How to Use Resolution in Digital Signage

Image resolution for digital signage presents a number of questions for our customers. Most of which are simply just a misunderstanding of best practices and marketing messages that are pushed out by television and camera manufacturers. With so many different terms and situations, it’s understandable that users become confused and end up with signage output that is less than desirable. In this article, we will review some of the most popular resolution misconceptions and outline the best practices for preparing images for digital signage.

Misconception #1

If my image isn’t 300dpi, it is not going to look good on my digital display.

Printed output dimensions are dictated by DPI (Dots Per Inch) or sometimes referred to as PPI (pixels per inch) – whatever term you use they basically mean the same thing. This refers to how many pixels get printed in an inch. So, if you have a 600 pixel x 600 pixel image at 300DPI, it will output at 2 inches square. If you change the image DPI to 150, this means it will output at 4 inches square. We will show you how changing the DPI of an image changes it’s printed output size but not the physical pixel dimensions.

Sample A

To demonstrate this point, we created the first example using Adobe Photoshop’s image size tool. You can see that this image’s dimensions are 476 x 224 pixels (Figure A), with a printed document output of 6.611” x 3.111” (Figure B). The DPI (or PPI) is set to 72dpi (Figure C) which is the standard output for Apple Mac displays. (Most Windows computers output at 96dpi)

Sample B

When we uncheck the ‘Resample Image option’ (Figure A), you can see that the pixel dimensions become uneditable (Figure B) and I can only adjust the dpi or printed output of the image (Figure C). By changing the resolution to 300dpi, you can see that the software automatically calculates and changes the printed output size to 1.587”x.747”. No matter what DPI we change in the ‘Resolution’ field, the physical pixel dimensions remain the same.

How Does this Pertain to Signage?

With digital signage, the resolution of the screen is defined by its capabilities to display physical pixel dimensions. Common HD display resolutions are 1280×720, 1366×768 and 1920×1080. CommandCenterHD utilizes common outputs of 1366×768 or 1920×1080, depending on the settings and configuration that you define.

What this means is that your images should be sized no larger than your final output size. The display is unable to do anything with these extra pixels so they are essentially just taking up space.

Misconception #2

Resizing images from their original size shouldn’t affect image quality. This classic misconception is commonly seen in everything from Powerpoint presentations to your neighborhood diner’s menu. There are two common scenarios for this problem…

Scenario #1 Image is set to low rez and scaled larger in the application.

This is by far the most common issue with image resizing. Often times a user will use an image that may not be large enough to properly fill the screen and then stretch it to fit in their software (CommandCenterHD, Powerpoint, Photoshop, etc.). The image will look great when placed into a document at its original size. However, when stretched out larger than its intended size, pixelation and poor image quality will occur.

The image above shows a stretched image in use. This is because the original pixel size of the image is 250×118. When we stretch the image to fill out the 1084×510 area on our digital sign, the image pixels are blown up 4x their original size. The result is a pixelated and unattractive sign! The same principle holds true in print and web publishing. So, how do we get around this? The answer is pretty clear, you need to start with an image that is sized to fit your final output dimensions – success is in the foundation.

The diagram above looks much better than the previous (See the image below for a side by side comparison). I accomplished this by using a 1084×510 image rather than stretching a 250×118 image to fit the space on my screen.

Tip! – Setting the Size in CCHD

In CommandCenterHD, I drag my graphic onto the canvas and then “double click” the image to pull up the sizing options. From here, I can set the image to its exact pixel dimensions (In this case 1084×510). The solution is pretty straightforward but can be difficult to implement if your original image is already set to a smaller size. If you run into this type of situation, it may be best to reconsider how you are placing the image onto the slide or leave it at its original size and tweak the content around it.

While this first scenario holds true with pretty much every medium of output (print, web and signage), the next scenario is geared more towards signage.

Scenario #2 Image is a higher resolution than its final output size.

In print and on the web, you can usually get a way with an image that is sized a bit larger than your intended output size. The downside being that your output sharpness for print or your download quality for web will suffer. Some digital signage players utilize an algorithm that has a tendency to render scaled down images poorly. This issue becomes apparent mainly when you are dealing with an image with a lot of text. The scaled down version essentially removes the anti-aliasing from the text and your digital signage presentation can come off looking choppy (see figure below).

The solution to this problem is the same as with an image that is smaller than the required output size. Create, save and import the image at the size you wish to display on your digital sign. This will ensure the optimal output resulting in smooth text and pixel-perfect graphics!

Image resolution for digital signage presents a number of questions for our customers. Most of which are simply a misunderstanding of best practices and marketing messages that are pushed out by television and camera manufacturers. With so many different terms and situations, it’s understandable that users become confused and end up with signage output that is less than desirable. In this series, I will review some of the most popular resolution misconceptions and outline the best practices for preparing images for digital signage.

Misconception #3

Resolution and Display Size – Does it Matter?

We get asked this a lot. And the answer is, it depends. As you can see by the chart below, the resolution of your displays does come into play the closer you get to the display. So, the closer people are to larger displays, the more important higher resolution displays become to your presentation. If your displays are mounted high up on the wall or far behind an environmental structure, then the resolution does not matter as much and you can save a few bucks purchasing displays with a lower resolution. Additionally, if the displays are small (say less than 20 inches) but in close proximity to the viewer, again, the benefits of a higher resolution display are not noticeable – even to the trained eye.

CommandCenterHD allows you to accommodate custom resolutions in your presentations. Keep in mind that the actual physical size of your images must be considered here. Here is an example:

In this first example, we are showing how the physical size of a 720p image scales within a display set to 1080p. CCHD includes floating point architecture that prevents a full-screen image from showing up like the one you see above on your 1080p displays. That said, stretching a 720p image to 1080p can affect the quality of your image.

This example demonstrates the quality degradation that can occur when a 720p image is stretched to 1080p. The quality degradation may not be as noticeable to the viewer depending on the size of the screen and the viewer’s distance from the display.

Ideally, you want your content to be sized to the exact resolution output of your display. We understand that certain circumstances will require that content is scaled either up or down regardless of its original size. With that in mind, we designed CommandCenterHD to allow users to dictate the size they want for images, regardless of the actual size. CCHD’s unique campaign editor, you can easily, drag n’ drop and resize your content without restrictions of zones or regions.

The information provided in these posts is designed to help our customers make the best-informed decisions when it comes to designing and adding media to their signage campaigns.