displays

Video: Will Direct LED Replace Projection?

Posted on by Russell Trafford-Jones

LCD displays have got to the size and sophistication that they can now be installed instead of projectors in cinemas and smaller theatres. This means a choice is now opening up in what equipment to put into high-end home cinemas, shops and more. Whilst there are good reasons to use LCD displays, called ‘Direct LED” in this talk, there are many pros and cons to be navigated.

Michael Heiss joins us in his usual understated style from ISE starting by outlining the key questions to be asking early in any engagement such as the required screen size, resolution, and aspect ratio. Whilst these are basic, there are further questions such as whether there is a brightness requirement, a need for HDR and of course, what the budget is. Answering these questions will help understand if projection is still the better direction to be going.

If you’re building a direct LED screen, the resolution of that screen will be dictated by the pixel pitch of the modules and the number of modules. For a fine pitch, you may just need a 4×4 array of modules. For a wider pitch, perhaps 8×8 to deliver the same HD resolution. This means your choice of screen sizes will be limited as opposed to projection where the resolution is derived from the projector itself and by adjusting its position you can get any screen size you choose, shape of the room permitting. With the cost of the screen being dependent on both the pitch and the number of modules, Michael advises anyone to go to the manufacturer and get them to specify combinations that could work for your project instead of trying to working out for yourself.

Audio is a big issue for larger screens in a film setting as traditionally speakers have been mounted behind the screens in cinemas. The move to LCD screens prevents speakers being behind the screen, but for large settings, people need to hear audio coming from the area of the screen where the characters are talking. Michael explains that the current practice in a cinema near him is to fill in this dead area of audio with sound from the sides bouncing off the screen. This requires a lot of signal processing and specialist knowledge which is not readily accessible and increases the cost of installation.

Direct LED works well for screens outside due to their brightness, for the smaller single-piece screens the simplicity is ideal for retail and it’s very neat. Bringing in the modular design can also work well but there is more complexity in having a frame to align all the modules, you also then need to ensure you have access to the modules when you need to swap them either from the front or the back. This can have an impact on home cinema design, too, as many screens will be flat against a wall.

With price still being in favour of projectors, it’s clear that there’s room in the market for both types of product. As manufacturers such as Samsung continue to experiment and push forward better and cheaper displays, it’s likely the cost element will continue to be eroded opening up Direct LED to many more people.

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Speakers

Michael Heiss Michael Heiss
Principal Consultant
M. Heiss Consulting

Video: Broadcast Fundamentals: High Dynamic Range

Posted on by Russell Trafford-Jones

Update: Unfortunately CVP choose to take down this video within 12 hours of this article going live. But there’s good news if you’re interested in HDR. Firstly, you can find the outline and some of the basics of the talk explained below. Secondly, at The Broadcast Knowledge there are plenty of talks discussing HDR! Here’s hoping CVP bring the video back.

Why is High Dynamic Range is like getting a giraffe on a tube train? HDR continues its ascent. Super Bowl LIV was filmed in HDR this year, Sky in the UK has launched HDR and many of the big streaming services support it including Disney+, Prime and Netflix. So as it slowly takes its place, we look at what it is and how it’s achieved in the camera and in production.

Neil Thompson, an Sony Independent Certified Expert, takes a seat in the CVP Common Room to lead us through HDR from the start and explain how giraffes are part of the equation. Dynamic Range makes up two thirds of HDR, so he starts by explaining what it is with an analogy to audio. When you turn up the speakers so they start to distort, that’s the top of your range. The bottom is silence – or rather what you can hear over the quiet hiss that all audio systems have. Similarly in cameras, you can have bright pixels which are a different brightness to the next which represents the top of your range, and the dithering blacks which are the bottom of your range. In video, if you go too bright, all pixels become white even if the subject’s brightness varies which the equivalent of the audio distortion.

With the basic explanation out of the way, Neil moves on to describing the amount or size of dynamic range (DR) which can be done either in stops, contrast ratio or signal to noise ratio. He compares ‘stops’ to a bucket of water with some sludge at the bottom where the range is between the top of sludge and the rim of the bucket. One stop, he explains, is a halving of the range. With the bucket analogy, if you can go half way down the bucket and still hit clear water, you have 1 stop of dynamic range. If you can then go a quarter down with clean water, you have 2 stops. By the time you get to 1/32nd you have 5 stops. If going to 1/64 of the height of the bucket means you end up in the sludge, your system has 5 stops of dynamic range. Reducing the sludge so there’s clear water at 1/64th the height, which in cameras means reducing the noise in the blacks, is one way of increasing the dynamic range of your acquisition.

