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The images posted appear to be posterized halftones over a tinted underbase, rather than white underbase.
fred
Ok Fred...how do create a posterized halftone?
And once the posterized halftone is created, do you just screen print the image using a dark ink on top of a solid light color underbase to achieve the effect below? But, how do you separate the dark and light colors before screen printing?
Last edited by rockwell; February 16th, 2008 at 02:38 PM.
In photoshop, you would delete away the outside of the image. Using the deleted pixels as a selection, a new layer can be made using the inverse of the selection.
The simplest way to posterize an image is to converted to a grayscale, then using the levels command, pick a central point to position both the black pointers. (see attached)
From the b&w image on the upper layer, delete the white to expose the mask layer below it.
Fred
Let's put the posterizing aside for a second...I just cut out a photo, then created a new layer of the same image. I selected on the new layer and inverted the image, now I'm not sure how to proceed? At what point can I change the layers to sold dark & light colors?
BTW: I also have a third layer that is a solid white background.
Thanks for your help Fred! Remember, I'm still a Photoshop newbie...
You think it is hard for you?, try it from the other side!
A picture is often worth 1,000 words, so i've attached a photoshop file which is setup for 2 color screen printing.
fred
I feel I understand the concept behind creating a 2 color halftone, I just don't know actually do it myself in PS. Cut out an image, take negative leftover space and create solid background, halftone the image and layer it on top of the background. I can create B&W halftones all day, but this is proving tricky for me.
Is there anyway way you please could just list the steps in numerical order like you were starting from scratch? I'm hoping to have this project completed by Monday, and so far you are my only lifeline. Thanks bro.
I've added a second channel and named them color 1 & 2.
In spot color 1, i've created a silhouette of the artwork using the clipped image. i've pasted a copy of the color image into the spot channel 2.
with only spot channel 2 visible, you should see a grayscale tiger. If you do, press control-L for levels. Move the outer pointers to a common mid point as displayed in an earlier graphic. Press OK.
Now click to make spot color 1 to be also visible. This should display a purple eyed cat with a yellow for the light color and white for the background color.
Just with the levels command, you should be able to change the graphic i sent back to look similar to this attachment.
Try it and let me know you get it or if you get lost.
Given the nature of the graphic, i would not use the levels to make the halftone, but i don't to confuse you. We also need to discuss trap.
fred
I just added a second spot color, but am not sure how create a silhouette of the artwork in spot color 1?
I've added a second channel and named them color 1 & 2.
In spot color 1, i've created a silhouette of the artwork using the clipped image. i've pasted a copy of the color image into the spot channel 2.
with only spot channel 2 visible, you should see a grayscale tiger. If you do, press control-L for levels. Move the outer pointers to a common mid point as displayed in an earlier graphic. Press OK.
Now click to make spot color 1 to be also visible. This should display a purple eyed cat with a yellow for the light color and white for the background color.
Just with the levels command, you should be able to change the graphic i sent back to look similar to this attachment.
Try it and let me know you get it or if you get lost.
Given the nature of the graphic, i would not use the levels to make the halftone, but i don't to confuse you. We also need to discuss trap.
fred
I added a silhouette of the artwork in spot color 1 and copied the image into spot color 2. I then selected on spot color 2 only and pressed control-L for levels and I moved the pointers in toward the center (are the levels adjusting the amount of color that will penetrate?). I guess I'll have to figure out what will work best.
Ok, I now have an orange and gold tiger...BUT at this point no halftones have been created? Also, what is a trap?
I hope you have a postscript printer. If you do, you can simply go to the print menu and print separations. In the printer driver, the spot color channels would transform to haldtones, but using this simple posterization technique, no halftone dots will be generated.
che guevara is a classic example of a simple threshold posterization.
If you left the image as a grayscale, it would produce a traditional halftone dots, but would have color, but would use the second color for a background.
Trap is needed in printing to cover the imperfections of the printing process. On spot channel 2, you need to either expand the silhouette a to create a halo around the image or the silhouette needs to be shrunk a little to prevent a partial halo's. Simple use the magic wand on the tiger and expand the selection to create a halo, or select the background and expand it to prevent halos. In the sample you posted, the expanded the background, then appeared to purposely misregister a little bit. (the colored edge on the pants).
I'd suggest you play with filters on color 2. Such as
Double click on the spot channels and click on the color swatch and find some better colors.
fred
I don't have a postscript printer, just a simple inkjet. Before I send my artwork to my screen printer though, I'm going to have to convert it to halftones somehow. I've never encountered this before, because I've always worked with 1 color halftone prints. Is there any way to create halftones at this stage of the process without it being done by a printer?
Pertaining to Trap...I was wondering why the background color in a 2 color Halftone design is usually slightly larger...now I know. I'll get to that later...
Because the file is setup in spot colors, your artwork is basically ready to be sent to a screen printer to produce film and print.
If you wanted to separate the file yourself, you would want to turn off all the colors except 1 spot color. Then under image->mode->bitmap, you can transform a single layer into a bitmap.
For output resolution, match your printers resolution. Under method select halftone screen, then in the next dialog select 45 LPI/45 degree.
fred
Ok...so I could send the artwork as is, and tell my printer that I wanted the halftone 55 LPI/35 degree or whatever and it should be cool?
Now...I'm going to go back and work on the getting the levels and the trap set properly. I may hit you back again, but not tonight. Thanks again for everything Fred, you've been a HUGE help!
Because the file is setup in spot colors, your artwork is basically ready to be sent to a screen printer to produce film and print.
If you wanted to separate the file yourself, you would want to turn off all the colors except 1 spot color. Then under image->mode->bitmap, you can transform a single layer into a bitmap.
For output resolution, match your printers resolution. Under method select halftone screen, then in the next dialog select 45 LPI/45 degree.
fred
Hey Fred...I have a couple of follow-up questions for you:
1. When I add spot colors to a design in Photoshop and save the design as a .jpg for preview, the spot colors never save? I've tried flattening the design and they still won't save...is it possible to save them as a .jpg?
2. I've been reading more about posterizing on this forum, and I think I've found an alternate method that doesn't involve the levels command:
Open image
Image...Adjustments...SATURATION
Image...Mode...GRAYSCALE
Filter...Other...HIGH PASS
Image...Adjustments...CONTRAST & BRIGHTNESS
I'm not sure if the steps above are actually considered posterizing, but they achieve the same effect to me...ANYWAY, my question is...using the method above, is it also necessary to then halftone the image before screen printing? It seems the image is now made up of solid colors, so halftones are not needed...am I correct?
How to create 2-color Halftone? 
