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If you are preparing graphics for printed materials to be sent to a black and white printer(not a grayscale) that uses halftones to reproduce grayscale, is there anything I can do to optimize the final quality.

Usually I would do the basics, make sure my resolution matches the print resolution and make sure my number of colors and CMYK/RBG matches the printer. However there's not really a number of colors or number of grayscale increments.

Doing the halftone in advance seems like a bad idea. I assume that if I apply a halftone effect to the image then that'll make it worse. I.e. my halftone probably won't match the configured pattern or error haltone algorithm of the printer, and therefore it will be halftone applied to halftone, kind of like dithering twice.

I'm wondering if I should send twice the image resolution, i.e. send 1200dpi for a 600dpi print, to give the printer's halftone algorithm more neighboring pixels to work with when it samples it down to halftones.

Everything I've seen online when searching applies to screenprinting and faking a halftone effect. I don't think that applies because if I send an image with a halftone effect already applied, then it's just going to get the printer's halftoning applied which will further degrade the image.

It seems like I should be sending the best quality image I can with as little/no dithering(and no halftoning) so that the printer's halftoning algorithm has the best to work with.

What would you recommend as techniques to optimize image quality to maximize output from a printer's halftoning?

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  • Most black and white printers are 2 colored and use halftones. I am not aware of any sublimation dye printer that does just bw but it might exist. Dont sen double the native size of the printer figure out your LPI value and double that
    – joojaa
    Jun 4, 2018 at 18:55
  • What kind of quality problems are you encountering? As others point out, as a designer you shouldn't normally do anything to account for halftoning, but there can be special cases.
    – Wolff
    Jun 5, 2018 at 9:51
  • What are the dimensions of the image in pixels? What size will the image be when printed? If quality is a problem, I suspect it's because you have a low resolution image - but that's only a guess. Can you please add details to your question, thanks.
    – Billy Kerr
    Jun 5, 2018 at 10:29
  • @BillyKerr I have source vector graphics so I can output any resolution. I have tried 600dpi greyscale to match the print output, but the halftoning degrades the quality significantly.
    – AaronLS
    Jun 5, 2018 at 15:42
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    If you have vector then why convert to raster? And what is exactly the problem you are encountering?
    – Wolff
    Jun 5, 2018 at 23:01

2 Answers 2

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On the designer's end you don't address halftones for production in any way.

Send a high PPI image, that's all. The print provider will know how to best handle halftones to achieve optimum results on their equipment.

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  • well you could make a huge bitmap with native print resolutiona and design your own halftone
    – joojaa
    Jun 4, 2018 at 18:56
  • Thank you, this is what I suspected Scott, but our vendor basically is throwing up their hands and saying the quality is our problem, but has given us the list of halftone algorithms their software supports. I'll probably accept this as the answer unless someone else has a better suggestion.
    – AaronLS
    Jun 4, 2018 at 19:24
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    Well, I'd find a new printer. But.. you could, as Joojaa alludes to, halftone the image directly so it is no longer a continuous tone image. Which means it would print as 100% color, no screens. But, should the frequency you use in the image not match the output screen frequency of the print provider, you could get double halftoning making things much, much worse. In several decades I've never had a decent printer "throw their hands up" if I was not satisfied with output quality.
    – Scott
    Jun 4, 2018 at 19:27
  • Yeh, the double halftoning is what I was worried about if I tried to send a pre-halftoned image, but it is worth a try.
    – AaronLS
    Jun 4, 2018 at 19:47
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Any printer on the planet, with the possible exception of sublimation printers, send the images as "black and white"

There is no grayscale printer on the planet.

that uses halftones to reproduce grayscale

Halftones are one of several options to send an image to simulate grayscale. Other is error diffusion or stochastic pattern, the one used on digital printers, for example, InkJet based printers.

So. If you simply send a grayscale image to a suited system it will render a halftone, for example, plates for offset print.

In some cases, when you really know what are you doing, you could ask for specific settings, for example:

  1. Higher density LPI. The normal output could be 150 LPI at 2400 DPI with a File of 300 PPI.

You could ask for a 200 LPI Output on a 3200 DPI printer using a 400 PPI file.

But I am assuming that you already know that the LPI depends on the printing system and paper to be used... Of course, you knew that.

  1. Different dot shape. Round, diamond, rectangular, oval, linear...

  2. Specific angle.

  3. Different rose pattern.

Reading more deeply your question, you need to remember there is a direct correlation between the DPI of the printer, the LPI, and the Grayscale tones.

The basic correlation is

DPI/LPI = Grayscale tones.

Do not send a 600 DPI 1-bit image, because the dots produced are a lot rougher than the native produced ones at 2400 DPI.

Sending a 1 bit image will render the dots exactly as they come on the file.

So you could send a 2400 PPI 1-bit image with your already halftoned image. But I really doubt you can produce a really well-defined halftone. I have not seen a good and flexible enough plugin for Photoshop to define it really well print production ready. Only "fake ones" or esthetically defined ones. How can I simulate a 300DPI printout on a 600DPI printer?

send 1200dpi for a 600dpi print

Nop, you can not, should not do that.

You only double the resolution PPI from the file to the final LPI. This is a 8-bit image that will be transformed into 1 bit output.

You can not double the PPI on one 1-bit image to the DPI output. You will make a mess of a file. You can send the exact same DPI.

In specific cases, you can send a 1-bit image as an exact submultiple of the output DPI.

On a 2400 DPI print send 1200 PPI file (1/2)

800 PPI (1/3)

600 PPI (1/4)

480 PPI (1/5)

400 PPI (1/6)

300 PPI (1/8)

We probably need more information to see the specific problem.

P.S. Remember and have this perfectly clear.

PPI are different units than DPI.

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