PAL, Progressive Scan, and Video to Film transfers go well together like chocolate and peanut butter, however, like the classic Reeses commecial, sometimes the collision can get a little messy. For filmmakers shooting DV features and shorts, many post facilities suggest origination on PAL using a camera capable of progressive scanning. Why is this so? Does this wisdom extend to NTSC? And what should we watch out for? Progressive scan and movie mode appear in lots of camera literature touting it as the answer to something. What was the question in the first place?
When it comes to DV, many choices need to be made in terms of camera, format, and post-production options. So many options need to be weighed during preproduction, especially if converting to high def or doing a video to film transfer is on the horizon. In the good ” ˜ol days we knew the final destination of our films and the options were few… today our films can be converted to many different formats as they make their way to the audience… video streaming, film projection, broadcast, DVD, high definition projection, and pan galactic distribution (well, maybe not this week). How do we make sure our production decisions don’t get us in trouble during post-production?
First and foremost, when shooting digital video, the post facility you are working with is an integral part of the medium, whether it’s your own Macintosh at home or a professional post facility. Given so many options and destinations, it’s good to have a roadmap.
Consider for a moment that film is a very complex medium (layers of silver halide emulsions and complex chemistry at work) requiring simple mechanical devices to manipulate. Video, on the other hand, is a simple medium (metal particles on a tape holding magnetic impressions) requiring complex electronic devices to manipulate. With film, the fundamental characteristics of the medium are locked in the film itself. With digital video, there are fewer limits as to what can be done with the collection of bits representing the sound and images. The only limitations I can see are imagination, computer processing time, and data storage. Richard Linklater’s Waking Life comes to mind. Life is good in the digital domain. The dance of bits is relatively inexpensive to choreograph and perform, however, the cost of “moving over to the other side” can be steep. A quality digital video to film transfer will set you (or hopefully, your distributor) back anywhere from $12,000. to $40,000. for a feature length project. The decisions made in pre-production and production will either delight or haunt you in post-production. I prefer delight.
If the “film look” is a desired goal (and it need not be), we need to address two key aspects of what makes film look like film: the frame rate (24fps) and non-interlaced frames (progressive scan in video terminology). There are other characteristics, and this is the topic of a complicated debate, but for now we shall limit our discussion to frame rate and progressive scanning. At the high end, the new generation of High Definition cameras like Sony’s F-900 and Panasonic’s V27 “Varicam” offer progressive scan and 24fps acquisition, offering filmmakers the best format for origination with the ability to elegantly translate to any other format now and in the future. 24fps material is easy to convert to all of the delivery formats in use today without serious artifacts, and progressive scanning is free of interlace artifacts. While this may be ideal for projects with generous budgets (F-900 and V27 camera packages go for about $1,000. per “day” ), is there a lower cost alternative that comes close for the DV filmmaker? The answer is a qualified yes.
The solution lies in shooting PAL with a camera capable of progressive scanning or something coming close to it. Space does not permit a detailed technical explanation of why 25/24fps and progressive scan is such a favorable acquisition option, for a more detailed discussions see the notes at the end of this article. If you are shooting with a consumer camcorder, PAL offers you the closest thing to the new high-end 24p solutions at an affordable price point. Matching the frame rate of film goes a long way to creating a filmic image. Resolution in and of itself is not what makes or breaks a movie (I can hear the groans in the balcony). When your PAL project is transferred to film, the best image is obtained by using the frames in the PAL video (25fps) in a one to one relationship with the film frames (24fps), which results in perfectly smooth projection but does entail one minor problem: a 4.166% reduction in speed. This will require audio pitch correction for the audio track. Motion will be 4.166% slower in the final film. I actually like this effect, but again, it’s an aesthetic issue to be considered.
