Fred Weiss
Merchant Member
Gerber Edge printing, particularly when using four color process foils, can be a frustrating experience due to the nature of thermal resins as compared to liquid inkjet printing. This is most often noticed with halftone dots causing a grainy appearance as well as banding lines in gradients showing instead of a smooth transition. This is because thermal resins don't blend as readily as liquid inks thus transferring with a "harder edge". In addition, older Edge printers are limited to 300 DPI print quality which is only going to result in "newspaper" quality impressions instead of the "magazine" quality results when printing at higher resolutions.
It is important to note that viewing distance should be taken into account when deciding how important these issues will be in setting up the production parameters. If viewers of the finished sign or graphic will be close enough to touch it, then spending some time adjusting the halftone parameters is more important than if the viewer will normally be further away. For example, a site sign, a banner or a billboard may be at so great a distance that such details are totally unimportant ... while a graphic on a storefront window will be so close that adjustment of halftones will make a great deal of difference in the appearance of the printed image.
There are any number of factors that can affect the appearance of the printed impression which will be left to each user gaining experience in printing with an Edge. This discussion will be limited to two factors that are directly under the designer's control. They are the size and type of the halftone dots that will be printed.
LPI - Lines Per Inch
LPI is what controls the size of each halftone dot that is printed, regardless of DPI resolution capability of the printer being used. The lower the LPI, the larger the dots. The higher the LPI, the smaller the dots. LPI can be manually set with some halftone types and is automatically set with others, usually based on the overall size of the graphic being printed. There are opposing benefits and pitfalls of this setting. The smaller the dot the less grainy and smoother will be the output, but there is also a reduction of tonal quality which can make the print harsher causing banding lines to be seen and some shifting of colors.
If you are manually setting your LPI for any fill or image, the following are the settings I use:
42.4 LPI - Soft results with rare banding but also grainy if viewed up close.
53 LPI - Better appearing results with reduced graininess but with a slight tendency to show banding lines if gradients are present.
70.7 LPI - Excellent appearing results with slight graininess but with a higher tendency to show banding lines if gradients are present. Some loss of tonal quality details.
90 LPI or Higher - Suitable for emulating the appearance of spot colors with little or no graininess. Harsh banding if gradients are present and significant loss of tonal quality. Some color shifting and generally unsuitable for retaining detail in photos and images.
For other insights, search "LPI" in Omega Help.
Halftone Type
Omega provides a choice of halftone types. Some automatically adjust the LPI based on the output size of the print and some allow manual changing of the LPI setting. These choices vary with the type of object being printed. If it is a filled vector, one group is offered and if it is a raster image such as a JPG or a TIF, a different group is offered. The best way to determine which type best suits your needs and preferences is through test printing.
My preference is to manually set the LPI of each object being printed. For filled vectors I most often use Classical Dot. For raster images and photographs I use GerberTone STC Photo.
For other insights, search "Halftone" in Omega Help.
Testing Your Results
As previously mentioned, to see and best understand how these settings and choices will affect the results, I recommend doing a few printouts using manually inputted LPI settings. For filled vectors, create a vertical column of four 2.75" squares. Fill each with the same process color and vary the LPI settings. Also use different colors for each column from bright to dark such as red, green and blue. For raster images, repeat a photo four times and set the LPI differently for each photo.
It is important to note that viewing distance should be taken into account when deciding how important these issues will be in setting up the production parameters. If viewers of the finished sign or graphic will be close enough to touch it, then spending some time adjusting the halftone parameters is more important than if the viewer will normally be further away. For example, a site sign, a banner or a billboard may be at so great a distance that such details are totally unimportant ... while a graphic on a storefront window will be so close that adjustment of halftones will make a great deal of difference in the appearance of the printed image.
There are any number of factors that can affect the appearance of the printed impression which will be left to each user gaining experience in printing with an Edge. This discussion will be limited to two factors that are directly under the designer's control. They are the size and type of the halftone dots that will be printed.
LPI - Lines Per Inch
LPI is what controls the size of each halftone dot that is printed, regardless of DPI resolution capability of the printer being used. The lower the LPI, the larger the dots. The higher the LPI, the smaller the dots. LPI can be manually set with some halftone types and is automatically set with others, usually based on the overall size of the graphic being printed. There are opposing benefits and pitfalls of this setting. The smaller the dot the less grainy and smoother will be the output, but there is also a reduction of tonal quality which can make the print harsher causing banding lines to be seen and some shifting of colors.
If you are manually setting your LPI for any fill or image, the following are the settings I use:
42.4 LPI - Soft results with rare banding but also grainy if viewed up close.
53 LPI - Better appearing results with reduced graininess but with a slight tendency to show banding lines if gradients are present.
70.7 LPI - Excellent appearing results with slight graininess but with a higher tendency to show banding lines if gradients are present. Some loss of tonal quality details.
90 LPI or Higher - Suitable for emulating the appearance of spot colors with little or no graininess. Harsh banding if gradients are present and significant loss of tonal quality. Some color shifting and generally unsuitable for retaining detail in photos and images.
For other insights, search "LPI" in Omega Help.
Halftone Type
Omega provides a choice of halftone types. Some automatically adjust the LPI based on the output size of the print and some allow manual changing of the LPI setting. These choices vary with the type of object being printed. If it is a filled vector, one group is offered and if it is a raster image such as a JPG or a TIF, a different group is offered. The best way to determine which type best suits your needs and preferences is through test printing.
My preference is to manually set the LPI of each object being printed. For filled vectors I most often use Classical Dot. For raster images and photographs I use GerberTone STC Photo.
For other insights, search "Halftone" in Omega Help.
Testing Your Results
As previously mentioned, to see and best understand how these settings and choices will affect the results, I recommend doing a few printouts using manually inputted LPI settings. For filled vectors, create a vertical column of four 2.75" squares. Fill each with the same process color and vary the LPI settings. Also use different colors for each column from bright to dark such as red, green and blue. For raster images, repeat a photo four times and set the LPI differently for each photo.
