Photo separation for screen printing: index separations, free
Turn a full-color photo into 2 to 8 spot-ink films with a white underbase for dark shirts. Free, and nothing is uploaded. Every square of the print gets one ink, scattered so the inks blend into the photo's colors.
Stays on this computer · no signup · no watermark
Faster with the free Chrome extension: right-click any picture on a website and send it straight to the photo separation tool. Add to Chrome · what it does
Extension installed. Right-click any picture on a website and choose Makerfern → Open this picture in… to bring it here.
A photo on a shirt, with spot inks
The color separation tool splits logos and flat artwork into inks, but a photo has thousands of colors. This tool makes an index separation instead: it picks the photo's main colors as inks and gives every square of the print one of them, scattered so they mix by eye. You get one film per ink at the size you will print, with registration marks and a label on each.
What you see
- On the shirt: the whole print on your shirt color, as it looks from a step back.
- Up close: a small part of the print, enlarged, next to your photo at the same spot. Each square is one film pixel with one ink; from a normal distance they blend.
- Your photo: the photo as you loaded it, to compare.
- Films 1, 2, 3…: each film as it will print, black where the ink goes.
What you get
- One film per ink: a 1-bit PNG at the film resolution you pick, solid black on clear, with registration marks and a label.
- A white underbase film for dark shirts, under every ink except the dark ones.
- One PDF with a film per page at real size, and a print sheet listing the films, all together in one zip.
- A plain backdrop left out: a photo on a white page prints only the picture.
What it does not do
- It makes index separations only. It does not make simulated-process, CMYK or halftone separations.
- It has not been tested on a press by us. The resolution, the number of inks and the print order are starting points: print a test before a run.
- It does not match Pantone or other ink colors. The inks are the colors in your photo, shown as hex values.
- The preview shows each ink as a flat opaque color on the shirt color. It is a check on the separation, not a simulation of ink on fabric.
- The longer side of the print goes up to 24 in. A very large print at a high resolution is made at a lower one instead, and the page says so.
Before you expose a screen
- Print every film at 100% on film positive or transparency, as dark as your printer goes.
- Measure the first film: the marks are 8 mm outside the photo, so top to bottom is the photo's height plus 16 mm.
- Stack the films on a light table and check the marks line up.
- Burn the screens. Not sure of your exposure time? Test it first with the exposure calculator.
Questions
What is an index separation?
A way to print a full-color photo with a few spot inks and no halftone dots. The photo is turned into a grid of tiny squares, and every square gets exactly one ink, or the bare shirt. The inks are scattered so that, from a step back, they blend into the colors in between, the way a few colors of thread or tile can make a picture. Each ink has its own film and screen, and no two inks share a square.
Is this a simulated process separation?
No. Simulated process prints soft, overlapping halftoned colors, usually made by hand in Photoshop or with paid separation software. This tool makes index separations only: square pixels, one ink per square, no dots and no overlap. Printers often call index separations forgiving, because the scattered squares hide a small shift between screens, but the look is grainier than a well-made simulated process print.
How many inks should I use?
Between 2 and 8, plus a white underbase on a dark shirt. More inks follow the photo more closely; fewer are quicker and cheaper to print. Start with 6 and look at the print up close: if the colors look right from a step back, try fewer.
What film resolution should I use?
The resolution is the size of the squares: at 200 dpi each square is 1/200 in. Smaller squares look smoother, but the screen has to hold them, which takes a fine mesh and careful exposure. 200 dpi is a starting point, not a standard: ask your printer what their screens hold, and print a test.
Do I need a white underbase?
On a dark or colored shirt, usually yes: ink is slightly see-through, so light colors printed straight onto a dark shirt look dull. The underbase film puts white under every ink except the dark ones, which show on the shirt as they are. On a white or light shirt you do not need it, and the tool leaves it off.
What order do I print the films in?
The underbase first, if there is one. The ink films never overlap, so their order is yours to choose: the tool lists them darkest first. Follow your own press routine for flashing the underbase.
Which photos work best?
A sharp photo with good contrast and at least 150 pixels per inch at the print size. A photo on a plain backdrop works well: the tool leaves the backdrop out, so only the picture is inked. A very dark photo on a black shirt mostly disappears, and the tool says so: pick a lighter shirt or a brighter photo.
How do I get the films made?
Print each film at 100% ("actual size", never "fit to page") on film positive or transparency, as dark as your printer goes, or take the files to a print shop. Each PNG is 1-bit black on clear with its resolution stored in the file; the PDF has one film per page at real size with the marks and labels as vectors. The registration marks sit 8 mm outside the photo on all four sides, in the same place on every film.
Does it match Pantone colors or my inks?
No. The inks are the main colors in your photo, shown with plain names and hex values. Mix or choose your inks to suit, and treat the hex as a guide to what each film is for.
Is my photo uploaded?
No. The photo is read, separated and written into the films in your browser, and the files are saved from memory on your device. Close the tab and nothing is left.