Silkscreen – Just an Introduction About Image Resolution

This article is just a small compilation of samples from an e-book sold on this website, whose first edition is available in Portuguese language, and licensed under CC BY-NC 4.0.

The definition of a digital image encompasses all genres originating, manipulated, or stored in electronic format – characterized by a strictly visual state, without physical or tangible form. However, in the context of graphic arts, it is common to opt for a pertinent differentiation between digital image and graphic image, considering the direct and significant influence that this difference implies in distinct printing techniques. Following this, the term “digital” ends up being more associated with photographic images or those structured in pixels, while the term “graphic” is linked to flat or vector images. Both types are still electronic formats, but with completely different structures.

Image Resolution – Digital and Mechanical

Meanwhile, a large part of digital images are intended for printing on substrates – the transition from the intangible to the tangible mode, or from the digital to the mechanical. And just as with screen printing, this process also has a geometry. Whether in print or digital terms, this geometry is summarily referred to as resolution. Resolution translates the level of detail in an image, defining its degree of sharpness, in an inverse proportional relationship – because the greater the detail, the lower the overall sharpness. To measure image resolution, indicators are used that have ended up succumbing to the simplification characteristic of modern times, which, for that reason, is not always beneficial to understanding processes.

Unlike the human eye, which captures the image in a continuous, permanent way, graphic environments have tools capable of reaching the detail of the image, establishing the distinction that separates that which is digitally generated from that which is mechanically reproduced, resulting in two distinct units – the pixel and the dot, respectively. The big question in this distinction is that the notion of dot is systematically shared in different origins, justifying a clarifying approach to the four resolution measurements relevant to the screen printing context – PPI, DPI, LPI and SPI.