All posts by Igor Ridanovic

Unnatural Proportions on 16×9 Screen

Those people aren’t fat, just stretched

Just about every bar in the country is now equipped with at least one 16×9 size flat screen TV. The problem is that most of the programming is still produced and broadcast in 4×3 aspect ratio.

There are two options for displaying all familiar 4×3 SD video in a 16×9 widescreen monitor. You can center the smaller 4×3 image and leave the sides of the monitor unused. Alternately you can stretch the video horizontally to fill up the entire screen.

Unfortunately, most people select the stretch option which has an unpleasant side effect of making everyone look wide faced. Properly set TV as illustrated in Figure 1 comes at a price. A plasma screen and even LCD screens may develop a permanent “burn” due to underutilization of the black pillarboxed area. Better TVs have screen savers that minimize the damage by shifting the picture by minute amounts. While a screen saver like this can save a home HDTV it is generally unacceptable to use such devices in professional environment where steady image is required.

stretched TV image

Fig 1. wrong proportions on widescreen TV

Equipment, Post Production, Technical Info

Flicker on HD Monitors

The name of the game in 23.98p.

Your video monitor is not broken. At 1080 23.98p the screen will exhibit a flicker artifact more visible in bright scenes. It is a product of a relatively slow frame rate. Flicker sensation is more enhanced if you place the TV in your peripheral vision. While unpleasant this artifact is easy to get used to.

720 59.94p will not show any flicker even when shot in Varicam in 23.98p mode. The reason is that the actual frame rate of the format is roughly 60 pictures a second which is high enough to trick the brain into not seeing flicker.

The viewers at home are not likely to see the flicker because HD in the U.S. is broadcast as either 1080 59.94i or 720 59.94p.

Equipment

Plasma Monitors

Similar to CRT but flat.

Plasma screens are most often compared to LCD monitors due to slim external appearance but the principle of operation is actually similar to the inner workings of a CRT screen.

Plasmas are fairly color accurate although rarely used for professional applications due to unavailability of professional grade monitors and high cost. They cost substantially more than LCD monitors. Plasmas can be manufactured at sizes larger than LCDs which makes them appropriate for use in public information displays.

Plasma monitors fade over time much like CRTs and can be burned-in by an unchanging image. Some models exhibit video processing delay which will disturb sync between sound and picture. Low air pressure at high altitudes may affect performance of the display.

Equipment, Post Production

NLE. What is It?

It’s your editing computer.

NLE stands for Non Linear Editor. Tape based edit systems were “linear.” The videotape medium necessitated editing in chronological order.

NLE’s allows editors to jump back and forth, hence the non linear designation.

Equipment, Production

Lenses for HD

Use the best glass available.

Although many lenses designed for standard definition ENG will fit HD cameras it is generally better to use lenses specifically designed for HD.

Lens design and manufacture is a delicate dance between cost, functionality and quality. Unlimited R&D resources could produce the world’s best lens. Maybe such lens would even be functional and practical enough for actual use but it would undoubtedly cost more than what the market can bear. In reality lens are designed to control cost of manufacture and this introduces imperfections.

Standard definition TV lenses have their share of imperfections. On a better quality SD lens those imperfections may not be visible. Once the lens is mounted on an HD camera chromatic aberration and other anomalies that were invisible in SD can suddenly become objectionable.

HD lens are designed and manufactured using higher standards than their SD counterparts. Your camera will record only what it sees. Don’t deprive it of the best glass available.

Equipment

LCoS Monitors and Projectors

A Promissing projector technology.

LCoS (Liquid Crystal on Silicon) uses a similar approach to DLP technology. Instead of using miniature mirrors like DLP, LCoS devices use liquid crystal coated over a specially prepared highly reflective surface.

A light beam bounces off the LCoS chip (or chips in three-chip design) and is focused through the lens.

LCoS is relatively inexpensive to produce and offers very high quality images.

Equipment

LCD Monitors

Getting cheaper by the minute.

