First, let’s define it:
Halftone is the technique used to reproduce photographs or images through the use of dots, varying either in size, in shape or in spacing. “Halftone” can also be used to refer specifically to the image that is produced by this process.
Then, let’s talk about it!
The human eye can actually distinguish millions of shades of colors. In order to create a full color image that contains an array of colors (too many colors for a single screen printing press) or to re-create images that contain shades and gradients that blend evenly, you need to use halftones. Halftones used in full color process require a set of 4 colors known as Cyan, Magenta, Yellow and Black (CMYK) which you can think of as your “primary colors” (Cyan=Blue, Magenta=Red, Yellow=Yellow). When you overlay these colors they can create secondary colors such as Orange, Green and Purple.
By using tiny, pixel sized dots when you overlay these colors, you can create an optical illusion that makes it appear as if you used several, to hundreds of colors, to print one image – while in reality, only 4 colors were used.
This method of halftone blending was used in the first color TVs (although televisions used Red, Blue and Green – not Cyan, Magenta and Yellow) and is still used for newspapers, books and generally any color computer printer. (That’s why you always have to buy 4 cartridges when your printer runs out of color ink!)
Halftones can be any size or shape. The most common shapes are circles, lines, diamonds, squares, ellipses and crosses. These shapes can be used simultaneously to avoid Moiré, tone-jumps and loss of highlight dots.
The photo below is an example of the optical illusion seen through the use of CMYK halftones:
Now, let’s take a closer look!
The round object in this photo is called a Loupe, it’s used to view film negatives before exposing and developing. It’s basically a 10x magnifying glass. With the use of the loupe, you can see each individual halftone dot, and how it overlays the next to create the illusion of different shades:
This image was printed using Water Based Enviro Process Inks Cyan, Magenta, Yellow and Black.
The halftones were achieved through the use of the BLACKMAX system.