Ever since the release of the XDCAM EX cameras users have been having problems getting good lookin SD pictures out of downconverted HD. Why is this and what can be done about it? This is an issue that effects all high resolution HD cameras and is not unique to the EX’s. There are two key issues.

The first is the way basic software converters handle fields in interlace material and the second is the amount of information inan HD image that must in effect be discarded to get a SD image. At first glance you would think that starting off with lots of picture detail would be a good thing, but in this case it’s not.

Let’s see if I can explain.

Imagine that you have something in you HD picture that over 4 pixels goes from light to dark, in Hd you get a gradual transition from light to dark and all looks good. Now what happens when you take those 4 pixels and convert them to SD. The 4 pixels become just 2 and instead of a stepped change from light to dark the picture now goes instantly from a light pixel to a dark pixel. If these pixels were the edge of a moving object, as it moved the pixels would be switching instantly from on to off and unless the object moved at exactly one pixel per frame you will get a flickering effect. Clearly our nice gradual transition from light to dark has been lost and if there is any motion we may now be seeing flickering edges. Niether of these look good.

So what can be done? Well the best way to improve the SD down conversion is to soften the HD image before it is down converted to prevent this single pixel light to dark switch from happening. You need to end up with an SD image where you go from full light to full dark over at least 3 pixels to prevent flicker (Twitter).

How much you will need to soften you HD by will depend on how sharp it is to start with. Simply turning down the cameras detail settings can be a big help, but even then the best results are often obtained by applying some kind of blur filter in post production. In FCP i find the flicker filter works quite well.

If Indiana Jones were a cameraman his name would be Scott Duncan. An eight time Emmy award winner, Scott is known for his artistry as well as his sense of adventure. Scott has filmed inside war zones, on top of mountains and under raging rivers. Last month he used the new Aaton Penelope camera to shoot one of Manhattan’s most menacing marauders – Donald Trump.

The project was the opening of a brand new season of Celebrity Apprentice with The Donald and a gaggle of…celebrities (who we can’t name right now – you’ll know them when you see them). It proved an excellent opportunity for Scott to become acquainted with Penelope.

The production took place over the course of 5 days and was shot in a studio and at various well-known New York locations. A long time owner of Aaton 16mm equipment, Scott felt comfortable immediately.

“I put her in as many real situations as possible while gathering imagery,” he said. “There are so many great details to the camera, I felt at home almost instantly.”

The Aaton design philosophy has always emphasized hand-held use, and Penelope brings the iconic ‘cat on the shoulder’ analogy to 35mm. Scott’s comments on the subject – “Handheld is very easy, the mag is very soft on the shoulder…that is what those little things on the bottom of the mag are for and they actually really work … I shot a lot of handheld.”

Scott chose to shoot 2-perf, because he is considering Penelope for an upcoming feature, and this was an opportunity to test the format. (The camera can be set to shoot either 2-perf or 3-perf 35mm film). Operationally, he was pleased with changing magazines and control of the camera.

“The Magazines on and off is butter…the operator side buttons for frame rate and other controls is super nice and easy.”

To sum it up, Scott Duncan said, “…amazing this Penelope!” A nice first impression from an adventurous and discerning cameraman.

http://www.blog.abelcine.com

Over the years there have been many, often heated debates over the differences between 8 bit and 10 bit codecs. This is my take on the situation, from the acquisition point of view.

The first thing to consider is that a 10 bit codec requires a 30% higher bitrate to achieve the same compression ratio as the equivalent 8 bit codec. So recording 10 bit needs bigger files for the same quality. The EBU recently evaluated several different 8 bit and 10 bit acquisition codecs and their conclusion was that for acquisition there was little to be gained by using any of the commonly available 10 bit codecs over 8 bit because of the data overheads.

My experience in post production has been that what limits what you can do with your footage, more than anything else is noise. If you have a noisy image and you start to push and pull it, the noise in the image tends to limit what you can get away with. If you take two recordings, one at a nominal 100Mb/s and another at say 50Mb/s you will be able to do more with the 100Mb/s material because there will be less noise. Encoding and compressing material introduces noise, often in the form of mosquito noise as well as general image blockiness. The more highly compressed the image the more noise and the more blockiness. It’s this noise and blockiness that will limit what you can do with your footage in post production, not whether it is 10 bit over 8 bit. If you have a 100Mb 10 bit HD compressed recording and comparable 100Mb 8 bit recording then you will be able to do more with the 8 bit recording because it will be in effect 30% less compressed which will give a reduction in noise.

Now if you have a 100Mb 8bit recording and a 130Mb 10 bit recording things are more evenly matched and possibly the 10 bit recording if it is from a very clean, noise free source will have a very small edge, but in reality all cameras produce some noise and it’s likely to be the camera noise that limits what you can do with the images so the 10 bit codec has little advantage for acquisition, if any.

I often hear people complaining about the codec they are using, siting that they are seeing banding across gradients such a white walls or the sky. Very often this is nothing to do with the codec. Very often it is being caused by the display they are using. Computers seem to be the worst culprits. Often you are taking an 8 bit YUV codec, crudely converting that to 8 bit RGB and then further converting it to 24 bit VGA or DVI which then gets converted back down to 16 bit by the monitor. It’s very often all these conversions between YUV and RGB that cause banding on the monitor and not the fact that you have shot at 8 bit.

