In this post, we are going to venture into another graphic design nerd-out. Don’t worry, I won’t leave you in the dust with techno-babble. This stuff is pretty interesting, and I hope to translate these sometimes difficult topics to laypeople, who might not even know why to care about these things.
With that warning, let’s dive into the world of halftones and gray scale.
Development of halftones and gray scales sprang from the mechanism of printers, which are not as powerful as we like to think. Printers (the machines) have no way to represent the continuous spectrum of color that the human eye or a camera perceives. I’ll explain.
Do a quick observation with me. Look at the closest object, other than your screen. Take a moment to look at the color gradients of the object, specifically the transition between regions of dark and light. These transitions are generally smooth and unbroken. I don’t know about you, but I’m accustomed to looking at things this way. I take it for granted.
Printers (the machines and the craftsmen) don’t always have this luxury in their work. Print machines still print discrete amounts of specific colors. In a red region, it prints red. Making the transition to the slightly different red-orange immediately adjacent is not something that printers naturally handle with grace.
In order to make a print that is convincing to the human eye, complete with the infinite tapestry of colors, textures, and shading, graphic designers have developed ways to translate images into a believable format. That’s where half tones and gray scale come into the picture.
Forgive me if this sounds like a bit of an absurd reduction, but halftones are defined as tones that are neither dark nor light, but lie somewhere in between. Hence, they are half, or some portion of a tone. The best place to observe halftones is in old comic books. Use a magnifying glass for the best results.
When you look closely, you find that what appears an unbroken color is actually a collection of dots. Most of us are familiar with pixels. But half tones employ varying degrees of pixels of a certain color to create that illusion of unbroken gradation that is so familiar to your naked eye.
You can create a similar effect by sprinkling colored sprinkles on a white counter. Areas that have high concentrations of sprinkles appear to be a darker tone of the color and lower concentrations are lighter. No mystery there. That’s what halftones are.
This is the most basic explanation of halftones, and we’ll expand on it, after we look at gray scales.
Just as printers are inherently terrible at printing gradients of colors, they are pretty bad at making gradients of black, grey, and white, without the help of graphic design ingenuity.
This time, let’s turn to the newspaper to understand gray scales. This time, reach for one with no color, hopefully of poor printing quality, since poor printing perfectly presents proper gray scale use.
As you gaze at a black and white picture in the paper, take a close look to see how gradients are accomplished. Just as before, there are varying amounts of black ink to indicate shade and tone. Turn the aforementioned sprinkles black (maybe licorice?) and you can see how this works.
To make dark regions, white dots, or highlight dots, are added to a black background, and vice versa for the lighter regions, which employ shadow dots. This spectrum of gray-ness is where the term gray scale comes from.
The complexity doesn’t end there, and this is where things get interesting. There are several ways to accomplish both gray scales and half tones. Check it out:
Instead of changing the number of dots, you can make half tones by varying the size of the dots, but make sure you say dot gain when talking to designers. They’ll nod knowingly and never suspect that you’re inexperienced in graphics.
Dot gain usually refers to the propensity of dots to get larger on the substrate, and leads to blurry, muddy images. Printers don’t like dot gain and do whatever they can to minimize it.
The standard way to recreate gradients in images is through a spectrum of dot gain, but recently has been replaced by stochastic or frequency modulation (FM) screening, in which dot frequency is manipulated in the creation of half tones.
Output resolution to substrate is pretty important in this. You might remember that screen printing standard for garments is 300 DPI (drops per inch). 300 is plenty for showing the detail of an image, including halftones and gray scale. Most fabrics wouldn’t present the detail of higher resolution very well, so there is little reason for higher output resolution.
This isn’t standard for every medium. The current standard for laser printer gray scale is 1,270 DPI and 2,540 DPI for color, which creates flawless gray scale and halftones on paper, so fine that your eye couldn’t possibly tell the difference.
You’ll probably never get into a discussion about halftones and gray scale with the guys at DFC. These techniques are already built into your image, and the DFC Art Department makes pre-production adjustments to account for dot gain on their own. But if you want to nerd out with them, you can now do so with some measure of confidence.