alternatively, you may want to add projectors to a hub on an ethernet network.
refer back to 3.8, adjusting system parameters and advanced controls for complete information about communicating with multiple projectors.
matching colors in multiple screens
in a multiple-projector wall, you will likely want to precisely match color and intensity from image-to-image so that the full wall is as uniform as possible. this matching is typically done in conjunction with brightness uniformity and edge blending.
preliminary calibration
as a final part of the manufacturing process, all primary colors in the projector are precisely set to pre-established values to ensure that overall color performance is optimized and is as accurate as possible (refer back to figure 3.19). upon installation at a site, however, lighting and other environmental factors may slightly change how these colors appear on your screen. while the change is negligible in most cases, you may prefer to recover the originally intended color performance before trying to match colors from several projectors. or you may be renting a projector in which the colors were corrected for use at its previous site, but are not ideal for yours.
the recommended first step in achieving such consistency is to use a color meter to measure the native primary colors—red, green, blue, and white—as they appear at the screen and record these as color primary settings in the service menu (passwordprotected) for each projector. on the basis of these new values, which are stored in memory, each projector will then automatically calculate any necessary corrections to reproduce the original factory colors under the current environmental conditions. this essentially calibrates a projector to its surroundings, compensating for factors such as screen type, lamp and/or ambient lighting that can alter the final color characteristics on-screen, and will improve color accuracy and consistency in a group of projectors. it ensures a good starting point for further customizing and matching.
to return to the factory-set color primaries, such as when a projector is moved to different site, you must access the service menu (password-protected). select the reset to factory defaults? option in the color primaries submenu. then repeat the calibration process describe above, if desired, and continue with matching of colors.
color adjustment procedure
once the color primary settings are calibrated for the site (see above), use the color adjustments by x,y or color saturation menu to further refine each projector’s fundamental colors so that the hue and intensity of each color appears the same from one display to another. once matched, you will have created a single new shared range of colors or “color gamut” that all of your projectors can produce. this palette—named user 1, 2, 3 or 4—can be applied or disabled for a source at any time throughout a bank of adjacent displays, simplifying both the setup and maintenance of a “seamless” wall.
1. set up and optimize all projector settings. you can ignore color temperature, since you will be redefining color performance in this procedure, but do optimize each projector in every other aspect. closely align all screen edges.
2. assign projector numbers to make communications easier. use a wired keypad.
3. use the same lamp mode for all projectors, and do the following:
1)set select color adjustment to “max drives”
2)display a full white test pattern
3)adjust lamp power and optical aperture until adjacent white fields appear the same brightness.
4. display the color adjustments by x,y menus for all projectors. each menu shows the x/y coordinates defining the “max drives” color gamut for this projector. jot down the values shown in one (any) of the displays. see figure 3.31. or use the “copy from” function to copy them into a “user” gamut in one projector.
5. in each projector, select a “user” color adjustment (1-4) to enable color adjustments by x,y changes. then enter your recorded x/y values into each menu (figure 3.32).
6. in each projector, judge by eye and adjust x/y coordinates slightly in the following manner:
1)to match reds, decrease “red x” until full field red screens match.
2)to match greens, decrease “green y” until full field green screens match.
3)to match blues, increase both “blue x” and “blue y” until full field blue screens match.
for speed, enable the “auto color enable” checkbox. each color coordinate you select will then automatically trigger a full field display of the corresponding color.
these coordinate adjustments move the three color points closer together (refer back to the chromaticity chart shown in figure 3.19) to establish a “shared” gamut attainable by all projectors in your group. adjust only as necessary to ensure that the resulting color palette is as large as possible. when done, you may need to adjust lamp power slightly.
7. all screens should now be color-matched. apply this new “user” gamut to a source at any time by selecting it in the “select color adjustment” list accessed in the advanced image settings menu.
using the color saturation menu for color matching
you may prefer to use the color saturation menu to match colors across multiple screens.
in the three color adjustment submenus (red, green, blue—see right), set all main values to 100 and the secondary values to 0. then judge by eye and adjust the slidebars as needed. note that adjustments here define new x/y coordinates in the color adjustments by x,y menu.
achieving brightness uniformity
what is brightness uniformity? when used to refine screens already matched for their primary colors (see matching colors in multiple screens, above) and overall light output, proper adjustment of brightness uniformity can create an exceptionally smooth screen in which:
no area of the screen appears more red, green or blue than another
no area of the screen appears brighter than another
color and light output from one screen closely matches adjacent screens
although the brightness uniformity control can be used for a stand-alone projector, it is particularly useful for setting up and maintaining tiled images that form a cohesive display wall in which the color “cast” and light output appear uniform throughout each image as well as throughout the entire wall. the procedure provided here assumes a multiple-screen application.
before you begin
read through the entire procedure before attempting to adjust brightness uniformity controls, and keep in mind the following checklist of prerequisites and guidelines:
1 adjust colors first—always adjust the primary colors as described in the “matching colors in multiple screens” procedure (above) before attempting to work with brightness uniformity. this ensures that primary colors, color temperature, and maximized light output are all well-matched from one screen to another. these matches are needed before you can achieve good brightness uniformity results.
