• What’s with all these HD formats and frame rates?
• What ingredients make the “film look”?
• Why shoot progressive instead of interlace?
• Why shoot tapeless?
• What does shooting in “Native” mode mean?
• What’s the best way to capture smooth motion?
• What is the best way to shoot slow motion?
• How does DVCPRO HD compare to HDV, AVCHD or XDCAM EX?
• Why shoot HD if the project is being distributed in DVD or over the internet?
What’s with all these HD formats and frame rates?
It’s true, when it comes to HD standards, there is no standard. When talking about network television(and cable networks), there are two HD resolutions, 720P and 1080i and P. Within those resolutions, there are multiple frame rates. Even if a network broadcasts in 1080/60i, it doesn’t mean that the field acquisition format can’t be 1080/24p or 30p. The reason to shoot with a 24p frame rate is for a more “filmic” look. The motion is more like a movie vs. a soap opera or sporting event. It will make drama look more like we expect drama to look like. However, fast pans will have a stuttering effect, motion will not looks as smooth as 60i. This is true for 720/24P or 1080/24P. 30P is a little smoother and has the advantages of progressive scan vs. interlace. 720/60P will offer the smoothest, most detailed motion, superior to 1080/60i. There can be camera sensitivity differences between these frame rates, especially when applying a 180 degree shutter to 24P or 30P to minimize smearing. Each project type and style will dictate the field acquisition format, no matter what the mastering format requirement is.
What ingredients make the “film look”?
Many times a project strives for the “film look” vs. the normal broadcast news/sports look that video cameras normally provide. The “film look” has many ingredients, including filmic, soft large source lighting, 24 frames per second frame rate, cinematic blocking and editing, film gammas and post-production color and grading treatments, lens or post-production diffusion, reduced electronic detail, shooting more wide open or using a 35mm Cine adapter with35mm lenses to get selective focus due to shallow depth of field, all these things contribute to the film look. Additionally, less zooming, more camera movement due to a dolly or jib or slider contributes to the cinematic look and of course the widescreen aspect ratio is a big factor as is high definition. Film look is also not depending upon fancy transitions or flying graphics, but more on cuts and close-ups and of course, good story telling.
Why shoot progressive instead of interlace?
Because we live in the 21st century and virtually every video display we watch these days is progressive, not just our LCD computer screens anymore, which were always progressive scan. When television was invented, interlace was necessary because the Cathode Ray Tube, CRT, picture tube monitor couldn't produce a full screen of video every thirty times a second. The phosphors in the CRT would lose their "glow" too quickly and thus create a lagging and uneven brightness in the picture. As the "gun" that would "draw" the image from the left to the right, in a "Progressive" mode it would not be fast enough to keep the entire screen "on" to produce a smooth full motion television signal. The fix was to create two "fields" of half the total resolution each, to create a whole useable picture signal. Each field had 262.5 lines for NTSC and worked in an Odd and Even mode. The CRT Gun would draw the Odd Field first, starting at the upper left with Lines 1 ,3, 5, 7 etc, then scan the Even Lines, 2, 4, 6, 8 etc. Persistence of Vision helped make this TV trick work just as it does with Film. Two fields for every one frame, 60 fields a second or restated as 30 Frames a second. With the advent of better CRT materials and eventually LCD, DLP and Plasma technologies there was no reason to shoot in an interlace mode. The progressive images are smoother, resolution is greater and all without the many artifacts associated with interlace images. Some think of 1080/60i as having higher resolution than 720/60p, but the reality is that the vertical resolution of a 1080/60i image is only 540 lines. All 720 frame rates are progressive, 1080 is available in progressive or interlace, the latter being 60i only for the U.S. There is very little reason to shoot in interlace, even if mastering to 480/60i or 1080/60i. Every LCD and Plasma display is fixed pixel, progressive scan. Progressive footage is also very desirable when doing complex compositing and keying in post production.
Why shoot tapeless?
Tapeless file based recording works very well with non-linear edit systems because they are all computer based. The ingest process from tape is a slow realtime workflow, renting a DVCPRO HD VTR by the hour or day is expensive, while file based clips in P2 .mxf or Quicktime .mov formats can be transferred onto a hard drive on-set or in the edit room in a quarter of the time. The files are divided into clips, so finding the beginning of new scenes is fast and easy. Tape transports are larger and mechanically more complex than solid state P2 cards or hard drives, so are less reliable, more maintenance intensive and susceptible to drop outs. File based recording is the future of location shooting, not tape, just as tape is no longer used in audio recording. These clips are edit ready, saving time and money.
What does shooting in “Native” mode mean?
When recording onto P2 cards or on-board hard drives for file based clips vs. onto tape, it is possible, when shooting 24 or 30 frames per second, to record only the actual 24 or 30 frames instead of redundant frames needed for tape that requires 60 frames per second. Those redundant frames are flagged and then tossed out by the non-linear edit system. Native frame rate modes save those steps, offer more efficient use of P2 card or hard drive space, recording a bit rate of only 40Mbps for 24P Native vs. 100Mbps for 24P, allowing for 2.5 minutes per gigabyte vs. only 1 minute per gigabyte. This much lower bit rate is desirable because record capacity is 2.5X larger and transfer times are shorter.
What’s the best way to capture smooth motion?
When shooting 24P or 30P, some people object to the more stuttery motion vs. 60i. It’s true that the lower the frame rate, the less smooth pans and motion are. However, if smooth motion is desired, the better alternative to 60i is 60p. 60 progressive frames is superior to 60 interlace fields for many reasons. No interlace artifacts like stair stepping on diagonal lines, interline twitter. Resolution is better, motion is smoother. 720/60P has superior vertical resolution to 1080/60i.
What is the best way to shoot slow motion?
With tape based Panasonic DVCPRO HD cameras such as the HDX900, 720/60P offers the best, smoothest, non-smearing slow motion imagery. It can be slowed down within the 60p time line or dropped into a 30p or 24p timeline for a more filmic look. With P2 based DVCPRO HD cameras such as the HPX170, it is easy to have variable frame rates over 24p, such as 48 fps and 60fps, all done in camera, and allowing simple playback in slow motion so there is no guessing while shooting. There are no cameras offering 1080/60p, so 720/60p remains the best slow motion format.
How does DVCPRO HD compare to HDV, AVCHD or XDCAM EX?
The Panasonic DVCPRO HD format has been around for awhile. It is an established, proven workflow that allows grading and color correction and little rendering time. Some of the newer codecs such as HDV or the newer AVCHD or XDCAM EX codecs are more efficient because they are optimized for low bit rates. However, unlike DVCPRO HD, which runs at 40-100Mbps, with I-Frame and 4:2:2 color space, these lower cost codecs are running at anywhere from 18-35Mbps, have lesser 4:2:0 color space and are Long GOP frame structure. They are more computer processor intensive, and don’t have as much flexibility in grading, color correction and keying. Editors prefer I-Frame codecs, where each frame is unique vs. Long GOP frame structure. The Long GOP frame structure will also result in much longer renders in post production that will actually add to your budget.
Why shoot HD if the project is being distributed in DVD or over the internet?
Shooting in HD offers many advantages, such as; longer shelf life in case of eventual HD distribution. The capability of “punching in” to a closeup, so that one pass of a scene shot in HD but shown in SD can have two focal lengths. Oversampling, meaning more resolution to derive a master from, usually means better quality. A 35mm movie that ends up on DVD usually looks much better than a DVD shot with a SD NTSC camera. Many websites, like Vimeo and even YouTube are now offering HD over the internet these days, so shooting on SD could be limiting and put the project at a disadvantage.