Runco REFLECTION CL-510 Bedienungsanleitung PDF herunterladen (Seite 14)

TECHNICALLY SPEAKING...

14 ExtroNews 14.3 Fall 2003

Since, in an RGB output from a graphics system,

the white reference bar contains equal amounts of

red, green, and blue, full voltage excursion should

be seen on each color channel when using a

scope

ee Figure 3

)

. In addition, any primary

color should be 100% level where it contributes

to any color recreation.

NTSC/PAL Television Group

The following patterns are designed for

television performance testing and are enabled

only when “video” is selected.

SMPTE Color Bars

With full conformance to SMPTE 170M and

when generated using a fully digital encoder, the

75% SMPTE color bars standardize adjustment of

color gain, phase, and display black level controls

(ref: SMPTE EG 1-1990). SMPTE 170M speciﬁcally

deﬁnes the composite analog video color signal for

professional studio applications. The light gray

reference bar is followed by the primary and

secondary colors in order of decreasing luminosity.

The SMPTE version modiﬁed previous EIA bars in

two ways. The small color boxes were added in

between the color patches to provide easier, more

accurate adjustment of color level and color phase.

The “PLUGE” stripes were added in the black region

on the lower right to facilitate black level setup.

With only the blue bars viewable (either by

turning OFF the red and green outputs or viewing

through a blue ﬁlter), the color level control is

adjusted until the two outside blue bars match the

intensity of the outside small blue patches. There

should be minimal difference in intensity between

them at the proper setting. Next, the color phase

(tint) control is adjusted until the two inside bars

closely match the intensity of the patch below each.

Some alternating adjustment between color level

and phase is normal since the effect is interactive.

For correct black levels, adjust the brightness

(black level) control so that the black area of the

pattern just matches the “blacker-than-black”

stripe in the PLUGE area. The brighter-than-black

stripe should just be visible.

Viewing the color bar pattern on a waveform

monitor or oscilloscope yields the waveform seen

in Figure 4. Figure 5 shows the correct decoding

on a vectorscope of the color bar signal in the

display system. Note, in the vectorscope photo,

that the phase is very stable and the peak

excursions each fall within the +/-2% box, an

indication of a broadcast-quality generated signal.

EBU Color Bars

EBU color bars are designed for setup and

testing of PAL television signals and displays. The

test pattern lacks the patches for color level setup;

however, due to the construction of the PAL

system, the tint control is not required. Refer to

Figure 6 for a scope or waveform monitor

presentation and Figure 7 to see the vectorscope

presentation. The alternating sets of vector signals

are decoded by the display to mostly cancel

variations in color phase errors. This is why PAL

displays do not have a phase, or tint, control.

Multiburst Pattern

The multiburst pattern may be used for NTSC

and PAL systems. It provides a quick, visual test

of the television display, or system, frequency

bandwidth. Looking at the waveform monitor

presentation of

Figure 8

, we can see that a series

of equal-amplitude sine wave bursts of 0.5, 1.5,

2.0, 3.0, 3.58, and 4.2 MHz respectively (for NTSC)

are imposed on a 40 IRE level. Note that the

signal extends to only 70 IRE. This is designed

to avoid intermodulation effects in NTSC

transmitters; although for laboratory use, 100 IRE

signal amplitude may be used. When system

bandwidth is such that any one or more of the

frequency bursts is attenuated signiﬁcantly, the

brightness of the burst’s transitions tend to dim

toward middle gray. This attribute makes visual

assessment of the system’s performance quite easy.

For PAL, the frequency components around the

subcarrier frequency and band limit are changed

to match the required values of that standard.

Television decoders notoriously attenuate the

upper frequencies around, and including, the 3.58

subcarrier. Color burst is included with this pattern

so as to ensure the chroma processing system is on

and operating. The decoder’s ability to separate

the luminance information (which utilizes the

entire system bandwidth) from the chrominance

information (which is centered about the 3.58

subcarrier frequency) is of paramount importance

for quality imaging of television signals. The visual

integrity of this pattern on a display provides direct

insight into the quality of that process.

Putting the ‘A’ in A/V

A/V techs will ﬁnd that the VTG 300 provides a

suite of audio test signals capable of satisfying

VTG 300 Video and Audio Test Signals — As Good As It Gets (continued)

Red Green Blue

Figure 3: Graphics/PC color bar waveform presentation of individual RGB components.

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