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Pick a Format Making sure a recorder can do what you want it to is to some extent a format question. To give you an easy way to compare the formats, we've listed some key features in the table below. Note that DVD-RAM differs significantly from the other rewritable formats, DVD+RW and DVD-RW.

Here are some things to keep in mind while checking out the table, which applies only to standalone DVD recorders:

• Every new generation of recorders seems to include features (especially in the DVD-RW area) that were unanticipated when the formats were introduced. For example, Sony claims that its RDR-GX300 recorder (due in July) not only records on +R/RW and -R/RW discs, but also lets you use DVD-RW discs for some of the simultaneous record-playback functions you used to need DVD-RAM or a recorder with a hard drive to perform.
• Recorders with built-in hard drives let you use DVD-R and DVD+R discs to do the kind of editing that's usually only possible with the erasable formats. That's because you do the editing on the hard drive before burning the video to DVD. And a hard drive lets you easily make multiple copies of something you've edited while maintaining sound and picture quality.
• Some recorders are better than others at taking advantage of a format's capabilities, so read the fine print in the owner's manual to see if a model behaves as listed in the table. You can download the manuals for most recorders from the manufacturers' Web sites.
• Features that seem minor can turn out to be important once you start using a recorder. For example, adding chapter markers after recording a program - so you can skip commercials without editing them out - is impossible with certain formats.
• If you want to move discs between recorders, or between a recorder and a computer, pay attention to the rows in our table concerning finalization. Finalization lets you play DVD-R/RW or +R/RW discs in other decks, players, and computers, but it prevents further recording on write-once discs. It's not relevant to DVD-RAM.

PDF: How the Recordable-DVD Formats Compare Image Is EverythingThe picture quality of recent DVD recorders is about even all around, so how good the image will be is mainly a question of which recording "mode" you select. Recorders have multiple modes, equivalent to a VCR's tape speeds, that offer a tradeoff between recording time and picture quality. But the difference in quality between the "best" mode (which gives 1 hour per disc) and the "worst" mode (6 or 8 hours, depending on the model) is greater than between a VCR's SP and EP speeds.

The 1-hour mode delivers picture quality about equal to that of a DVD movie, and many decks come close to this level of performance even in their 2-hour modes. It's when you go beyond 2 hours that degradation becomes noticeable. Horizontal resolution is cut in half because the recorder captures only every other horizontal pixel. And various "artifacts," or distortions caused by MPEG encoding, start to appear, especially around the edges of objects.

The most common problem is "blocking" (or "macroblocking"), in which areas of the picture appear to be broken up into small squares. The second most common artifact is "mosquito noise," which makes objects with sharp borders look like they're surrounded by swarms of mosquitoes. This often accompanies the movement of these objects and can change shape as the noise passes in front of other objects. In both cases, the picture looks less sharp overall - rougher or grittier.

For modes with recording times of 6 or more hours, most recorders encode every other vertical pixel, cutting vertical resolution in half as well. With horizontal and vertical detail significantly reduced and encoder artifacts going full tilt, the picture looks worse than at a VCR's EP speed. The blocking and mosquito noise are more intrusive than the snowy (noisy), color-smeared look of slow-speed tape. And, on some machines, the movement can look jerky, too.