Video: Canon Lenses – A Tale of Three Formats

Lenses are seen by some a black art, by some as a mass of complex physics equations and others who see them as their creative window onto the stories that need to be told. Whilst there is an art behind using lenses, and it’s true making them is complex, understanding how to choose lenses doesn’t require PhD academia.

SMPTE Fellow Larry Thorpe from Canon is here to make the complex accessible as he kicks off talking about lens specifications. He discusses the 2/3-inch image format comparing it with super 35 and full frame. He outlines the specs that are most discussed when purchasing and choosing lenses and shows the balancing act that all lenses are, wanting to maximise sharpness whilst minimising chromatic aberration. On the subject of sharpness, Larry moves on to discussing the way the camera’s ability to sample the video interacts with the lenses ability to capture optical resolution.

Larry considers a normal 1920×1080 HD raster with reference to the physical size of a TV 2/3inch sensor. That works out to be approximately 100 line pairs per millimetre. Packing that into 1mm is tricky if you wish to also maintain quality of the lines. The ability to transfer this resolution is captured by the MTF – the Modulation Transfer Function. This documents the contrast you would see then certain frequencies are viewed through the lens. Larry shows that for a typical lens, this 100 line pairs would have 70% of the original contrast. The higher the frequency, the lower the contrast until it just becomes a flat grey. Larry then looks at a 4K lens showing that it’s needs are 200 line pairs per mm and looking at the MTF, we see that we’re only reaching 50% contrast

Aberrations are important to understand as every lens suffers from them. Larry walks through the 5 classical aberrations, focus and chromatic. To the beginner, chromatic aberrations are, perhaps, the most obvious where colours are seen on the edge of objects, often purple. This is also known as colour fringing. Larry talks about how aperture size can minimise the effect and keeping your image above the 50% contrast limit in the MTF will keep chromatic aberration from being obvious. As a reality check, we then see the limits that have been calculated as limits beyond which it’s simply not possible to improve. Using these graphs we see why 4K lenses offer less opportunity to stop down than HD lenses.

Sharpness zones are zones in lenses optimised for different levels of sharpness. Within the centre, unsurprisingly is the highest sharpness as that’s where most action is. There is then a middle and an outer zone which are progressively less sharp. The reason for this is to recognise that it’s not possible to make the whole image sharp to the same degree. By doing this we are able to create a flatter central zone but with a manage decrease at the corners.

Larry moves on to cover HDR an mentions a recent programme on Fox which was shot in 1080p HDR making the point that HDR is not a ‘4K technology’. He also makes the point that HDR is about the low-lights as well as the specular highlights, so a lens’s ability to be low-noise in the blacks is important an whilst this is not often a problem for SDR, with HDR we are now seeing this coming up more often. For dramas and similar genres, it’s actually very important to be able to shoot whole scenes in low light and Larry shows that the large number of glass elements in lenses is responsible for the low light performance being suboptimal. With up to 50% of light not making it through the lens, this light can be reflected internally and travels around the lens splashing the blacks. Larry explains that coating elements can correct a lot of this and careful choice of the internal surface of the lens mechanisms is also important in minimising such reflections.

Telephoto lenses are lenses which have variable zoom. Larry shows how Canon developed a lens so fully frame a 6 foot athlete from 400 metres away so that they were fully framed on a 2/3″ sensor, but still with a wide angle lens of 60 degrees. With such a long zoom, internal stabilisation is imperative which is done by a very quick active feedback sensor.

So far, Larry has talked about the TV’s standardised 2/3″ image sensor. He now moves on to cover motion format sizes. He shows that for Super 35, you only need 78 line pairs per millimetre which has the knock-on effect of allowing sharper pictures. Next Larry talks about the different versions of ‘full frame’ formats emphasising the creative benefits of larger formats. One is giving a larger field of view which Larry both demonstrates and explains, another is greater sharpness and by having a camera which can choose how much of the sensor you actually use, you can put all sorts of different lenses on. Depth of field is a well known benefit of larger frame formats. The depth of field is much lower which, creatively, is often much desired, though it should be noted that for entertainment shows in TV, that’s much less desirable whilst in films, this is an intrinsic part of the ‘grammar.

