In the LED: Pitch and "Pitch"

There are several factors that affect the actual image quality of an LED display system. These include resolution, lamp quality, processing and pitch with the latter being the most common reference point when evaluating systems. The reason this is important is because LED display systems are typically estimated with pitch as the defining specification for resolution. The higher the pitch, typically the higher the resolution.

To get a better understanding of this, it’s important to define “pitch” – which is the millimeter distance between pixels on a center-to-center measurement. Therefore, a 10mm display means you have 10mm from the center of one RGB (red/green/blue) pixel to the center of the adjacent RGB pixel, with that same measurement reflected when you measure red lamp to red lamp and the green and blue lamps as well.

As you peruse various manufacturers' specifications, you will find that the pitch measurement is usually rounded off. In most cases, manufacturers will round pitch to the nearest whole number, so if their pitch is actually 10.7mm, it will be marketed as an 11mm. In other cases, some manufactures opt for stretching the truth a bit and market the 10.7mm pitch as 10mm. On smaller displays, that .3mm difference in pitch won't usually affect the overall performance or price of let’s say a typical 120x240 LED display other than perhaps some variances in cabinet dimensions. The bottom line is that you are essentially getting what you paid for whether the estimate quotes you a 10.7mm or 11mm pitch LED display.

However, when your display requirements call for larger sizes, you will notice a very unacceptable difference in total pixels as the .3mm differential expands exponentially. A good example of the affect is akin to inadvertently making the lines on a football field 2" wider than normal. With the expanded line markers every 5 yards, the playing field stretches from 300' to almost 303-1/2'. In the display world, this means that you are not getting all the 10mm pixels you paid for! The 10.7mm display being marketed as a 10mm display translates into losing thousands of LEDs – but you are being quoted to pay for those missing lamps. And the larger pitch 10.7mm display will have far less resolution than the true 10mm display. So the first rule of thumb is to always check the precise pixel count when comparing manufacturers' quotes. Estimating variances can translate to higher costs and lower resolution so don't leave your money on the table.

How you measure pitch is also as equally important as what you are measuring. Some manufacturers have gotten creative with their marketing, and have opted not to use the industry standard center-to-center pixel measurement. They measure the smallest distance between lamps in a column or row measurement – and not the actual distance between individual RGB LEDs as the official "pitch". Therefore, a display with an actual 25mm center to center pitch may be marketed as a 17mm "pitch" when measuring distance from the edge of the lamps, and customers incorrectly assume that they are being quoted a "17mm" display. Once again, the best way to verify pitch counts is to make a quick comparison between the total number of lamps for each of the LED display being quoted. The difference in lamp count between a 25mm and 18mm LED display will be significant as will the images each is capable of displaying.

If overall display sizing is an issue, and (if you recall from my previous article) you want to achieve the defined minimum total pixel count of 30,000 pixels for text/graphics and 50,000 for quality still images and video, the only way to reach these minimum targets is to tighten up the pitch to allow for more pixels within that limited area. For example, if you have an approximate 4'x8' display area, you need a 10mm display with a matrix of 128x256 to put you just over the 30,000 benchmark for text/graphics; however, you need to tighten the display pitch to 8mm with a matrix of 176x288 to hit just over 50,000 if you need high quality still images and video.

The bottom line is, the tighter the pitch, the greater the resolution and the better the image quality! Always double check and verify the actual lamp and pixel counts to make sure you are being quoted the LED display you need and will ultimately be paying for.