Halftone Screening is very useful for creating customised dot pitch and angles for rotary and flatbed screens. Once tonal layers are ready for production, this is the final check prior to outputting the file for engraving. The ability to preview the various dot shapes, angles and line frequencies makes this an incredibly flexible tool.
Halftone Screen is in the Filter Browser so that you can apply it alongside other effects such and the Gamma Filter, and Gaussian Noise. If no other effects are needed, you can access Halftone Screen from the Layer Menu.
Instructions
- Open the Filter Browser, and add a new filter set using the small + icon located in the middle of the browser. This will create a new ‘untitled’ filter set for you. This will appear in the top section of the Filter Browser. If you already have filter sets created, clicking the + button will duplicate the selected filter set.
- Select Halftone screening from the list of available filters in the lower section of the Filter Browser.
- Double click on the name of the new filter set in the top section of the browser, and name it appropriately.
Note: Layers should be screened individually to avoid moire effects during printing. If the filter is being used as a design tool, then multiple layers can be screened at the same time.
- Edit the variables to achieve the result you need
- Angle - this applies to the line angle of the dots on the screen. Each layer should have a slightly different line angle to all the others.
- Frequency - this is the line spacing of the mesh. Enter the required line frequency in either LPI or LPC.
- Dot type - Square, Ellipse, Round, Cross, Line, Diamond, Hexagon and Star dots can be created.
- Resize Halftones to fit repeat - this feature zooms the screen so that it fits the destination output and repeats over the joins, pushing the dots together to make them repeat correctly.
In the snapshot below, the original data is on the left, and the filtered data is on the right.
Applying the filter
There are several ways to apply a filter:
- Click Apply - this will apply the filter to the active layer(s), and within a selection if there is one present in your file
- Click Make Layer - this will make a new layer in your file containing the filtered effect, leaving the original layer untouched
- Apply the filter using the Brush Tool - when you have finished building your filter set, simply close the Filter Browser. Then, open the Brushes Library, and select the filter you have just made from the drop down menu shown in the snapshot below. You can now paint with your filter.
Note: The default setting for the Brush Tool is ‘Brush”, located at the top of this drop down menu. To prevent you from becoming confused between the default setting and a filter setting, do not name any filters ‘Brush’. When you have finished painting with your filter, set the drop down menu back to the Brush setting, otherwise the Brush Tool may not behave as you would expect later on.
Applying the filter over a repeat join
For a full explanation on how to use filters, view the Filter Browser article. Each individual filter is further explained in it's own article and can be searched on in the search bar above.
Some of the filters do not work correctly across repeat joins when used in the normal way. Therefore it is important to follow this method to make sure the filter works correctly and does not affect the join. Your design must repeat correctly before you do this.
- Open the Selections Palette.
- Press Offset Repeat. If you are not already viewing multiple repeats of your design, AVA will automatically put your design into s 2x2 repeat when you press this. A selection the size of a single repeat will appear in your file, offset to the first repeat, which is framed in blue in the snapshot below.
- Activate the layer / image you want to filter.
- Open the Filter Browser.
- Apply your the filter. The filter will work correctly in repeat, with no obvious repeat joins. In the image below, the vertical line is the repeat join.
Note: This method does not work for all filters, including Clouds, Waves and Tile. If you need to fix a repeat join using the Clouds Filter, we recommend using a Palette to create a brush which uses a Clouds Pattern, and using this repair the repeat joins.