The Art of Shooting Progressive
I get so many e-mails from cameramen complaining about the poor results they get when shooting in progressive scan mode with their camcorders, that I thought it was about time I wrote a tutorial on the subject. The usual complaints are about flickering or strobe-like footage, or images that look blurred and un-sharp when compared to interlaced shot footage.
First, let me give you a little bit of background information as well as a few other snippets that might surprise you.
Interlace is a technique for transmitting signals to our television sets that has been around since 1936. For the record, the progressive scan system has also been around for the same amount of time in the form of John Logie Baird’s 240-line mechanical progressive scan system. At the time there wasn’t enough bandwidth to broadcast and transmit progressively, so the interlaced system had to be used. In a nutshell, an interlaced frame is basically a progressive frame that has been sliced up into lots of lines, and each set of alternating lines are transmitted at different times, but so fast it gives the illusion of one frame. Interlaced technology was designed for CRT (cathode ray tube) televisions, not LCD HD TVs or LCD computer displays. Interlacing causes problems on modern LCD TVs and computer displays. Although a lot of modern programmes are shot progressively, there is an even balance of progressive and interlaced footage being shot these days.
Interlaced footage introduces all kinds of issues including ‘ line twitter’ and ‘interlace tearing’. These picture defects show up in certain circumstances more than others, for instance, somebody on TV wearing a shirt with fine dark and light stripes, on TV these stripes would appear to be ‘twittering’.
Basically, interlaced technology is a very old and dated way of transmitting signals to our television sets, and it will soon be dead. These days, most of us own modern LCD HD television sets (all of which are progressive by their very nature), and most modern programming is shot on progressive scan HD camcorders. Progressive scan HD footage and progressive scan broadcasting is the future. If you want to ‘future-proof’ (whatever that means) your footage, it must be shot in HD and in progressive mode. However, the future will be 1080p progressive scan at higher frame-rates such as 48p and 50 and 60p. Footage cannot be truly future-proofed. You could shoot 720p at 50 or 60fps, and it will be good. But 1080p at 25p would not be good future-proofing. Whether to use 24, 25, or 50 and 60p or 50 and 60i is currently an artistic decision.
This short tutorial is to re-educate those who are used to shooting on interlace formats. Those who are used to brandishing a Sony PD170 around like they are on their last line of cocaine are going to have to seriously re-think their shooting techniques. Flitting a progressive scan camcorder around handheld with aggressive and jerky movements simply won’t cut it.
You’re probably aware that most Hollywood movies that you see at the cinema as shot in either 24p or 25p as in 25 frames of film per second. So you’re probably wondering why all those movies look great at the cinema and don’t have the so-called ‘judder’ or ‘flicker/strobe’ effects that your progressive scan camcorder appears to be riddled with. The simple answer is because Hollywood production companies hire in a professional DoP (Director of Photography) and pay him/her a colossal amount of money to get it right. The DoP knows exactly how to ‘Block and Stage’ every shot in such a way that prevents any judder or flicker in the final footage.
You have to shoot more like a professional DoP, as opposed to a testosterone-driven teenager on a mission. This means smooth, slow, and very steady shots.
Having said that, things do not have to be steady. Witness Bourne Identity, Saving Private Ryan, Band of Brothers for example, and many other shots in big movies. Munich, Minority Report and 24 are other major examples, Spooks is yet another. The fact of the matter is that once the eye starts watching progressive footage it will fill in the blanks; this is persistence of vision. The problem of judder usually happens with medium speed objects. Slow movement and faster movement don’t suffer. If you go with the usual idea of an object taking five seconds to cross the screen during a pan for example, you will see judder. This may be why some TV guys had trouble with it.
I think one of the problems may be that people who are shooting in progressive scan mode aren’t doing enough ‘camera movement’. They may be locking the camera off on the tripod and letting objects pass through as opposed to actually moving the camera into and around the scene.
A few years ago somebody asked me what was the best camcorder shooting techniques course they could go on, I told him that he should get in touch with the NFTS (National Film & Television School) in Beaconsfield and do one of their Super16mm film camera short courses. He told me that he shoots on a digital tape formats and that he had no interest in film and couldn’t understand why I would recommend such a thing. I explained to him that if you have to pay for film stock and then pay for the developing and processing of it, you tend to think long and hard before pressing that record button. Just this one factor alone will improve the quality of your footage no end. Of course the other thing about learning to use a film camera is that you are disciplined in the art of incredibly steady and smooth shots, you have to, because at 24 or 25 frames-per-second your footage would suffer from judder and flicker; that’s right, it happens in the film world too.
