Tom's Hardware > All Reviews > Special > Miscellaneous > Quick Guide to 15 HD Camcorders

Format/Compression, CCD Size-Resolution And Low Light

03:47 - Monday 5 February 2007 by Chris Iannicello

HDV

This is the standard compression system used for high-definition video onto conventional MiniDV tapes, and supports either 1280 x 720 progressive (720p) or 1920 x 1080 interlaced (1080i) resolutions. HDV uses MPEG-2 compression, and the bit rate after compression is 25 Mbps, which results in very good video quality. MPEG-2 has been known to be susceptible to block noise and errors, but the high bit rate of HDV reduces the risks of these types of issues.

Some "1080i" HDV camcorders have a resolution of 1440 x 1080, while the resolution of others is 1920 x 1080. The maximum resolution after compression onto MiniDV tapes is 1440 x 1080. So any HDV camcorder with a resolution of 1920 x 1080 will be down-converted to 1440 x 1080 to fit onto the MiniDV tape and then up-converted to 1920 x 1080 when displayed.

A camcorder with '24p' resolution mode can record video at 24 progressive frames per second (films/movies are filmed at this rate) in addition to the traditional camcorder video rate of 60 interlaced frames per second. Despite having to be converted to 60 interlaced frames per second when recording onto HDV/MiniDV tapes, the 24p mode should still provide a distinct, film-like look compared to recordings shot in regular 60i mode. This feature is normally found in higher-end camcorders.

AVCHD

This is a new compression system used in DVD and HD-based camcorders which allows the recording of high-definition video onto existing DVD media. AVCHD uses MPEG-4/H.264 compression, which is more efficient (allowing longer recordings onto a smaller amount of disc space) than the MPEG-2 compression used with HDV. Although there are mixed opinions, many experts claim that the video quality of HDV camcorders is superior to current AVCHD-based camcorders, which use a bit rate of 12-15 Mbps (compared to 25 Mbps for HDV), resulting in picture noise and other artefacts in some models.

However, unlike HDV, AVCHD is a dynamic format that can be improved over time as the AVCHD standard has a maximum claimed bandwidth of 24 Mbps. Also, AVCHD does not have the resolution limitations of HDV, which means it can support a full 1920 x 1080 interlaced resolution compared to the unconverted 1440 x 1080 resolution of HDV. Although there are no models currently utilizing this full resolution, this should provide another significant advantage over HDV when AVCHD camcorders with full 1080i resolution become available. This and the superior MPEG-4/H.264 compression lead many experts to believe that AVCHD will eventually surpass HDV/MiniDV in video quality.

CCD Size/Resolution

CCD stands for "charged-coupled device." CCDs are sometimes referred to as "image sensors." Generally speaking, the larger the CCD (or number of CCDs) and/or the larger the resolution on the CCD(s), the better the overall video quality is. Camcorders either have one CCD or 3 CCDs. Three CCD models usually provide increased colour fidelity and saturation.

Low Light

Lux is a light measurement equal to one lumen per square meter. Every camcorder has a lux rating, which equates to how little light is needed to record an image. So the lower the lux rating, the better the camera performs in low light. However, there is no standard method of producing this rating from brand to brand, so real-world testing and/or reviews are a much better indicator of low-light performance.