Pixels and vectors
Why does some printed image look pixelated or blurry? And why does the logo have such a small file size as EPS – can I still print it on a poster? PrintCarrier.com explains the difference between pixels and vectors and tells you where to use which format.
What you should know about pixels
A pixel image (also bitmap or raster graphics) consists of pixels, that’s for sure. Common formats are JPG, PNG, TIFF or PSD. Pixel means pixel within a digital image. These single, square pixels are grid-shaped and contain only a single color value, but in their entirety they give a colorful – or even a gray – image. By the way, a monitor also uses such pixels. It has a resolution of 72 dpi, which is 72 dots per inch. One inch is 2.54 inches tall.
Pixels in the magnification
How to: Calculate the resolution or the image size
Now it is obvious that such pixels can not be scaled arbitrarily, without the quality suffers. In order to find out the resolution of a picture and thus its maximum size, we have to calculate a bit.
Let’s assume your image has a resolution of 1548 x 2064 px at 72 dpi. The bill is:
- a) We first divide the width (or height) by the monitor’s resolution of 72 dpi, that is 1548/72 = 21.5 inches (or 2064/72 = 28.6 inches).
- b) Now we convert the inches to centimeters. 21.5 inches x 2.54 = 54.6 cm (or 28.6 inches x 2.54 = 72.6 cm)
The picture thus has a size of 54.66 x 72.6 cm on the monitor.
And how big can I print?
The print has a resolution of 300 dpi. Thus, in step a) we do not have to divide our width and height by 72 but by 300 and reach a picture size of 13.11 x 17.5 cm. So that’s the maximum size of the image in centimeters; if the image is scaled larger, it can be blurred or pixelated.
Those who prefer to leave the arithmetic problem to others can enter their values here.
Among us: Strictly speaking, the image resolution should be in ppi; dpi is the resolution for printing. In practice, however, dpi is used for the image resolution as well as for the print resolution.
How to work with the easy-care vectors
The vector data is easy to handle compared to the pixel data. The formats are the typical EPS, the AI from Illustrator or the CDR from CorelDraw. Vector data does not have to be calculated, nor must the size be taken into account. Namely, vectors do not consist of single, quadratic pixels but of paths, lines and curves. Thus, a line does not consist of lined up points but of a starting point, an end point and a line in between. It is obvious that the quality of this line construction is independent of the start and end points. Vector data can thus be scaled up and down as you like, they can be stacked, stacked and still individually touched and edited. And since you have to work with a lot less points and information, the amount of data is much smaller – and still suitable for enlargement on the poster, if you have worked clean.
This line consists of three points and a connection in between
Even the fox can be wrong
Anyone who now thinks he is a fox, because in the future he only works with vector data and thus saves himself from the arithmetic and possible quality losses, is wrong. Of course, vectors are only suitable for certain objects. Let’s stick to the example of the line – if the line is monochrome, it can remain a vector object. But what if she is to accept different colors? At the latest then you have to work with individual pixels, so with pixel data.
So we have a very clear division of labor. Every photo, every image, every color gradient is a pixel image. By contrast, graphics such as geometric shapes, fonts, many logos or icons are usually vector data.
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