/user/greatscottlab
Great Scott! My kind of small project builds with something of a focus on Arduino

https://www.youtube.com/user/FFcossag
A brother broadcast engineer who fixes stuff

https://www.youtube.com/channel/UCDbWmfrwmzn1ZsGgrYRUxoA
The Post Apocalyptic Inventor - motors and generators are the emphasis of his builds

https://www.youtube.com/user/EEVblog
Dave Jones of the eevBlog is a design engineer who seems to know everything about electronics; really engaging style too.

So, not sure how 2019 is going to play out - one thing I have realised is that my plans of giving up all this broadcast engineering nonsense are perhaps closer than I thought; maybe the teaching PGCE is even closer than I thought...

Saturday, January 12, 2019

Is there an HDR mastering display that costs less than £20k? Not yet.

I was asked to take a look at the ASUS PA32U monitor - a 32" display that (when I first saw it last year) was initially an sRGB, Adobe RGB, HDR10 high-end graphics/gaming monitor. It comes in at sub £2k and so is expensive for home or office use but almost free from a film/TV perspective. Most interetsingly it could hit >1,000Cdm-2 peak white and unlike OLED displays (typ. Sony BVM-X300) it doesn't suffer ABL as more than a small percentage of the display hits peak white.

I gave the manufacturer a few pointers - essentially if it is going to have any application in film and TV it should at least support HLG and DolbyPQ. So, just before christmas a new itteration of the monitor arrived and here is a little video.

A few things to note;

  1. Terrible "blooming" near black; if it was a CRT it would be akin to bad internal reflection within the tube.
  2. The blue primary is not as good as it should be - it can't even hit 100% of rec.709
  3. Ironically, however, it does manage 84% of rec.2020 - just shows you can't get too hung up on very saturated colours,
  4. There is some sort of noise-coring going on; you should be able to disable that in the menues.
LightSpace reports; http://www.engineersbench.com/phil/docs/ASUS_PA32U/
https://youtu.be/hYCJh9ujhxw