What's the difference between high definition (HD) and standard definition (SD)?

The current SD picture is made up of 575 visible lines. HD consists of up to 1080 lines, giving far better picture quality. Sony's HDCAM format records 1080 lines. Panasonic's DVCPRO HD format records 720 lines (some cameras up-convert to 1080, but still have a 720 line CCD). Standard definition (PAL or NTSC) has been recorded and transmitted by interlaced scanning. High definition offers the opportunity for progressive, as well as interlaced scanning.

The implication of the increase in resolution is that focus is much more critical, as is attention to detail in the frame when shooting. It is recommended that an HD monitor is always used on location when shooting HD for checking focus and the content of the frame.

What's the difference between interlaced and progressive scanning?

There are two ways a high definition picture can be constructed - progressive (p) or interlaced (i). Each system gives a different look, progressive looks more like film and interlaced gives a familiar video look.

An interlaced picture is separated into two sections called fields. The first field is the odd lines - 1, 3, 5 etc, and the second field is the even lines - 2, 4, 6 etc. These two fields are then combined to make a frame. A progressive picture is made up by scanning the lines in order, one after the other - 1, 2, 3, 4 etc. So instead of individual lines being scanned separately and then re-built as with interlace, each complete image is scanned in an instant.

Can I shoot interlaced and convert to progressive?

The answer is 'yes but why?!' This process is equivalent to field doubling in SD. Some vertical resolution will be lost as a result. Therefore, would always recommend careful consideration before shooting, as taking the wrong acquisition route can be costly and difficult to correct.