There is certainly an advantage to be had by using 10 bit in post production for any renders, grading or effects. Once in the edit suite you can afford to use larger codecs running at higher bit rates. ProRes HQ or DNxHD at 185Mb/s or 220Mb/s are good choices but these often wouldn’t be practical as shooting codecs eating through memory cards at over 2Gb per minute. It should also be remembered that these are “I” frame only codecs so they are not as efficient as long GoP codecs. From my point of view I believe that to get something the equivalent of 8 bit Mpeg 2 at 50Mb/s you would need a 10 bit I frame codec running at over 160Mb/s. How do I work that out? Well if we consider that Mpeg 2 is 2.5x more efficient than I frame only then we get to 125Mb/s (50 x 2.5). Next we add the required 30% overhead for 10 bit (125 x 1.3) which gives 162.5Mb/s. This assumes the minimum long GoP efficiency of x2.5. Very often the long GoP advantage is closer to x3.

So I hope you can see that 8 bit still makes sense for acquisition. In the future as cameras get less noisy, storage gets cheaper and codecs get better the situation will change. Also if you are studio based and can record uncompressed 10 bit then why not? Do though consider how you are going to store your media in the long term and consider the overheads needed to throw large files over networks or even the extra time it takes to copy big files compared to small files.

http://www.xdcam-user.com

I shoot all my own material as Progressive. About the only time I shoot interlace is when shooting airshows where the client specifies interlace, even that looks like it will change to P next year.

Interlace really is a hangover from the past where there simply wasn’t the bandwidth to broadcast full resolution (SD) progressive frames, so the compromise that is interlace was developed to split the frame into 2 half’s, transmitting one after the other. This enabled broadcaster to fit SD pictures into narrower bandwidth than would have been possible for progressive  analogue broadcast. These days with most display technologies centering around progressive scanning I’m not convinced that interlace is the way to shoot. Obviously if your client insists on interlace then that’s what you must deliver.

I supply hundreds of hours of footage to broadcasters, museums and corporate production companies around the world. I have been shooting progressive since 2004. Often I deliver the material recorded as interlace, but containing progressive images. Not once has that caused me a problem. As I write this I am converting some 1920×1080 25P footage to 1920×1080 60i for delivery to NBC. If I had shot 50i that conversion would be very difficult to do and to make look good. Software standards conversion of interlace material is troublesome to say the least. It is so much easier to start of with one frame rate of P and convert to another frame rate P or I. If you start with I then you immediately have a resolution drop if you shoot with a video camera because the fields are created by using overlapping line pairs from the sensor to prevent twitter an aliasing. Converting that already resolution compromised footage to progressive will almost certainly result in a further resolution drop as you will need to do some form of de-interlace procedure. On a big screen that drop in resolution is very noticeable. Converting from P to I on the other hand has none of these issues and frame rate conversions from P to P are easy.

More and more video is ending up on the web or being delivered to computers, so for this progressive is essential. Interlace on computer screens usually looks terrible. In the future it seems likely that television broadcasting as we know it will be replaced with video served over the internet or some other data pipe such as direct to home fiber-optic, again this will almost certainly require progressive material.

More and more broadcasters are now insisting on progressive delivery of HD material, especially for documentary, drama and other high end productions. Often this is because international distribution of progressive is so much easier and the quality better. Sure 25P is not ideal, 50P would be better. But working with progressive material is so much easier than working with interlace.

http://www.xdcam-user.com/?p=239

This looks a great monitor for viewing your 720p work, I hope to get a sample for review, the price is £487 plus postage to the UK…More details as I get them.

http://www.smallhd.com/dp1

8.15am Driving through Glasgow heading for Scottish Television, the day started with a good cloud base, this was handy as we were shooting out of a window overlooking some of the city’s landmarks.

8.50am We are now setting up each to his own discipline, Paul the Director gives John (Cameraman) some last minute ideas about how he wants the inserts to look. John has been a freelance cameraman for a few years now and used to work as a lighting cameraman for Scottish Television before being given the golden handshake by the company. This is a move that has enhanced his career and taken him all over the world. Today he is using his trusted DigiBeta camcorder.

Our shoot today brought many disciplines together, sound (George), lighting spark (Willie), Autocue (Philip), make up artist (did not catch the ladys name) and Lorraine Kelly (Presenter).

10am Lorraine arrives and is taken to make up, we are almost ready to roll, the track, which is a Wally Dolly is set up, HMI lighting is in place and the director Paul discusses some tracking moves with cameraman John.

10.30am Lorraine gets her radio mic “pulled through” which causes some laughter, George uses an “Audio” radio mic but tells me that it will become redundant next year. If you have a UHF Wireless Microphone licence or have had frequencies licensed in channel 69 in the past two years you will already have received a letter from Ofcom regarding the proposed changes for PMSE. The letter informs licensees of Ofcom’s proposal to include channel 69 within the Digital Dividend which will be auctioned for new uses in 2010.  It also details their proposal to replace 69 with channel 38 by the end of 2012. Ch 69 is to be bought over and run by a mobile phone company.

So if you have a radio mic system you could find it is useless at some point late summer 2010.

11am The first piece to camera (PTC) is in the can and we all move to a new position, this goes on for the rest of the day till we film the last PTC is finished.

Lorraine was great to work with she is as friendly and bubbly as you see on GMTV, the programme we were working on goes out in August 2009 on Scottish Television called Scotlands DNA Secrets which is made by SMG Productions, part of STV, DNA Stories sets out to help people find answers to unresolved family issues. If selected, STV will come to film you in the comfort of your own home where the DNA sample will also be taken. When the test is complete, Lorraine will where possible bring family members together, in private, to reveal what could be life-changing results.

Lorraine says: “DNA testing is an intriguing subject and I’m very excited about filming another series of DNA Stories. I have no doubt the second series will be as successful as the first.“