2 run lamp for 100 hours—light output and brightness uniformity can vary significantly during the first 100 hours of lamp use. for best results with new lamps, either set up brightness uniformity after this period, or do an initial setup and re-check at 100 hours.
3 set lamp power—make sure each “lamp power” setting is as high as possible for your application while still maintaining a good overall match of light output from screen-to-screen. by nature, achieving a uniform brightness will require a slightly reduced overall brightness—this reduction will help ensure that you have enough range of adjustment when examining brightness variables more closely from screen-to-screen, and will help prevent premature “maxing out” when trying to match to a certain color, zone or projector.
4 use a “user” color temperature—always adjust brightness uniformity for a user color temperature defined when you matched primary colors, and continue to use it for all sources displayed on the wall. your other color temperatures will not necessarily be matched from screen-to-screen.
5 white uniformity slidebars—white uniformity slidebar values may not reduce to “0”. each slidebar adjusts overall light output in a specific screen zone, but the value shown represents the current setting for green in this zone. when other “hidden” values (red or blue) are lower than green, during adjustment in the white uniformity menu their values will reach “0” first, causing the slidebar to stop earlier than expected.
6 judge by eye or use a meter—good brightness uniformity can be achieved with either.
step 1: general setup
1a) adjust primary colors (see matching colors in multiple screens) to ensure matched overall color temperatures and light output between screens.
double-check that all whites and light output are well-matched.
1b) enable the brightness uniformity checkbox. this will enable access to the uniformity controls and will apply the settings to your image.
1c) select the 13 point test pattern for display. this pattern provides 9 screen “zones” with 13 targets.
for best results: rather than examining the center of each zone when assessing brightness uniformity adjustments, focus on extreme edges as indicated in the illustration at right.
1d) in either color adjustments menu, select a “user” color. then:
if you have created a “user 1” color gamut (recommended) for a wellmatched wall, continue to step 1e.
if you prefer maximum brightness rather than a particular color temperature, select “max drives”.
do not change user 1 color adjustment in color-matched applications!
1e) in the white uniformity menu, set the “overall” output level to 50.0 and all remaining slidebars to 0.0. this decreases the light output just enough throughout the screen so that any color level can then be increased later as necessary for matching light output from zone-to-zone. do not exceed 50.0 for “overall”—a higher level will likely interfere with achieving brightness uniformity and is not recommended.
ensure that overall light output remains well-matched from one screen center to the next. where necessary, increase or decrease lamp power slightly to recover center matches.
step 2: adjust color (level of red/green/blue) in 8 zones
1) at this point, ignore the brightness of individual zones. 2) always ignore menu colors.
2a) on each screen, compare the color temperatures in the 8 target zones (4 edges and 4 corners) to that of the color temperature of the center. compare using a white field only, and take note of any areas that do not match the center. also decide if any screen exhibits a more obvious color shift than other screens—begin with this screen in step 2b.
2b) return to the brightness uniformity menu. beginning with the screen that exhibits the most obvious color shift(s), for each edge that exhibits a noticeably different color temperature from the center, select the corresponding uniformity adjustment menu—left, right, top or bottom. for example, if any part of the left side is too blue, too red or too green, go to the left uniformity menu and adjust the colors (i.e., change their light output) until all portions of the left side closely match the center color temperature. adjust an edge first (focusing on its center), then adjust its corners. see figure 3.34.
repeat the color adjustment of sides and corners for each edge of the screen that does not yet match the center (note that each corner is adjustable in either of its two adjacent “side” menus). when done, all areas of a given screen should match. repeat steps 2a & 2b for all remaining screens.
step 3: adjust light output in 8 zones
3a) for each screen, compare the light output of each edge and corner to that of the center. if any of the areas differ, use the white uniformity menu to match edges and corners to the center as described below (see figure 3.35). begin with the screen exhibiting the most obvious variations in light output.
adjust edge white uniformity first—note that each edge adjustment also affects the rest of the screen slightly. keep all edges just slightly lower than the center light output rather than matching light output precisely. otherwise, it may not be possible to brighten the corners (typically the dimmest areas of the screen) enough. i.e., the best uniformity is a compromise between the brightest and darkest areas of the screen.
