HDV and the disemination of mis-information
Despite the rapid and broad uptake of HDV as a viable, functional and flexible HD format, it is still surprising how widespread and even deeply entrenched are the myths and mis-information about what HDV is, how HDV works and how good HDV quality can be? Many of these myths stem from little more than deeply engrained old-school mentalities that fail to move with times, others just seem to come out of a profound lack of Real technical knowledge.
This much published, much quoted, much referred to article illustrates the issue. Entitled
What I've learned about HDV it is a set presumptions and issues with a very high degree of technical fallacy. Here's some examples taken from the article -
This GOP method of compression means that HDV is not accurate for timecode or frames when capturing or outputting.? This is just true in any real-world practice.
HDV uses extreme color sampling, resulting in very poor color keying, color correction, or compositing results.? Yes 4:2:0 is heavy sub-sampling but its the same as DV (PAL) and HDV and DV can be very well keyed and composited, and have been done so for many years. Its simply a myth that you cant key HDV, uncompressed might certainly key better but this doesnt mean that 4:2:0 cannot be keyed. As for colour correction, the fact that HDV footage from very small HDV cameras such as the Sony Z1 has been used in
Letters from Iwo Jima, Flags of our Fathers, 28 days later and 28 weeks later, episodes of
CSI Miami (including their title sequence) episodes of
JAG and countless other productions as well as having been intercut with HD and and 35mm film seamlessly and undetectably, just paints this argument into the un-useful catagory.
HDV is enormously compressed, creating the possibility of significant motion artefacts when the camera is moved, or zoomed, quickly.? Motion artefacts can happen on any camera and have much more to do with light and shutter speed than compression. Douglass Spotted Eagle's death defying skydiving footage from a tiny Sony A1 HDV camera strapped to his head and moving at hundreds of feet per second, and which looks absolutely pristine in clarity and motion, dismisses this much persistent myth.
HDV can only use Print to Tape, not Edit to Tape, due to needing to conform the image prior to output.? My god, who does Edit to Tape anymore? Are we living in the dark ages? get a bigger hard drive!
The HDV image is 1440 x 1080, which does not precisely match either the 720p or 1080i format? Anamorphic Pixel Aspect Ratio (PAR) dictates virtually all digital formats, both HD and SD. DVCProHD, Digibeta, HDCAM SR, D5 are all formas that do not natively make up a 720 or 1080 format. All digital images use some form of anamorphic stretch. To criticize HDV for this is kind of silly..
What has long been a bone of contention with me, and one I have written about previously, is that Real technical knowledge is far too often supplanted by Application specific skills. That we replaced the video engineer with the software user and traded away Real Core Knowledge of production technologies for the pseudo-knowledge of corporate driven brand loaylty.
It really is time to move beyond this narrow conceptualization of the craft and artistry of production and in particular its certainly time to let go of these absurd prejudices we hold against HDV which just don't stack up. Time to embrace detailed technical knowledge and craft. Its the knowledge of how best to use the format, how to treat, light and process it, that dictates quality and functionality far beyond the format itself.
This
PDF primer from Sony on the HDV format is a good place to start to understand the key elements of the HDV structure; long GOP, anamorphic frame dimensions, bitrates and chroma sampling. Get your head around those and you can go back to focusing on lighting and framing and creative manipulation of technology and forget the diatribe of misinformation.
Posted at 12:00AM Nov 08, 2007
by Mike Jones in video |
