DGA-6000 ULTRA-HD VIDEO GENERATOR / ANALYZER USER MANUAL
B-11
individual observer. Individuals may prefer to use different versions of the resolution wedges (2, 6,
or 14 cycle). This illustrates why the Kell factor is subjective and no single value applies to all
displays or all observers.
5) To measure the effective vertical resolution with movement, set the vertical movement increment
(Vxx) to a non-zero value, and reposition the cursor to the highest discernable spatial frequency on
the moving Vertical Resolution Wedge. The discernable vertical resolution will typically decrease as
the vertical rate of movement is increased.
6) To measure the vertical resolution at the horizontal edges of the display, momentarily enable
horizontal movement to position the resolution wedge at the side of the screen. You can also select
a wedge pointing in the opposite direction to make measurements easier at the opposite side of the
display.
Expressing effective resolution as a % of Nyquist is very convenient since it is independent of the
display’s nominal resolution and video signal format. However, you can also express resolution as
Lines/PW or Lines/PH (TVL). Select the desired measurement unit from the Units menu item.
Linear Horizontal and Vertical Frequency Sweeps –
Linear horizontal and vertical spatial frequency
sweeps are provided at several sweep rates in rectangular windows and full fields. Spatial frequency
response, and therefore resolution, may be limited by anti-aliasing filtering during any kind of motion
processing, or during scaling (or overscan) of static images. The active cursors can be used to visually
determine the effective frequency response versus motion rates.
Detail Discs –
Detail discs provide an easy way to evaluate and compare the ability of displays to
differentiate fine detail versus motion rate and direction. Detail Discs are provided with horizontal slices,
vertical slices, squares, and checker patterns with 1 pixel, 2 pixel, 4 pixel, and 8 pixel sizes. The horizontal
slice detail discs are also particularly good at revealing line twitter with vertical motion, and for assessing the
performance of deinterlacing processing for interlaced video formats using video or film cadences.
Cosine Balls –
Cosine Balls are provided in a variety of sizes appropriate for standard-definition and high-
definition signal formats. The smoothly varying surface brightness of the Cosine Ball will reveal objectionable
non-linear video processing artifacts such as motion-induced contouring (MIC), which manifests as
contouring rings on the ball surface only during motion. The contrast within contouring rings typically
increases at higher motion rates. (The number in the Ball name [Ball 256] is the radius in pixels of the ball.)
Standard-Definition vs. High-Definition Patterns –
All motion patterns are generated by calculating
precise video values on the native pixel grid of each video format (i.e. a 1080p pixel grid is 1920 x1080
pixels, while a 480p pixel grid is 720 x 480 pixels). High-definition formats have “square pixels”, which
means the physical spacing between pixels on the display screen is the same distance horizontally as
vertically. Standard-definition formats however, do not have “square pixels”. The horizontal display spacing
between pixels is physically slightly different than the vertical spacing.
To avoid adding interpolation or scaling artifacts to the test patterns, which would then mask or interfere with
identifying and measuring the display’s performance and video processing artifacts, no scaling or
interpolation of any kind is performed by the DGA-6000. For instance, the square details in the detail disc
patterns are precisely 1, 2, 4, or 8 black or white pixels in length vertically and horizontally, so they are
physically slightly rectangular rather than square on screen for standard-definition video formats. In order to
preserve physical “squareness” the generator would have to interpolate intermediate gray pixel values,
rather than black and white pixel values on a standard-definition pixel grid. If that were done, the resulting
“fuzzy” pattern would degrade the ability to discern detail.
Zone plate patterns are treated the same way to eliminate interpolation and scaling artifacts. Precise
electronically generated circles (using the standard circular formula x^2 + y^2 = radius^2 for instance)
appear as physical circles for high-definition formats. However, because the standard-definition formats
(480i/p, 576i/p) do not have square pixels, digitally generated “circles” appear slightly elliptical when
displayed without scaling or interpolation. However, that ensures all patterns are ideally generated with
perfectly uniform spatial frequency response and free of artifacts for the evaluation of displays and video
processors.
