Barco GRAPHICS 500 R9002930 User Manual
Size:
6.88 Mb
Download

7. Image Menu

Image 7-23

7.7Blanking

Blanking in the Image menu

The blanking in general allows to blank unwanted video information (noise in the top or bottom of the image).

The blanking in the image menu is the same as in the Display settings menu except for the fact that here the blanking settings are stored in the image files. In other words each custom file or source has its own blanking values.

See the blanking procedure in the Display settings menu.

If the selected source is not entirely displayed always check first the blanking settings in the image menu since the active custom file may contains blanking.

7.8Input balance

Introduction: Unbalanced color signals

When transporting signals, there is always a risk of deterioration of the information contained in the signals.

In case of information contained in the amplitude of the signals which is the case of data color signals (R, G, B),image 7-24 ,weare quite sure that the amplitude of these color signals is subject to alterations.

An example of alteration may be a DC component added to the signal, in the form of a DC offset repositioning the black level, since this black level (“brightness”) will become crucial later on ( clamping circuit) it will result in “black not being black”.

Another value that is subject to alteration is the amplitude of the signal, resulting in an altered “Gain” of the signal (“white level” orcontrast ).

The alterations of the three color signals will happen independently i.e. the colors will end to be unbalanced, image 7-25

B

0.7V

Black level

Image 7-24

R5976367 BARCOIQ GRAPHICS 500 01/02/2007

 

69

7. Image Menu

G B

R

R

G

∆Β

 

 

Black level

Image 7-25

One can conclude here that a good color tracking can only be met by using three previously (input) balanced color signals

Analog Digital Conversion

The analog color signals must pass through an Analog/Digital conversion circuit prior to any digital processing in the PMP. A typical ADC transforms the analog value into an 8 bit coded digital signal.

The graphic shows that when converting a signal containing a DC offset component the range of the converter is not optimally used.

ADC

R

 

255

 

 

 

 

 

 

 

i2 : video information

 

0

i1 : superfluous information

 

Black level

 

 

 

 

 

Image 7-26

 

 

 

One can conclude here that a good data conversion can only be met by using three previously (input) balanced color signals

The objective of input balancing

The objective in input balancing is to “set” the same black level and the same white level for the three colors of a particular input source.

Black level setting : brightness

White level setting : contrast

The same absolute black and white level for the three colors allows the same reference for Brightness and contrast control of the picture !

These two references also set the range in which the ADC will work for that particular source ( this explains also why each input balance setting is linked to a particular source and thus saved in the image file).

How can it be done ?

To balance the three color signals of a particular source there are conditions; in fact we must know the black and the white level of the source i.e. :

1.the source in question must be able to generate a white signal, ideally a 100% white (background) full screen pattern

2.the source in question must be able to generate a black signal, ideally a 100 % black (background) full screen pattern

70

 

R5976367 BARCOIQ GRAPHICS 500 01/02/2007

7. Image Menu

A B

Image 7-27

White balance : In the projector, we will set the contrast for each color until we get a 100% light output picture when projecting a 100% white image (image A)

Black balance : In the projector, we will set the brightness for each color until we get a 0% light output picture when projecting a 100% black image (image B).

The changeover from min to max is indicated by the apparition of bright spots also called “digital noise”

An alternative to a full screen White/black pattern is the standard gray scale pattern, the white bar will be used for white balance and the black bar for black balance.

Image 7-28

Black balance

1.Press MENU to activate the Toolbar

2.Press → to select the Image item

3.Press ↓ to Pull down the Image menu

4.Use ↑ or ↓ to select Input balance

5.Press → to pull down the menu

6.Use ↓ or ↑ to select Black balance (image 7-29)

7.adjust the red black level on a minimal value (image 7-30, image 7-31)

8.adjust the blue black level on a minimal value

Note: this minimal value is not necessary , provided that the 2 other colors are not influencing too much the color to be adjusted, in fact the aim is to minimize the effect of the two other colors since there is a risk of reaching too soon the 50% transition due to the contribution of these two other colors signals.

9.Adjust the green black level until bright spots appear on the screen

10.adjust the blue black level on a minimal value

Note: this minimal value is not necessary , provided that the 2 other colors are not influencing too much the color to be adjusted, in fact the aim is to minimize the effect of the two other colors since there is a risk of reaching too soon the 50% transition due to the contribution of these two other colors signals.

11.Adjust the green black level until bright spots appear on the screen

12.Adjust the Blue black level until bright spots appear on the screen

13.Adjust the red black level until bright spots appear on the screen

the projected image should know be noisy full black

R5976367 BARCOIQ GRAPHICS 500 01/02/2007

 

71

 

7. Image Menu

Image 7-29

Image 7-30

Image 7-31

Performing White input balance

1.Connect the source you want to project

2.Select a white pattern (or gray scale as alternative)

3.Press MENU to activate the Toolbar

4.Press → to select the Image item

5.Press ↓ to Pull down the Image menu

6.Use ↑ or ↓ to select Input balance

7.Press → to pull down the menu

8.Use ↓ or ↑ to select White balance (image 7-32)

9.adjust the red white level (gain) on a minimal value (image 7-33)

10.adjust the blue white level (gain) on a minimal value

Note: this minimal value is not necessary , provided that the 2 other colors are not influencing too much the color to be adjusted, in fact the aim is to minimize the effect of the two other colors since there is a risk of reaching too soon the transition (bright spots) due to the contribution of these two other colors signals.

11.Adjust the Green white level (gain) until bright spots appear on the screen

12.Adjust the Blue white level (gain) until bright spots appear on the screen

13.Adjust the Red white level (gain) until bright spots appear on the screen

the projected image should know be noisy neutral grey.

72

 

R5976367 BARCOIQ GRAPHICS 500 01/02/2007

 

7. Image Menu

Image 7-32

Image 7-33

if one uses a gray scale pattern, the bright spots should appear in the white bar.

Selecting Preset restores the factory input balance setting

Remark on the input balance of a component video source

Before starting the Input Balance procedure, generate a signal with dominant white parts.

Input balance is also available for a component video source under following conditions:

A component video signal is present on the BNC’s

”Data on BNC’s” is selected in the Source selection menu

Cr/Y/Cb is selected in the Advanced menu of the corresponding image file

The procedure is the same as for a data source except:

R5976367 BARCOIQ GRAPHICS 500 01/02/2007

 

73