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Lexmark Optra C710 User's Guide - Page 96

Halftone screens, Attributes, Screen frequency

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Halftone screens The term halftone screen, refers to the pattern of dots applied to an image. If you look closely at a black and white photograph in a magazine, it appears to contain many shades of gray. If you place the same picture under a magnifying glass, you see that it is actually composed of a number of dots. These dots, also known as pels, may be of varying sizes or varying tones. They may also be the same sized dots applied to a tint of color. Without halftoning, it would not be possible to produce quality photographic images on a page printer. This process of representing an image as a series of halftones, is known as halftone screening. Note: When printing color, you cannot change the screen angle settings. The reason for this is the angles have been set to prevent one color from over printing another color. You can control the attributes for halftone screens by changing the values to your halftone screen frequency and screen angle settings. You can change these settings through the graphics tab on your printer driver. Frequency (cells per inch) Attributes Spot function Angle Halftone screens have three main attributes. They are: screen frequency, screen angle, and spot function. The halftone screen is further divided into halftone cells. These cells contain the individual pel spaces. The screen frequency and angle attributes determine both the number of halftone cells that make up a halftone screen and the orientation of the cell. The spot function determines which of the individual pels in the halftone cell is turned on to represent a particular gray level or color tone. The illustration shows a halftone screen and halftone cells rotated 45 degrees. Screen frequency The screen frequency is the number of halftone cells per inch. A larger number in the screen frequency increases the number of halftone cells per inch. Increasing the number of halftone cells per inch will not necessarily give you better quality. The reason for this is the higher settings may make the colors or halftones seem to run together or bleed. 82 Chapter 4: Using color

Section	Page
Table of contents	3
Using your documentation ix	3
Trademarks xiii	3
1 Introducing your printer 1	3
2 Using printer drivers 5	3
3 Changing printer settings 7	3
4 Using color 75	4
5 Managing memory 89	5
6 Handling paper 95	5
7 Replacing supplies 113	6
8 Solving printer problems 145	6
Appendix A: MarkVision 189	7
Appendix B: Printer specifications 201	7
Appendix C: Fonts 205	7
Appendix D: Safety information 215	7
Appendix E: Notices 227	7
Appendix F: Warranty 239	8
Glossary 241	8
Index 255	8
Using your documentation	9
About the manuals	9
Other sources ofinformation	11
Trademarks	13
Introducing your printer	15
Print speed	16
Memory	16
Color quality	16
Printer drivers	17
MarkVision	17
Paper handling	17
Using printer drivers	19
Changing printer settings	21
Using the operator panel	22
Menus	24
Using color	89
Understanding color	89
Managing color	92
Controlling your printer	94
Color Correction	98
Avoiding print quality problems	100
Managing memory	103
Printer memory	103
Adding memory	104
Flash memory	106
Hard disk	106
Managing resources downloaded to flash or disk	107
Handling paper	109
Paper sources and output bins	109
Paper sizes	110
Media guidelines	112
Storing media	118
Avoiding paperjams	118
Loading paper inthe trays	119
Tray linking	123
Using the multipurpose feeder	124
Replacing supplies	127
Ordering supplies	127
Storing supplies	129
When to replacesupplies	130
Recycling usedsupplies	133
Conserving supplies	133
Replacing supplyitems	134
Replacing print cartridges	135
Replacing the coating roll	140
Replacing the fuser kit	145
Replacing the transfer kit	152
Solving printer problems	159
Printer problems	159
Theory of operation	160
Understanding printer messages	161
Identifying other problems	175
Clearing printer paperjams	182
Clearing duplex unit paperjams	189
Cleaning the print cartridge dust collector	195
Cleaning the waste toner sensor	198
Calling for customer support	202
MarkVision	203
Operating systems supported	203
Introducing MarkVision	204
Installing MarkVision on a network	212
Getting updated utilities and drivers	213
Printer specifications	215
Fonts	219
Printing font samples	219
Resident fonts	220
Symbol Sets	225
Downloadable fonts	227
Safety information	229
Notices	241
Laser notices	245
Warranty	253
Glossary	255
A	255
B	256
C	256
D	257
E	258
F	259
G	259
H	260
I	260
J	260
K	260
L	261
M	261
N	262
O	262
P	263
R	265
S	265
T	267
U	267
V	267
Y	268

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Chapter 4: Using color

Halftone screens

The term halftone screen, refers to the pattern of dots applied to

an image. If you look closely at a black and white photograph in

a magazine, it appears to contain many shades of gray. If you

place the same picture under a magnifying glass, you see that it

is actually composed of a number of dots. These dots, also

known as pels, may be of varying sizes or varying tones. They

may also be the same sized dots applied to a tint of color. With-

out halftoning, it would not be possible to produce quality pho-

tographic images on a page printer. This process of representing

an image as a series of halftones, is known as halftone screen-

ing.

Note:

When printing color, you

cannot change the screen angle

settings. The reason for this is the

angles have been set to prevent

one color from over printing

another color.

You can control the attributes for halftone screens by changing

the values to your halftone screen frequency and screen angle

settings. You can change these settings through the graphics tab

on your printer driver.

Attributes

Halftone screens have three main attributes. They are: screen

frequency, screen angle, and spot function. The halftone screen

is further divided into halftone cells. These cells contain the

individual pel spaces. The screen frequency and angle attributes

determine both the number of halftone cells that make up a half-

tone screen and the orientation of the cell.

The spot function determines which of the individual pels in the

halftone cell is turned on to represent a particular gray level or

color tone. The illustration shows a halftone screen and halftone

cells rotated 45 degrees.

Screen frequency

The screen frequency is the number of halftone cells per inch. A

larger number in the screen frequency increases the number of

halftone cells per inch. Increasing the number of halftone cells

per inch will not necessarily give you better quality. The reason

for this is the higher settings may make the colors or halftones

seem to run together or bleed.

Frequency

(cells per inch)

Angle

Spot function