Category: Blog Posts

Over the last few years, projection technology has exploded! From the early days of CRT projectors using similar tubes to those in televisions and generating 100 lumens, to projectors that can cover the face of a building, the advances have never stopped coming. Today’s market has a variety of technologies, and most people are still trying to figure out what it is that they are shopping for when they look at the options. In the next few posts I will give a quick run-down of the differences, and what to consider when choosing a projector.

Please keep in mind that this is not an exhaustive discussion of the details, but more an overview to give the average person an understanding of the basics of the technology.

First off, consider the environment. A dark room is very different from a room with full sunlight and the projector will have to be selected to handle that difference. The brighter the room, the brighter the projected image you will need to compete with that light. If you simply shop for price you are going to be very unhappy in the end, if the projector can’t handle the brightness of the space. A screen with direct sunlight is not going to compete no matter what projector you put on that screen. Shadows across the screen will also create a distraction, so having a dimmer area with even lighting (or darkness) over the screen will always yield your best results.

Next, consider your resolution. For those who are not aware of what all of those number refer to, every video image is made up of tiny dots called pixels. When a manufacturer lists resolution they are referring to the number of pixels. These counts are shown by the number of rows and columns. That means that a video image that is listed as 1024×768 will have 1,024 columns and 768 rows. This concept stays the same no matter how large or small the numbers become.

There is a never ending stream of these number combinations that keep coming to the market, but one of the things to watch is the aspect ratio.  This is another method of communicating the resolution, but is more a reference to how many units wide, compared to how many units high. So if your TV screen is 16” wide, it will also be 9” high. The irony of this is that many manufacturers (especially with TVs) refer to the diagonal measurement from top corner to the opposite bottom corner, rather than to the actual horizontal and vertical dimensions. With most equipment you can still look into the specifications and find the actual height and width, but since consumers like simplicity they are sold by diagonal measurement.

If you go shopping for a TV today you are likely to only find 16:9 models at your local store. The older technology of 4×3 has all but vanished from the consumer market, but projectors are still sold in 4:3 as well as other aspect ratios. The 4:3 projectors are typically cheaper, but remember that if you buy a 4:3 projector and send it a 16:9 signal then the available image space is going to be cropped to meet the actual image. What this equates to is the loss of the use of pixels, affecting the actual displayed revolution as well as the brightness. The same is true if you send a 4:3 signal to a 16:9 projector, so the best results that will result in the best bang for your buck is going to come from a projector that matches the signal that you are going to use and the aspect ratio of your screen.

In the next few posts I will explain more about resolution and aspect ratio, and how those relate to formats such as XGA, WXGA or HD formats. We will also discuss the differences in how these images are projected, and how blended image technology has expanded the ability to create even wider or taller images by combining projected images.

Read Part II        Read Par III          Read Part IV          Read Part V

In part I we discussed resolution and aspect ratios. In future posts we will cover additional areas such as the different technologies used to project those images, and other advances.

The combinations of resolution and aspect ratio are summed up in specifications called the format. Designations like XGA, WXGA, WUXGA refer to these combinations. HDTV formats do this as well but include one other designation such as 1080p, 720p, 1080i and 720i references. The pixels on a screen are not changed simultaneously, but scanning across the lines and changing one pixel at a time. This happens so rapidly that the human eye does not perceive the change in this way. In the HD formats the “p” refers to a “progressive” scan that follows line by line from top to bottom. The “i” stands for “interlaced”, meaning that odd numbered lines are scanned top to bottom and then the scan starts over at the top and scans the even numbered lines. A complete cycle, regardless of the format is called a “frame” (with “interlaced” technology it is referred to in “fields”). Frames can be changed in a number of different rates (also referred to as refresh rate or expressed in Hz). This gives the illusion of motion to the human eye.

