High Definition Frequently Asked Questions

What is the difference between Interlaced and Progressive formats?

Basically, interlaced is like TV and progressive is like film or 50i is PAL, 60i is NTSC and 24P is film. TV uses interlaced scanning to conserve bandwidth. Each frame is displayed on the screen twice in what is called a pass or field. With each pass the odd and then even lines are scanned in a 1/50th second. A complete frame is scanned 25 times per second. With a progressively scanned system the entire frame of pixels is conveyed every 1/50th second at 25 times per second. In the US the lines are scanned every 1/60th second.

1080i is an interlaced format consisting of 1080 active lines with a 16:9 aspect ratio and the format uses square pixels.

720P is a progressive format and it consists of 720P active lines, again it uses a 16:9 aspect ratio and square pixels.

Is HDV true 16:9?

Yes, it uses oblong pixels rather than square to create the 16:9 Aspect Ratio. This means that it stretches the horizontal pixels to fill the frame and records 1440 x 1080 rather than 1920 x 1080. This is purported to be acceptable to broadcasters, similar to the PDX10.

Can you shoot in 4:3 mode on HD?

No. The format is native 16:9 and would result in severe cropping if viewed in 4:3 aspect ratio. If broadcast it would need to be letterboxed to view in 4:3.

How does the progressive Cineframe 24 setting in the HVR Z1E work?

It is very rudimentary but what it does is interpolates or copies half frames to give the effect of a film look. This will result in errors particularly when editing and a loss of resolution.

What is the difference between HD and SD lenses?

The main difference between HD and SD lenses is the quality of the glass components. Due to the high resolution of HD, up to four times greater than SD and the fact that HD has a 16:9 aquestionst ratio only, any flaws in the optics will cause aberrations to show up. The high resolution of HD means even a slight out of focus area is detectable due to the depth of field being shorter than in SD. This is useful if trying to emulate the shorter DoF of film lenses.

Why does progressive look 'juddery' through the VF and does this clear up when recorded to tape?

The progressive frame rate looks juddery through the VF (viewfinder) because the VF is an interlaced device and cannot cope with a progressive image. This is also replicated on most monitors as they are primarily designed around an interlaced image, some HD ready monitors are able to cope by scanning the image at twice the speed of conventional monitors but when shot in 25P it is hard to create the same motion blur of film. You can emulate this effect by using a variable shutter speed of 1/48 in 24P mode on the 900.

Can you use prime lenses with HD camcorders?

Yes, you can use prime lenses with HD camcorders. More commonly used where using video instead of film. Some of the benefits being the similarity to film lenses, T stops rather than F stops, consistent colour temperature and minimised focus breathing.

Why would you use a Progressive format?

A progressive format is used to create a filmic look. It is most commonly used when shooting HD for cinematic release (Collateral) or TV drama productions (MIT).

Does HDV record full resolution HD?

Yes, it records 1080 lines but it is seriously compressed at 31:1 and writes at 25Mbps and records 1440 x 1080 rather than HDCAM which is 5:1 and writes at 184 Mbps and records 1920 x 1080 lines.