"Raster or bitmap graphics have to be super high resolution for any kind of printing including screen printing"
When I did color separations for Burton Snowboards in Burlington, VT we used 25 lpi for a bunch of reasons. One of which was we needed to “embrace the fiberglass” meaning it’s a crummy surface to print on so dumb it down. The fact was that the surface wasn’t able to hold a smaller dot so bigger dots were in order.
Screen print graphics can be very forgiving and 150 dpi is fine for our forgiving graphic industry. In some cases even lower depending on content of the image, the individual shops capabilities and of course the tolerance of your customer.
In general I color separate index color at 150 to 180 dpi. 200 dpi for simulated process (unless i’m delivering a graphic that needs to be resized up by the customer).
Since we use open enough mesh for ink to get through it, our dpi doesn’t need to be that high and in fact, by the time ink hits cotton the dots have spread in size and the garment doesn’t know the difference between 1200dpi and 125 dpi.
There are so many controllable and uncontrollable random things that can happen in the print production process that a high resolution image isn’t going to translate as high resolution. Any dot higher than 65 lpi will just go right through the screen ultimately and you loose your fades to ugly, choppy banded images.
In general I use 45 to 55 lpi in a halftone situation. Sometimes 65 lpi if there’s alot of detail and the screen guy is comfortable with it. And sometimes as low as 35 lpi depending on the application. Like the snowboard graphics. But never 2400 dpi 133 lpi magazine graphics. Cotton doesn’t know what to do with them for sure and screen fabric plain old can’t hold the dot for more than one squeegee pull.
So high resolution for screen printing is a definite myth!