With computer images a 60Hz rate is common but some gaming systems and higher end equipment may have higher rates. Devices adjust these rates to match, using buffers either in the computer or other playback device. Different content will have different rates that may come from the same device, but the buffer will make the adjustment as needed. For example, a movie might reproduce at 24 frames per second, but a spreadsheet may produce this change only when there is a change in the content of a cell, sometimes once per second or less. A gaming system might have faster action and refresh at 120 frames per second, so a display that refreshes at 60 frames per second will discard half of that data. As long as the signal being sent is below what the display can handle then the projector will be able to handle the display rate. When the rate goes faster than the projector’s refresh rate, then the projector will have to slow it down to meet its own capabilities (if it is able to do so) which will mean the loss of this information and a reduction in the signal. A gaming system that can produce 120 frames per second may still project, but not at its full quality.

The chart below gives a breakdown of some of the more common aspect ratios and their resolutions.

Always remember that you want to find the “Native Resolution” which refers to the actual image produced by the technology in the projector. Any images sent to the projector that are not the same as the native resolution will be adjusted in some way to be able to be projected by that technology. A higher native resolution in a projector will produce a lower resolution being sent to it, but you will not be getting the full capability of the projector. A native resolution lower than what you are sending the projector may also project, but will have a degraded image from the original content. Keep in mind that when you project an image you are blowing up the size of the pixels, so every change in the image is going to show far more on a large screen than it does on your laptop monitor, or even a home TV. Also, just because a projector is advertised as being HD compatible does not mean that the native resolution of the projector is capable of HD formats. What it means is that the projector is capable of altering that signal in order to display it, but not necessarily the way it was sent to the projector.

In the next few posts we will look into the technology used by projectors to display the images.

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Read Part I         Read Part III          Read Part IV            Read Part V

In Part III we discussed the different methods of creating images for projection. In this post we will go over the different light sources.

None of the imaging technologies would be possible without a light source. Brightness in projection is often referred to in ANSI (American National Standards Institute) lumens. It is important to be sure that the rating you are looking at is referred to this way as it is a universal standard put out by a non-profit organization in order to provide an even playing field. Some manufacturers will skirt this definition from time to time in an effort to improve how the projector is perceived.

At present there are three different light sources being used.  Manufacturers are using lamps of various types, LEDs, and Lasers. Lamps are obviously not new. There are a wide range of types, all of which emit heat, requiring cooling systems to maintain the equipment. The downside to lamps is that they will eventually fail. One method to combat this has been to have more than one lamp in a projector so that when one fails the other continues functioning, or can be turned on without going to the projector (usually automatically). Not losing the image for the audience is often the priority, so having another lamp in place is a big bonus, but using them both together can also increase the brightness of the projected image. When you are comparing projectors it is good to keep the lamp type in mind, and also look at how many hours it is expected to last, what kind of warranty does it have, and how much does it cost to replace. Depending on your use of a projector you may need to upgrade your technology before you need to replace an old lamp, but you also may have to spend more on the lamp than to replace the projector with current technology. The other downside to a lamp is that as it ages the color temperature tends to change and the brightness goes down. It is not uncommon for good rental houses to replace a lamp at half of its lamp life in order to maintain good quality for their customers. In this case they will usually retain the old lamp as a backup for emergencies.

LED (Light Emitting Diode) technology is another area that has advanced rapidly in recent years. LEDs are not new and have been in electronics for decades, used on displays to indicate simple things like the power being on or off. When the brightness was able to be increased they began being used in light fixtures and are now being employed as a light source for some projectors. There are three big advantages: the life expectancy on them is incredibly long, they produce very little heat and since multiple LEDs are clustered to achieve brightness, the amount of power needed is far less than with traditional lamps. This is still new to the market however, and is not highly proven in the projection industry. LED projectors often cost more than their counterparts and are used in smaller, less reliable projectors. To gain brightness, most manufacturers are combining this technology with Laser technology in a sort of hybrid, which is also a newer concept and yet unproven.

Laser technology in itself however is just as it sounds. Larger scale projection manufacturers have started to use three different colored lasers as light sources for producing brighter images. The lifespan of the source is virtually unlimited and the brightness is stellar, however the cost is often stellar as well.

So in summary, here are the common options for imaging technologies and light sources. These can be combined to generate various options by a manufacturer:

In the next post we will cover lens selection, and some purchasing advice.

   Email us for special pricing available of all Eiki projectors and Lenses

Read Part I         Read Part II            Read Part III          Read Part V