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Archive for April, 2016

Bitmap vs. Vector Images

Bitmap images are made of pixels. A pixel is a single point or the smallest single element in a display device, be it a computer monitor, TV screen, or your smartphone. Common ways of saving a bitmap image are jpeg, tif, psd, or png formats,

Vector images are mathematical calculations from one point to another that form geometrical shapes. They are commonly saved as eps, pdf, or Illustrator files.

raster_vs_vector

Above you can see the differences between the two, but you cannot always see the difference at a glance. Vector graphics also display an outline or wireframe view which is important for processes that require vector art. (cutting out shapes, embroidery, etc.)

When a raster image is scaled up, it usually loses quality. A raster image can be enlarged by adding more pixels. When this is done you are spreading the original data over a larger area at the risk of losing clarity. The image below shows what it looks like when you enlarge a raster or bitmap image to the point of seeing the individual pixels.

Bird of Paradise.jpg

A vector program uses a mathematical formula to build an image that can be scaled to any size without losing quality.

How large can a raster image can be printed and maintain quality? It depends. I’ve seen 40 pixels per inch images print fantastic because the original image was very good and in focus, I’ve also seen 600 ppi images that looked and printed terrible. A general rule of thumb is 100 ppi at the size you need will produce good results. This is for a digitally printed image not an image that is to be printed using an offset printer.

It is important to understand that you can’t import a bitmap or raster image into Adobe Illustrator and magically make it a vector file. We receive eps or pdf files from customers from time to time that claim that it should work fine when all they did was take an image they found on the internet and place it into Illustrator thinking that would make it a vector file. It just doesn’t work that way.

In conclusion, both types of files will produce good results if they are prepared properly. A vector file is made from mathematical calculations that form shapes—think letters. Bitmap images are made up of individual little squares called pixels—think of photographs.

If you need more info on producing your graphics check out our FAQ’s page!

Why Does It Look Different On My Monitor?

img-gamut

We send color concepts via email to clients for approval before producing any custom project. When they see the final version we sometimes hear them remark, “But it looked so much brighter on my monitor.” Why is that? It has to do with the different way your monitor produces color versus a digitally printed image. They have a different “color gamut”.

What is color gamut? In layman’s terms it is the difference between what the eye can see, what your monitor can reproduce using RGB and illuminated color, and what the printer can do using subtractive color and reflective light. This is very important to understand when speaking with your clients because it gives everyone involved proper expectations going into a project on what is really available and how it will turn out. What follows is a technical Wikipedia description and the movie link gives you a simple visual look at color gamut and how it works.

“In color theory, the gamut of a device or process is that portion of the color space that can be represented, or reproduced. Generally, the color gamut is specified in the hue–saturation plane, as a system can usually produce colors over a wide intensity range within its color gamut; for a subtractive color system (such as used in printing), the range of intensity available in the system is for the most part meaningless without considering system-specific properties (such as the illumination of the ink).

When certain colors cannot be expressed within a particular color model, those colors are said to be out of gamut. For example, while pure red can be expressed in the RGB color space, it cannot be expressed in the CMYK color space; pure red is out of gamut in the CMYK color space.

A device that is able to reproduce the entire visible color space is an unrealized goal within the engineering of color displays and printing processes. While modern techniques allow increasingly good approximations, the complexity of these systems often makes them impractical.

While processing a digital image, the most convenient color model used is the RGB model. Printing the image requires transforming the image from the original RGB color space to the printer’s CMYK color space. During this process, the colors from the RGB which are out of gamut must be somehow converted to approximate values within the CMYK space gamut. Simply trimming only the colors which are out of gamut to the closest colors in the destination space would burn the image. There are several algorithms approximating this transformation, but none of them can be truly perfect, since those colors are simply out of the target device’s capabilities. This is why identifying the colors in an image which are out of gamut in the target color space as soon as possible during processing is critical for the quality of the final product.”

For more information on the different aspects of graphics visit our faq’s page here,

http://www.eventbannersandsigns.com/faq.aspx

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