A great director once asked, “To Interlace or not to Interlace? That is the Question. Whether ’tis nobler in the mind to capture slings and arrows of sporting events clearly, or to make beautiful film-like pictures against a sea of blur…”
Well, maybe that wasn’t exactly what he said, but it went something like that. In any case, the question is asked a lot: Should I shoot in interlaced or shoot progressive instead? Most people have learned that video shot progressively has a film-like look and that interlaced looks more like news. Well, it’s not that simple. Both types of recording have a place and a time, and to use one over the other is asking for some real drama. But make a choice you must. So in order to understand which way to shoot, you must first understand the difference in the way the video is laid down on the tape.
Progressive
Let’s take the progressive image first. Progressive, also known as the letter “p” (as in 24p or 30p), is laid down line by line onto the tape in sequential order (i.e., lines 1, 2, 3, 4, 5, etc.) until it fills a frame. Then it returns to the top and repeats, thus drawing one complete uninterrupted image. Why does this matter? It matters because each frame is a complete picture, and that allows very clear freezes. It also means that it takes longer to lay the image down. This means more movement can happen while it is scanning, potentially causing a softer image. Some non-techie types might be looking at each other at this point and asking, “What do you mean? Video is recorded some other way – we don’t shoot one image at a time?” The answer is NO. We don’t. We shoot two half-images called fields. “We” – the U.S., that is – a long time ago decided to record images in a faster way and called it interlaced.
Interlaced
Interlaced, also known as the letter “i” (as in 60i or 1080i), was chosen for a lot of technical reasons that have little to do with how we watch and shoot television today, but nonetheless we are stuck with it, unless you’ve chosen a progressive HD format. The outcome of this decision left us with a very crisp image that is laid down in an alternating order. This time the lines are scanned 1, 3, 5, 7, 9, etc. into what is called a field. When the scan returns to the top and repeats (now scanning the even lines), the two fields are then woven back together to make a full-frame image, hence the name interlaced.
What makes this technique different from progressive is that it reaches the bottom of the frame in half the time. This means that, if something is moving very fast across the screen, say a runner or a car, interlaced will deliver a crisper picture, much like a fast shutter speed on a still camera. Keep in mind we are not talking about engaging the shutter switch, which can increase the speed upwards to 1/1000th of a second OR shooting at a faster progressive speed like 60p, which a lot of newer cameras now have available as an option and which we will discuss in a minute. This is just plain old interlaced. However, just recording faster doesn’t make it better. The downside of an interlaced capture is the freeze frame. The interlaced frame, remember, is really two pictures/fields put together to make a full image. So, if the subject is moving fast, you may have two different images in two different locations in the same frame. This causes a jumping effect called jitter, which, I think, really looks like someone with a bad caffeine rush! I do find it ironic, however, that interlaced delivers a much cleaner image overall for sporting-type events, but is worse for freeze-frame. But that is the case. Progressive has the same issue, but in reverse. Fast-moving images can blur, because the scan takes longer to complete, but because it is a full frame, there can never be jitter in a freeze-frame image.
Other Concerns
There is one other thing that I should mention for those of you wishing to shoot progressive and still do sports, and that is HD. You can now shoot modern-day HD in very fast progressive speeds (60p), thus capturing very fast images, yet still maintaining the clear freeze frames. To me, this is the best of both worlds, but you pay for it. You might also want to try engaging your shutter switch and increasing your shutter speed, by shooting at 1/250th up to 1/1000th of a second. This effect breaks your image into even shorter time intervals per frame. When slowed down, this makes for an awesome slow motion. Be aware, though, high shutter speeds require lots of light. So be sure to try this on a sunny day. One other great trick is to shoot at 60p but play back at 24p. Now you are talking professional slow-mo. Try this sometime. You will be amazed!
Whew! OK, so now do you get the picture? Or should I say frame? Progressive and interlaced are merely choices, not hard and fast rules. Unless, of course, you’re working for someone else. Then be very sure that you ask which format is wanted. Many production companies and TV stations have a look that they adhere to, regardless of what they are shooting. To shoot the other might create headaches for their setup and could possibly lose you their future business.
I find that I like the soft look of progressive for most of my pieces, because I rarely shoot sports.
But if you are doing a hunting show or capturing a football game, I would recommend that you shoot in interlaced. Before you shoot, ask yourself these questions: “What type of story am I telling? Which format best suits my needs? Am I shooting a slower-moving piece that requires warmer, softer images, or do I need to see lots of detail when the dagger falls?”
Good luck in finding your direction, whether progressive or interlaced!
Michael Reff is a Senior Photographer for Turner Broadcasting System, Inc.