It is important to consider advantages and disadvantages of LCD (Liquid Crystal Display) monitors before committing to purchase one. Although the technology has improved and prices have come down in the last several years LCD monitors are still not the best choice for the most critical color work.

However, the technology has many advantages to its credit. Price points for LCDs versus traditional CRT are lower. The monitors are lightweight, very bright, have a small footprint, consume less power and can offer picture of outstanding sharpness. LCDs are more consistent so calibration and color profiling does not need to be as frequent as in case of CRTs.

LCDs are a good choice for on the set use due to high brightness and low weight but they can be sensitive to strong heat if left in the sun for prolonged periods of time.

LED backlight LCD monitors are a recent development. This technology is capable of delivering dynamic range (range from minimum black to maximum white) comparable to that of traditional CRT monitors.

On the negative side, most other LCD monitors lack the ability to produce dynamic range necessary for color critical use such as color correction. Black is typically never as dark as black on CRT monitors. Viewing angle of LCD monitors is limited which means that more you step to the side less accurate the color reproduction is. This problem is so acute on some monitors that it is virtually impossible for two people to see identical color even if they put their heads cheek to cheek. LCD screens can have problems displaying interlaced video which limits the usability in an edit bay. Almost all LCDs delay video which puts sound and picture out of sync.

Equipment, Production

Is HDV Good Enough for Broadcast?

Yes unless your network says otherwise.

You can think of HDV as an HD equivalent of MiniDV. It’s probably fair to say that HDV to HDCAM tape format is what MiniDV is to Digital Betacam.

It is a cheap, consumer tape format that gets the job done. HDV camcorders lack robust features found on higher end cameras but are adequate for many jobs where DV formats would normally be used in SD.

At this time 1080 59.94i and 720 59.94p recording formats are available in North America. An important thing to remember is that HDV uses 25Mbps bitrate and 19Mbps bitrate in case of 720p. This bitrate is the same or lower than the bitrate of DV in SD while the image size is much larger. HDV uses a lot of data compression.

Any material that will be extensively color corrected or used in compositing may not hold up well because of high compression and 4:2:0 color sampling. The best thing is to test before committing to the format.

Post production can be a bit more complicated with HDV format although some editing systems do a decent job of automating certain tasks under the hood and away from your eyes. HDV uses long GOP structure which does not allow editing on every frame.

Overall HDV will deliver but you can’t ask for too much. Check with your executive because most networks limit how much HDV originated material can be used per show.

Equipment

HDV Format

Consumer acquisition format.

HDV is an inexpensive high definition format intended for consumer and “prosumer” use. It utilizes MiniDV tapes and the same 25Mbps bandwidth as standard definition MiniDV recording. The signal is heavily compressed using MPEG2, the same codec used for DVD. This creates less than perfect situation for NLEs. The long GOP structure does not allow for editing on any frame and material must be transcoded to a different codec or to uncompressed storage prior to editing.

Several manufacturers support HDV format.

HDV works in 1080i and 720p standards. The actual available standards depend on the camera model. Although the format clearly lags behind in quality, the first generation recording in HDV can be quite good looking. Color correction and compositing operations tend to quickly degrade the quality of HDV footage.

Most networks limit the percentage of HDV originated material per show. Check with your executive before committing to shoot using HDV.

Equipment

HDCAM SR Format

Sony high end acquisition and mastering format.

HDCAM SR is Sony’s state of the art CineAlta high definition format. It is an extension of HDCAM format. HDCAM SR is intended for high end color critical work and general D-cinema acquisition using 4:4:4 sampling structure.

Robust studio VTRs allow mastering in HDCAM SR format.

HDCAM SR works in 1080 and 720 size in either interlaced or progressive mode. It provides the following frame rates: 23.98p, 24p, 25p, 30p as well as interlaced frame rates: 50i and 59.94i.

The format uses selectable 4:4:4 or 4:2:2 sampling and records mildly compressed (2.7:1 – 4.2:1) 10 bit signal to tape at 440Mb/second.