As the talk comes to a conclusion, Larry discusses debayering whereby a single sensor has to record red, green and blue. He explains the process and the disadvantages versus separate sensors in larger cameras. As part of this conversion, he shows how oversampling can improve sharpness and avoid aliasing. the talk finishes with an overview of solid storage options

Watch now!
Speakers

Larry Thorpe Larry Thorpe
National Marketing Executive,
Canon USA Inc.

Video: How to succeed in OTT in 2020

With the streaming market maturing, keeping ahead of competitors requires a layered strategy, particularly for entrants to the market who don’t have Amazon levels of funding. There are success stories out there, so what are the ingredients for success? This recored webinar looks at these questions an shares advice on succeeding in today’s market.

Rahul Patel from Ampere Analysis is first giving an overview of the OTT/streaming market. Within the UK and the US, we now see, he explains, 35% of subscriptions belonging to those 45 and older thus the market is maturing and increasingly offering a wider choice of genres to a wider selection of people. In general, services stand out through their content which is often done through original productions with Netflix now investing almost the same in original programming as the BBC does across all its channels. Rahul shows statistics showing that the percentage of non-US productions is increasing with Netflix and Amazon prime both trying to create programming which is more appealing to their non-US viewers.

An alternative to original programming is to focus your offering. For example, services such as AcornTV focus on UK crime drama, Crunchyroll is focussed on Japanese-made programming and Mubi is 100% films. Though in one market, a very narrow niche may not provide the customers needed to make the service viable, but expanded across all markets, that can all change. Another way services are attracting subscribers, Rahul details, is through bundling either with multiple services being discounted when purchased together, free subscription with hardware purchase or partnerships between big players such as network operators.

As the stacking of services continues to increase, Rahul foresees a future role for aggregators and simplifying the subscription to one payment. Aggregation would involve a single search interface unifying disparate services and could be provided by giants such as Apple and Amazon.

US Industry Avg SCOD Uplifts. Source Reemah Sakaan, BritBox

Next up is Reemah Sakaan from BritBox, which launched in the US in 2017, now in the UK as of 2019 and soon Australia. She explains their journey to market discussing how it can take long time to get rights and forge a true identity, but once that is done, an easy to understand offering can be quickly taken up by viewers. Reemah notes that Covid-19 has pushed a hugh change in viewership both in terms of viewing hours but also subscribers and underlined the importance of their embedded live feed which allows them to go live with special events such as the Royal Wedding along side the traditional VoD offering. This helps them be a unique service and maintain differentiation from competitors.

The last of the presentations is from Simon James from Applicaster. Applicaster’s focus is on providing apps for streaming services. Major issues are in scaling your app on all platforms and trying to manage testing across different OS types and versions. Simon says that the effort needed to keep up with all of this can sap energy and innovation from the team. It also makes it hard to be agile and respond to the market and viewers within the pandemic being a fantastic example of why.

The video ends with a Q&A covering increasing subscriber churn which may lead to annual discounts rather than a monthly subscription. Reemah explains that the first 100 days is key in keeping subscribers. Other questions cover the need for consistent user experience across platforms, approach to expansion and the applicability of your content to your viewers.

Watch now!
Speakers

td>

Reemah Sakaan
Group Director, SVOD at ITV
Chief Brand and Creative Development Officer, BritBox Global
Rahul Patel

Rahul Patel
Analyst,
Ampere Analysis
Simon James

Simon James
Head of Sales Engineering,
Applicaster

Video: The future of addressable TV advertising in the UK

When it comes to advertising, there’s a lot of value in understanding who you’re talking to. This video examines the practicality of that within the UK and the relative value that brings. Nigel Walley from Decipher looks at how the landscape is changing both in the ability to address the TV externally and the information available within the home.

Nigel starts by looking at how the broadcast TV companies and the online streaming companies are able to target and concludes that broadcast can often fine tune to the region and and include dayparting whereas though we assume streaming companies can target by individuals, in reality Nigel asserts, they typically target by household. He goes further to explain that almost 50% of viewing is still linear TV with YouTube taking up 12.4% of the 50% which remains of the 4hours and 42 minutes of average viewing time per day.

