Grading the Formats: How They Stack Up - and Why

Ever wondered which format was best? Ever wish you had a report card comparing key areas of camcorder performance? Wish no longer.

In the next few pages, we’ll see how the popular consumer video formats stack up in three important areas: video quality, audio quality and susceptibility to generation loss. To see the grades for each format at a glance, check out the "Report Card" sidebar.

Video quality

When it comes to camcorder performance, the quality of the images it gathers may be the most important test of all. How well a camcorder scores in the area of video quality depends largely on the format it uses.

Boil it down and the video quality of a format is directly related to the quantity of information it can pack onto the tape. More information translates to better detail, which, makes for better images. We quantify a format’s ability to record detail by measuring how many light-to-dark transitions it can record across the screen. This is called a format’s horizontal resolution.

The formats that record the least amount of video information are 8mm and standard VHS. These formats usually deliver just over 200 lines of horizontal resolution, which is about one-third less detail than you get from a normal cable TV channel. They are best used for recording non-edited family events or movies recorded from TV for your video library at home. 8mm and VHS can look pretty good but they don’t score much better than a C on our video quality test.

When crafty engineers figured out how to pack more information on the same size tape, the Super VHS (S-VHS and S-VHS-C) and Hi8 formats were born. These "high-band" formats record almost twice as much video information as 8mm and standard VHS. Good S-VHS and Hi8 camcorders can deliver roughly 400 lines of horizontal resolution. The S-VHS, S-VHS-C and Hi8 formats are good for the acquisition of footage to be edited in a mid- to high-end post production environment, and S-VHS is ideal for the mastering of a final edited project. These formats get a solid B on the video quality report card. The final format taking our video test is DV, the all-digital newcomer to the consumer video class. Instead of recording a complex (and error-prone) analog signal to represent the image, DV converts picture information into a string of simple numeric codes of ones and zeroes. It then compresses the digital information to pack more of it onto that skinny little DV tape. The end result is more picture information (and more detail) being recorded than with any other format. Because it’s digital, DV doesn’t suffer from as much video noise as the normal analog formats. This makes it the perfect format for acquisition, particularly for the producer who needs the very best quality video for that project that pays. With the potential to record over 500 lines of resolution, DV scores a solid A in image quality.

Sound quality

If the image is the most important factor in the quality of a video, sound is the second most important factor. A video that looks good and sounds bad is a bad video. The format you use can make a significant difference in how your video sounds as well as looks.

As with video quality, audio quality is directly linked to how much sound information a format can store. Sound quality ranges from ho-hum to excellent depending on format and the type of audio tracks in use.

At the bottom of the curve are the linear audio tracks found on the VHS and S-VHS-family formats. These miniscule strips of tape don’t hold much audio information and the resulting sound is usually noisy and lacking in fidelity. The linear track is also usually mono. Grade: C-.

Thanks to the hi-fi stereo audio found on many VHS and S-VHS-family camcorders, these formats enjoy a higher than average audio grade. Hi-fi stereo audio sits underneath the video on the tape and delivers sound quality to rival that of a compact disc. Though you can’t replace hi-fi audio without erasing the video (and vice-versa), hi-fi stereo earns an A- for very good sonic quality.

From the beginning, 8mm and Hi8 formats have delivered respectable sound quality. These formats embed their AFM (Audio Frequency Modulation) audio in with the video (much like the hi-fi system mentioned above), making it impossible to change one without erasing the other. Though AFM audio was originally mono, most 8mm and Hi8 camcorders now offer stereo AFM sound. AFM audio is roughly as good as a strong FM radio station, earning it a B-.

Some Hi8 units boast stereo digital audio in addition to the normal AFM tracks. The main advantage of this feature is the ability to erase and re-record the digital audio without affecting the video. Sound quality of these PCM (Pulse Code Modulation) digital tracks is slightly better than the AFM tracks, scoring a respectable B+.

This brings us to the DV format. As with video, the DV format converts sound information to a string of numbers. There’s a set amount of space allocated on the DV tape for audio. The DV format can divide up this "bit pool" in two different ways. One way is a two-track mode that splits the pool in half to record a pair of stereo tracks. The other is a four-track mode that splits the pool into quarters, giving you four audio tracks to record and dub to. Because the two-track mode stores more information for each track, sound quality is grade-A. The four-channel mode doesn’t have quite the clarity of the two-channel mode, earning it a B grade.

Generation Loss

As videographers, we often edit and copy our videos before showing them to others. This process usually involves connecting a camcorder and VCR (or two VCRs) together to transfer audio and video signals from tape to tape. If you’re not doing your copying or editing digitally, you’ve probably noticed that the quality of the newly recorded tape rarely matches that of the original. Do a copy of a copy, and things only get worse.

We call this generation loss, and it’s the tragedy of analog recording. Part of the problem is noise, which pollutes the signal a little more with each generation of tape. The other factor is the inevitible loss of detail and crispness that happens when copying. Generation loss isn’t just limited to video, sound can get noisy and indistinct as well.

In general, the better the quality of the format, the less generation loss you’ll notice with each copy. This explains why VHS, VHS-C and 8mm suffer the worst generation loss of all the formats. These formats often reveal considerable degradation after just one copy. More suitable for casual shooting than serious editing, these formats don’t fare so well on the generation loss test. Grade: D.

Remember those high-band formats that deliver better image quality than their standard brethren? It turns out they’re less susceptible to generation loss as well. Though S-VHS, S-VHS-C and Hi8 do exhibit some generation loss, they have more detail and less noise to start out with. Using the S-video jacks commonly found on these formats also helps to deliver a cleaner copy. When the generation loss grades are tallied, S-VHS, S-VHS-C and Hi8 score a B-.

The DV format, has a rather
unique capability for copying and editing. If you transfer your
audio and video between DV units digitally, the recorder lays
down digital clone of the playback tape. This means almost no
generation loss. This is one of the greatest advantages of the
DV format, earning it an A grade on our generation loss test.
Even if you make non-digital copies of your DV tape with S-video
jacks and cables, the impressive quality of the DV format has
such a high resolution to begin with (500 lines depending on the
camcorder) the effects of generation loss are kept to a minimum.
A dub on S-VHS or Hi8 would essentially be the same as original
S-VHS OR Hi8 footage.

Graduating Class

Because of its digital technology, the DV format passes our test with top honors. Hi8, S-VHS and S-VHS-C are a close second, delivering good results for most consumer applications. VHS, VHS-C and 8mm, though not optimum for editing, are good basic formats.

Remember, it’s up to you to decide which format makes the grade.

Sidebar: Format Isn’t Everything
Though format is the largest factor affecting a camcorder’s performance, there are other forces at play. In some cases, an "inferior" camcorder may shoot better video than one using a higher-quality format. Here are some other factors to consider:

  • quality of tape
  • quality of optics
  • quality of CCD sensor
  • number of CCD sensors
  • electronic design
  • cleanliness of lens
  • cleanliness of video heads
  • wear/damage to video heads or transport

-LA

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