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If you're doing an A2 screen print must use the ink jet printers in the print resource room. They work with a different technology: still create a positive for each ink and a half tone screen but a different process.
Photoshop: colour channels: menu: Split Channels:
-each channel will be split into an individual photoshop document.
Tonal Varitation: To print as a tint of the ink you will need to make it into a grid of dots yourself.
Image must be grey scale.
Image- Mode -Bitmap (one of the earliest digital image files, much simpler- pixel is either black or white.)
Resolution value: for this process we work at a higher resolution than 300: 1200 so that we preserve the detail.
Method: Use: 50% threshold - choose whether their black or white.
Method: Use: halftone screen - that will maintain all of the different shades of grey but will turn to dots. (need this one for screen printing, printing etc.)
Halftone Screen: Frequency: around 50, Angle: 15,75,105,155 (screen print angles). Only one ink needs a half tone screen so it will just be 15.
Shape: Round (usual one)
If you have a positive where there is no tonal variation, do not apply a bitmap as you may start to see dotty edges instead of a sharp one.
In illustrator only change the frequency and the angle if you are working with a tint.
Different file for each one of the inks in photoshop… if then you want to change it, then you have to go back to your original image and apply it all again… however if your working on illustrator you can edit the file and then reprint (much more flexible process.)
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Flattened image: Select a range of colour: colour range: sample orange
Select: Colour Range: sample colour
If you want to see the original image press command.
If you want to see the selected area on the original image change selection preview to greyscale.
Fuzziness: highest
Get a selection of the entire colour chosen.
Channel: New spot Channel: If your screen printing you don't need the pantone reference system, need the picker: pick one that represents the ink you will use.
Naming the channel: Include the word 'spot', you will already have other channels for example, magenta black etc in CYMK. Differentiate your spot channels!
Solidity:0 (represents transparity of the ink.)
Now the image won't represent what the image will look like when its printed. (CYMK + spot shown)
May need to clean up your spot channel if you have over selected.
Image- Adjustments- levels- can get rid of any parts you don't want to print with that ink by adjusting brightness etc.
Can use the same process for the other colour inks. May be easier to turn off spot colour, ensure when you select the colours first that CMYK layer channel is selected.
For your black ink you could just use the existing K channel.
You may want to use one of the other CMYK channels for a new ink - they may represent where you want to apply the other colour ink.
Right click on channel + duplicate it.
Double click on thumbnail of channel and you can change it to a spot colour and change ink to appropriate colour - Black - C=0 M=0 Y=0 K=100
Solidity: 100
Make sure it has 'spot' in the title.
This all means that you can now change the colour of this selection if you need to.
Can duplicate C for example and then modify the channel on levels- this means you don't even have to make a selection.
Click on CMYK again.
Select- Colour Range
Select the next colour (perhaps lighter colour - reduce fuzziness to lowest.)
Once you have a selection you can modify that selection. Select -Modify - Expand or Contract.
Expand - help make the selection a bit bigger so that you will get a slight overlap between inks so that the registration will be more forgiving if you misregister. Depending on the size of the image will depend on how much you will expand- trial and error if not sure how many pixels to expand by.
New spot channel - name it. Deselect CYMK. Change colour, solidity: 0.
Slight overprint between inks to minimise misregistration - trapping.
Once you've made your channels you can paint in the slight overlap/clean things up.
Make sure your painting on the right selected channel and full opacity, can use the black pen.
Stacking order of channels represents the order they will be printed. Always duplicate the black so that it always appears on screen was the last ink printed- helps to simulate printed process on screen. Bottom- printed last, top- printed first.
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In order to make a positive you must fill the coloured layer in black.
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If you have a layer that has transparency - hover mouse over layer, press command and click on thumbnail, will select it.
Make a new spot channel - will reproduce that selection.
Image -Mode- CMYK - dont flatten - Creates a black for you. Black may be made up of a little bit of each one. Modify K channel - Duplicate - then double click on that spot colour and change to spot colour, colour black : solidity 100% and C=0 M=0 Y=0 K=100
Image- adjustments - levels
If its smaller than a3 put into illustrator print the positives,
If its bigger than a3 split the channels and print each one individually.
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Make selections based on the ink you're going to use
Command key and shift key when clicking on layer which will allow you to add this to the selection
If you hold alt it will remove. Shift will add.
If we are working with layers - Make another layer above original - choose a colour - only works if working with transparent layer- hold alt key as you move over the gap between the two layers - you will only see the colour where the pixels are below.
If you loose channels menu it will be in Window- channels.
Edit- Fill - can fill selection will a colour.
Save as tiff or psd
For blog: Save as: Jpeg won't include the spot channels. So instead you may need to take a screen shot.
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Command click on a channel will select everything on that channel.
If you want to delete a particular colour from overlaid colours you click on the main colour you want to keep and select. Then click on channel you want to delete from overlaid colours. Delete. and replace contents with white.
Invert - Image - adjustments - invert.
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