Nigel makes the point that with HbbTV and many of the streaming services being available on the ‘big screen’, it makes the idea of ‘broadcast’ vs ‘streaming’ a nonsense as they are already converged. The big difference is in how we can provide the ads to these platforms. The Virgin and Sky closed platforms comprise nearly 13 million viewers with Freeview plus others making up nearly 16 million. Nigel highlights that 30% of viewing is with the BBC and hence no advertising, although trailers may be delivered using addressable technologies.

Nigel explains that Sky’s Adsmart has been extended to Virgin cable. Then explains how YouView and other channels move up to the big screen – the TV. The important issue for publishers is how the Sky and Virgin platforms end up as controlling influences. Nigel explains the Linear Addressability of the platforms showing that YouView is the next potential area this will happen. There’s also the opportunity for smart TVs themselves to help in delivering these ads. “What can a broadcaster do alone” asks Nigel which he answers by saying ‘very little’ unless they are Sky or Virgin in the UK. They can deliver addressable TV into apps and computers, however.

Nigel finishes with a call to action to the broadcasters to change their focus from individual apps to the ways they and agencies can work together to reach more, and more targeted viewers.

Watch now!
Speaker

Nigel Walley Nigel Walley
Managing Director,
Decipher

Video: How to Successfully Commission a SMPTE ST 2059/PTP System

PTP is the beating heart behind video- and audio-over-IP installations. As critical as black and burst reference, it pays to get it right. But PTP is a system, not a monolithic signal distributed around the facility. Unlike genlock, it’s a two-way conversation over networked infrastructure and whilst that brings great benefits, it changes how we deal with it. The system should be monitored, both at the ST 2059 layer and network layer. But before we even get to that point, implementation requires care particularly as the industry is still in the early phases of developing tools and best practices for project deployments.

Leigh Whitcomb from Imagine Communications has stepped up to bring us his experiences and best practices as part of the Broadcast Engineering and IT Conference at NAB. This talk assumes an existing level of knowledge of PTP. If you would like to start at the beginning, then please look at this talk from Meinberg and this from Tektronix.

Leigh starts by explaining that, typically, the best architecture is to have a red and a blue network. A grand master would then be on both networks and both would be set to lock to GPS. He explains how do deal with prioritisation and preventing other devices from becoming grand masters. He also explains some of the basic PTP parameter values such as setting the Announcement time outs. Other good design practices he discusses are where to use Boundary Clocks, avoiding PTP Domain numbers of 0 and 127 plus using QoS and DSCP.

As part of the commissioning piece, Leigh goes through some frequently-seen problems such as locking up slowly due to an incorrect Delay Request setting or the Grand Master announce rate being the same as the timeout. To understand when your system isn’t working properly, Leigh makes the point that it’s vital to understand in detail how you expect the system to behave. Use checklists to ensure all parameters and configuration have been applied correctly but also to verify the PTP packets themselves leaving the GM. Leigh then highlights checklists for other parts of the network such as the switches and Media Nodes.

There are a number of tools available for faultfinding and checking compliance. As part of commissioning, the first port of call is the device’s GUI and API which will obviously give most of the parameters needed but often will go further and help with fault finding. WireShark can help verifying the fields in the packets, the timing and message rates. Whilst Meinberg’s Track Hound is a free program which allows you to verify the PTP protocol and Grand Masters. The EBU List project also covers PTP/ST 2059. Helpfully, Leigh talks through how to use Wireshark to verify fields and message rates.

In terms of Testing, Leigh suggests running a packet capture (PCap) for 48 hours after commissioning to verify any issues. He then highlights the need for redundancy testing. This is where understanding how you intend the network to work is important as redundancy testing should also be combined with network testing where you deliberately pull down part of your network and see the GMs change as intended. This changeover will be managed by the Best Master Clock Algorithm (BMCA). When troubleshooting, you should use your monitoring system to help you visualise what’s happening. A good system should enable you to see the devices on the network and their status. Many companies would want to test how successfully the system recovers from a full failure as this will represent the maximum traffic load on the PTP system.

How to watch
1) Click on ‘Add to favourites’
2) Register for free – or log in if you are already part of NAB Express

3) You will then see the video on the left of the screen.

Watch now!
Speakers

Leigh Whitcomb Leigh Whitcomb
Architect,
Imagine Communications