So here goes. When shooting in progressive mode with your camcorder it’s important to ‘follow the action’. Here’s an example. If you were to ‘lock’ your camcorder off on a tripod and set the zoom to medium/wide in a street scene and film a car as it drove past, in progressive mode the car would enter the frame from the right (depending on which way the car was heading), then ‘judder’ or ‘flicker’ its way across the frame, and finally leave the frame from the left. There’s a better way to shoot this car in progressive mode. Instead of locking the camera off on a tripod, you would carry out a panning shot instead; panning the car as it drives past. This way the car won’t ‘judder’ its way through the frame because you are ‘following the motion’ of the car. But, the shops and buildings behind the car would now be moving across the frame, and they would start to ‘judder’ across the frame instead. So to alleviate this problem of background-building-judder, you would adjust the camcorder’s aperture by opening it up to make the depth-of-field shallower hence knocking the background out of focus slightly. Making the shops and buildings slightly out of focus will hide the fact that they are ‘juddering’ across the frame and the end result will be beautifully crafted footage that is crisp, sharp and luscious with that superb progressive look. However, at the distance you would need to be to follow the camera with a pan, the background will most probably be moving too fast to have any noticeable judder. Furthermore, the human eye will ignore the judder because it will be focusing on the object of interest; in this case, the car. And that is one of the main reasons why programmes like 24 and Spooks can do lots of handheld work without any issues. They compose the shot and follow the object of interest. Wide shots are steady; people do not walk across the frame, but into and out of it. Speaking of which, Steadicam shots should be a judder nightmare when shooting in progressive mode, but they aren’t because they use parallax. Movies will use jibs and dollies which use parallax. They NEVER EVER pan, and they rarely ever tilt. BBC documentaries do panning and tilting, but only very slowly or very quickly; nothing in between.
Of course, the above is just one small example of how to eliminate the so-called progressive ‘judder’ look; there is a whole school on the subject.
Basically, if you think ‘Hollywood’ you won’t go far wrong. By this I mean ‘follow the action’ and ‘move into a scene’ with tracks, dollies, Steadicams, jibs and other grip equipment, don’t just zoom in. Work out each individual shot carefully before carrying it out. Think about how you can avoid pans, zooms and erratic hand-held shots, all of which are ‘judder’ magnets. It is possible to hand-hold your camcorder in progressive mode, just don’t ‘flit’ the camcorder around like a lunatic. Be steady, smooth, stable and follow the action. Pans can be done slowly or quickly (nothing in-between), same for tilts. Handheld can be done, I do it all the time, and purposefully move it around erratically sometimes with no issues. Follow the action, manage the movement. With handheld you need to keep it smoother on the wides than you do at the telephoto end.
How about this, remember doing the ‘egg and spoon’ race at school? Well gaffer-tape two desert spoons to the underside of your camcorder with one spoon sticking out either side. Then place your camcorder down on a table (or other flat surface) and take two eggs out of the fridge and place them on the two spoons. Now hit the record button, pick your camcorder up and go for a walk around your house, up and down the stairs and then around the garden. Film a 2 or 3 minute shot both with and without the eggs, and then compare the footage. Be sure to do the first take with no eggs, and then do the second take with the eggs. You’ll be surprised at the results. Then in future, just pretend that your camcorder not only has two eggs balanced on spoons, but also pretend that there is a reel of 32mm film bolted on the back and you are paying for the film stock and developing and printing, and the whole process of this is costing you around £65 per minute. This combination of thoughts will leave all your progressively shot footage totally judder and flicker free and above all, professional.
When shooting in progressive mode don’t forget to turn the shutter on and set it to 1/50th. This is the equivalent of a ‘double gate’ effect of a projector i.e. sharpening up the look of the footage. With no shutter the footage will have a slight ‘blur’ about it.
Shooting in progressive mode will also give you more of a ‘film look’, which is ideal for creative productions such as music videos and films, either short or feature. Overall shooting in progressive has a more ‘expressive’ look about it. A woman walking along the beach with a long flowing dress will make her movements (arms, flowing dress etc) look much more expressive, this will totally transform and bring the scene to life distinguishing it from that horrible ‘news look’ of interlaced footage. However, this also depends on the project. I find that pop concerts for example look weird in progressive scan 25p but look outsounding in 1080i and 720/50p
Shooting progressively is all about re-educating yourself, you have to go back to school and learn to shoot all over again.
As a progressively shot frame is one complete/whole frame (just like a picture taken on a digital stills SLR camera) it is easy to take a frame grab off the timeline and import it into a photo manipulation programme like Photoshop, Lightroom or Aperture for example, and re-scale it to 300dpi (from it’s default 72dpi) and print it out or publish it as a still photo on the web. Because the still is free of interlacing lines it will be crisp and clear with zero interlace ‘tearing’. You could see a progressive scan camcorder as a digital stills SLR camera taking 25 photographs per second; only lower resolution of course. Years ago I was a stills photographer and I owned many stills film cameras, one of which was a Nikon F3. At the time you could buy a high-speed motor-drive for this camera that was capable of shooting 13.5 fps (frames-per-second), there were other high-speed stills cameras that could do 25 fps, which is the same as film. Of course you had to attach a ‘bulk film’ back onto your camera and buy your film stock on rolls as opposed to a 24 or 36 exposure cartridge.
The advantages of shooting progressive are endless. For example, if you are a low-budget independent filmmaker it’s much easier to do a digital transfer to film if the footage was shot progressively to start with. Shooting progressive is also a good way to ‘future-proof’ your footage; there is no place for interlace in the future. As I’ve already mentioned, taking still frames off the timeline and using them as still pictures is easy.
Other advantages are that progressive scan compresses much more efficiently for DVD etc. You can pan, zoom, and crop progressive scan footage far more easily than interlace. For example if you have progressive footage and want to intercut old 4:3 interlace footage, but you want to zoom into the 4:3 stuff to make it 16:9 anamorphic to match the rest of the programme; interlace shot footage will cause havoc.
Interlacing also causes issues for watching DVDs on computer monitors. LCD televisions have all sorts of jiggery pokery to cope well with interlaced footage, but computer LCD’s do not.
©2009 Nigel Cooper