adjust corner white uniformity last—each corner adjustment affects only this quadrant.
repeat for each screen.
step 4: readjust color temperature (level of red/green/blue) in 8 zones
4a) return to steps 2a & 2b and, if necessary, fine tune the zones so that they all still exhibit a single color temperature.
canceling brightness uniformity
if you do not want to use or apply brightness uniformity settings, delete the checkmark from the “uniformity enable” checkbox at the top of the brightness uniformity menu.
edge blending
christie edge blending is an innovative set of software functions that can quickly and easily blend whitelevels along the edges of multiple adjacent projected images to create a single seamless larger image.
what is a blend?
in simple terms, a blend appears as a gradient strip along an edge of a projected image. it is darkest along the extreme edge of the image, and lightens nearer to the rest of the image (see right).
how are blends used?
in multiple-projector walls, complementary blends between neighboring images can compensate for the extra “brightness” or intensity where these edges overlap. by controlling blend width and other properties, you can achieve uniformity across the group of images. visible overlaps will disappear:
for best results, use the same projector model and type throughout your display wall. in addition, avoid high-gain screens whenever possible—the optical performance of such screens demands minimal image offset, thus projectors must be located very close to one another.
edge blending software controls are located in the 2-page edge blending submenu—access via configuration menu, then go to the geometry and color menu and select edge blending. the more option opens the second page of the edge blending submenu.
main functions
use edge blending controls to set the precise width, shape and midpoint you need to blend overlapping edges together smoothly.
1 blend width determines how much area is used for blending along an overlapping edge. slidebar values represent the number of 8-pixel steps used for the blend. for example, a setting of “3” creates a blended edge 24 pixels wide. a setting of “0” signifies no blending. for best results in most applications, use a blend width of 16-48 steps (128-384 pixels).
ranges: 0-80 horizontal, 0-60 vertical.
2 blend shape determines the rate of roll-off across the blend width, i.e. how quickly the white levels across the blend change from light and dark. increasing the blend shape setting accelerates the rate of change at both extremes so that less of the region appears mid-gray (see figure 3. 37). decreasing the blend shape setting slows the rate of change so that more of the region appears mid-gray. for most applications, this subtle control is best left close to 50.
3 blend midpoint determines the white level at the blend midpoint (the point equidistant between the beginning and end of the blend). increasing the blend midpoint setting creates a blend that appears brighter than the rest of the image. decreasing the blend midpoint setting creates a blend that is darker than the rest of the image. a setting of 50 means the midpoint is approximately 50% black—for best results in most applications, keep fairly close to this default.
other functions
for convenience, the edge blending submenu also includes related options for enabling a specific color and/or test pattern, or for working with colors or the lamp. such functions duplicate those provided elsewhere in the menu system.
edge blending procedure
before attempting to work with edge blending software functions, you must 1) physically align the projectors/images by correctly overlapping the displays from your intended external source, and 2) match colors and brightness uniformity.
for a shared edge, all blend procedures and settings should be identical on both projectors.
1. start with 2 projectors. display full white field test pattern from both.
2. in the edge blending submenu, enable edge blending by entering a checkmark in the top checkbox.
3. set starting points for adjustment:
1)set all blend widths to 0.
2)go to “more” and set everything in the edge blending (2) menu to 50.
4. set blend width: on one projector, increase the blend width for an overlapping edge (for example, if the projector’s image is on left, its right edge overlaps the adjacent image—adjust right blend width). use the same setting on the second projector for this shared edge.
5. re-adjust width (both projectors) until the overly bright band at the midpoint of the overlapping blends disappears or just changes to very light gray. for the shared edge, use the same blend width setting on each projector. if the “best blend” appears to be between two settings, choose the wider setting for both projectors.
6. check blend: if the blended region appears too dark or light in relation to the rest of the image:
1)increase blend midpoint in both projectors to “lighten” the overall blend, decrease to “darken” the overall blend.
2)adjust blend shape in both projectors to fine-tune change the amount of mid-gray intensity (as opposed to black/white) in the blend.
7. repeat with remaining projectors / overlaps.
8. check completed display wall with the desired external signal.
9. adjust mechanical alignment if necessary to maintain perfect pixel-on-pixel alignment over time.
in applications where you are projecting only white or light images, the blend width may be slightly higher—set according to how much overlap you have between images. use the following as a guide (examples show overlapping width only—values for overlapping height will differ):
1 if side overlap is 15%, set blend width to 24
2 if side overlap is 20%, set blend width to 32
3 if side overlap is 25%, set blend width to 40
4 if side overlap is 30%, set blend width to 48