Standard NTSC and PAL video is interlaced. Interlace refers to each frame of the video actually consisting of two video fields, each containing the odd or even lines of the image. During image capture the camera alternates outputting the odd and even lines . The result is a temporal shift between the odd and even fields. Computer monitors and some of the newer video formats are progressive: the entire contents of each frame is recorded at the same time. That’s why computer monitors are so crisp compared to television. Sit 12 inches away from a TV monitor sometime and look at scenes with motion. See the “serrated edges” in the image? Now pause a high motion scene. More “serrated edges” will be evident. That’s what happens when every other line is temporally displaced. We don’t seem to mind interlacing when we are watching television at a normal viewing distance, however, interlace causes havoc when it comes time to convert interlaced video to a different standard or to film which will be projected on a large screen at a different frame rate. All this interlace business goes away if we shoot with a camera that supports progressive scan.
Beware, not all progressive modes are the same on consumer cameras. Canon’s progressive scan (“frame movie mode” ) on the PAL version of the XL-1 and its ilk runs at 25fps yet interpolates only a percentage of the frame from each scan. The line averaging process results in an image that is somewhat softer than an interlaced image of the same scene, however, it’s sharper than looking at a single field and yields very nice results when the PAL video is transferred to film one to one. Sadly, the progressive scan modes on the Sony consumer camcorders I’ve used record at 15 fps, good for stills but results in jittery motion. Not good. For the best consumer level progressive scan I suggest shooting with the Canon cameras.
Here is where post-production can get complicated (and expensive if you are “doing it right” ). Slowing down the audio in the conversion from PAL’s 25fps to Film’s 24fps is not a big deal if you only do it for the production dialog. 4.166% happens to be just within the bounds of the ability to do pitch correction without serious artifacts. You certainly don’t want to do this to your entire final mix. Doing the slow-down of the audio and correcting the pitch of a final mix will result in various artifacts that will have your sound mixer screaming. On the other hand, you will be safe with audio pitch correction if you only slow down and correct the production dialog.
So now we have a movie shot in progressive scan PAL. How does this all work in post? Does this make things unbearably complicated? Avid’s Media Composer and Apple’s Final Cut Pro can edit PAL materials, but what about the sound? I recently turned to Alfie Schloss and Christian Zack at Tape House Digital Film in New York to help me sort out the postproduction workflow. The key is to follow what I’ve coined as the “Pseudo 24P Post-Prodution Chain” :
This method allows you to do your post-production using an affordable editing system and sound editing tools on the desktop. The only dependence on an outside post facility is to do the slow-PAL tape transfers from your PAL edit master for sound editing and the sound mix. These tapes also come in handy as an NTSC version of your film. While your image will be slowed down, the audio will be in real-time,” making your sound post simple to do with NTSC reference tapes.
This 25 fps PAL becomes the “low budget filmmaker’s alternative” to the much touted 24P video production standard. The beauty of this scheme is you are not married to doing an expensive $40K transfers if not needed. After your sound mix, you can screen and shop around the NTSC version of your project. You will end up with versatile masters that are easily converted to any other format. If you want to shoot and post on video with the ability to do an excellent transfer to film, shooting in the PAL standard with a digital camera with a progressive scan option is the route for the highest quality final results.
I would not undertake PAL post in an NTSC country, however, without a post-production supervisor who understands this process and a producer who has properly budgeted the approach. The time for surprises is pre-production, not post-production. It breaks my heart to see excellent films stall for the lack of funds in post-production. Shoot with creative abandon… budget with restraint and caution. On the other hand, if you do not want to be dependent on an outside post facility, and you are working in a country in which NTSC is the broadcast standard, by all means, stick with NTSC. If you don’t care about a few motion artifacts and a perfect film transfer is not a high priority, NTSC is the ticket. Remember when you are shooting in NTSC to avoid the progressive mode unless you specifically want to use it as an “effect.” It can look terrible when transferred to film. As with any deviation from “the norm” I suggest you experiment or trust the judgment of an experienced cinematographer who has done several DV to film projects you have seen with your own eyes.
For more detailed information on frame rates and progressive scanning see Adam Wilt’s excellent discussion “Frame mode, slow shutters, and ” ˜the film look’” on his web site. Special thanks to Alfie Schloss and Christian Zack at Tape House Digital Film for their valuable insights during the preparation of this article. Tape house provides video postproduction services and video to film using an ArriLaser film recorder.
This post is based on an article that was originally published in the New York Film & Video Monitor,Vol. 7, No. 4 (January / February 2002).