Match the dots to your mesh, pick an angle that will not fight the threads, and export black dots for your films. With the numbers that actually matter.
Open the editor with this effect
A screen cannot print grey. Each part of the mesh either lets ink through or blocks it, so every shade in a photo has to be faked with dots. A good halftone is the difference between a print that looks like the photo and one that looks like mud. It comes down to three choices: how fine the dots are compared with your mesh, the angle of the rows, and making sure the smallest dots survive on the screen.
Lines per inch, or LPI, is how many rows of dots fit in an inch of the print. The common rule of thumb is that your mesh count should be about four to five times your LPI, so each dot sits on enough threads to hold.
As a starting point: 110 mesh holds around 25 LPI, 156 mesh around 30 to 35, 200 mesh around 40 to 45, 230 mesh around 45 to 55, and 305 mesh around 55 to 65.
Most shirt printers land between 45 and 55 LPI on 230 mesh. Go coarser for textured or heavy fabric, for plastisol on dark shirts, or while you are still dialling in exposure. Coarse dots are far more forgiving.
Too fine for the mesh and the smallest highlight dots fall through the gaps between threads and never expose, while the shadows fill in and go solid. If your highlights blow out and your shadows clog, your LPI is too high for your mesh.
Moire is the wavy, checked pattern you get when two regular grids overlap. On press, the two grids are your dot rows and the threads of the mesh, which run at 0 and 90 degrees.
For a single colour, most printers angle the dots at about 22.5 degrees, which keeps the rows well away from the weave. Bitgrain sets the angle in steps of 5 degrees, so use 20 or 25. If a pattern still shows on press, rotating the art or the angle by a few degrees usually clears it.
When you stack several halftoned colours, each one needs its own angle, spaced about 30 degrees apart, so their grids do not beat against each other. The CMYK style in Bitgrain does this for you, with screens at 15, 75, 0 and 45 degrees.
Round dots are the standard and the easiest to hold on a screen.
Ellipse dots join up into chains around the middle tones, which smooths out the jump you sometimes see where round dots first touch. They suit skin and soft gradients.
Square and diamond dots look more graphic and print a little heavier. The line screen turns the image into rows of lines, like an engraving, and is very easy to expose.
On a light shirt the halftone is simple: dark ink dots, with the shirt as the highlights.
On a dark shirt, a one colour white print works the other way round. The shirt is your shadows, and the white dots are biggest where the photo is brightest. Set the Page colour to black in Bitgrain to see it this way, then export a transparent PNG of the white dots for your films.
Colour prints on dark shirts usually go down on a white underbase. Many printers halftone the underbase too and choke it in slightly, so it softens the hand and stays hidden under the colours. That step lives in your separation software, but the same LPI and angle rules apply to it.
Bitgrain makes a single colour halftone screen, a colour halftone, or a four screen CMYK halftone. Four colour process on fabric is hard to hold, so most shirt printers stick to one or two spot colours.
For spot colour work, the Print layers export splits a photo into up to four inks, one file per ink, up to 2400 pixels on the long edge. It is built for risograph, but it makes a quick starting point for a small two or three colour piece. For full simulated process jobs, dedicated separation software is still the right tool.
To see how a one, two or three ink design will look on a real shirt, Drapeshot, the Bitgrain mockup tool, has stencil, two colour and three colour looks you can try on tees and hoodies.
Open the editor from this page. A mono halftone is already applied to the sample, so drop in your own photo.
Work out the dot spacing for your mesh. Divide the image width in pixels by the print width in inches to get pixels per inch, then divide by your LPI. A 3600 pixel wide photo printed 12 inches wide is 300 pixels per inch, so 50 LPI means dots 6 pixels apart. Set Dot size until its readout shows that spacing.
Under Advanced, set Angle to 20 or 25, pick a Shape, and push Sharpness to 100 so the dots have hard edges for exposure.
Export a PNG with Transparent background on, or on Pro an SVG. Print it on film as solid black, and check the smallest highlight dots on the film before you burn the screen.
Divide your mesh count by four or five. On 230 mesh that is roughly 45 to 55 LPI, on 156 mesh roughly 30 to 35. When in doubt go coarser, since coarse dots hold much more easily.
About 22.5 degrees is the usual choice for one colour, to stay clear of the mesh threads. In Bitgrain use 20 or 25 degrees. 45 degrees is the classic print angle and works too, but it is more likely to clash with the weave on press.
Bitgrain fits up to 600 rows of dots across the long edge of an image. That covers 50 LPI on a 12 inch print, or 60 LPI on a 10 inch one. Free exports carry a watermark and stop at 1080 pixels, so film ready files need Pro.
Yes, on Pro. When halftone is the last effect in your stack, the SVG export saves every dot as a vector, so it prints sharp at any size and opens in Illustrator, Inkscape or Affinity.
No. The halftone is a classical screen calculated from the brightness of your photo, and it runs entirely in your browser.