Update: Unfortunately CVP choose to take down this video within 12 hours of this article going live. But there’s good news if you’re interested in HDR. Firstly, you can find the outline and some of the basics of the talk explained below. Secondly, at The Broadcast Knowledge there are plenty of talks discussing HDR! Here’s hoping CVP bring the video back.

If you would like to know how lenses fit into the equation of gathering light, check out this talk from Cannon’s Larry Thorpe.

Neil looks next at the range of light that we see in real life from sunlight to looking at the stars at night. Our eye has 14 stops of range, though with our iris, we can see the equivalent of 24 stops. Similarly, cameras use an iris to regulate the light incoming which helps move the restricted dynamic range of the camera into the right range of brightness for our shot.

Of course, once you have gathered the light, you need to display it again. Displays’ ability to produce light is measured in ‘nits’, which is the amount of light per metre squared. Knowing how many nits a displays helps you understand the brightness it can show with 1000 nits, currently, being a typical HDR display. Of course, dynamic range is as much about the blacks as the brightness. OLED screens are fantastic at having low blacks, though their brightness can be quite low. LEDs, conversely, Neil explains, can go very bright but the blacks do suffer. You have to also take into account the location of a display device to understand what range it needs. In a dim gallery you can spend longer caring about the blacks, but many places are so bright, the top end is much more important than the blacks.

With the acquisition side explained, Neil moves on to transmission of HDR and it’s like getting a giraffe on a tube train. Neil relates the already familiar ‘log profiles’. There are two HDR curves, known as transfer functions, PQ from Dolby and HLG (Hybrig Log Gamma). Neil looks at which profiles are best for each part of the production workflow and then explains how PQ differs from HLG in terms of expressing brightness levels. In HLG, the brightest part of the signal tells the display device to output as brightly as it can. A PQ signal, however, reserves the brightest signal for 10,000 nits – far higher than displays available today. This means that we need to do some work to deal with the situation where your display isn’t as bright as the one used to master the signal. Neil discusses how we do that with metadata.

Finishing off the talk, Neil takes questions from the audience, but also walks through a long list of questions he brought along including discussing ‘how bright is too bright?’, what to look for in an engineering monitor, lighting for HDR and costs.

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Speakers

Neil Thompson Neil Thompson
Freelance Engineer & Trainer

Video: 2019 Display Trends and Hot Display Apps

Posted on by Russell Trafford-Jones

Display technology has always been deeply intertwined with broadcasting. After all, when John Logie Baird first demonstrated his working television, he had to invent both the camera and the display device, then known as at the televisor. He himself worked tirelessly on improving television and less than 20 years after his black and white debut was working on a colour television which used two CRT (Cathode Ray Tubes) to produce its picture culminating in the world’s first demonstration of a colour TV in 1944 – incidentally discovering, demonstrating and patenting 3D TV on the way!

So it is today that the displays define what we can show to viewers. Is there any point in mastering a video to show at 10,000 NITs if there is no display that can show something so bright? Pushing all of Europe and the US’s television programmes to 8K resolution is of limited benefit when 8K TVs are in limited supply and in few homes.

This talk looks at the state of the art of display technology seeing where it’s being used and how. Digital Signage is covered and of course this is where the high brightness technology is developed, for signs outside, some of which could influence more conventional TVs on which we want to watch HDR (High Dynamic Range) video.

When OLED technology first came along it was quickly slated as a great option TVs and yet all these years later we see that its adoption in large panels is low. This shows the difficulty, sometimes, in dealing with the technical challenges of great technologies. We now see OLEDs in wearable devices and smaller screens. The number of the screens is quickly increasing as IoT devices, watches and other electronics start to adopt full screens instead of just flashing LEDs. This increase in manufacturing should lead to renewed investment in this field potentially allowing OLEDs to be incorporated in to full-sized, large TVs.

The talk finished with a look at the TV market covering quantum dots and what people really mean when they mention ‘LED TVs’.

This webinar is from the Society for Information Display and is produced in partnership with SMPTE.

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Speaker

Sri Peruvemba Sri Peruvemba
CEO,
Marketer International