Keystone or No Keystone? That is the question!!

Apr 27 2012


I was recently talking with my nephew about correct projector installation procedure. After a few minutes we ended up in a conversation about one part of the installation in particular…Keystone!.


He asked me, “Mark, should we use Keystone when installing a projector?” I must admit, I did have to think for a minute about the best way to answer that question….


My answer after some thought, and a bit of jibber jabber was “There is not an exact answer to this in reality”


So I went on to explain…

It really depends on what you are trying to achieve when installing the projector and where you are installing it.

You see, The Keystone effect, or the Tombstone effect as it is sometimes referred to, happens when the projector is not lined up either vertically or horizontally to the screen or projection surface. When this happens, it ends up that actually, one part of the image is closer to the screen than the other, so you have a bigger image maybe at the top than at the bottom. This is because if  the projector on a tilt, it is closer (say) at the top due to the angle that you have put on the projector.



Today’s projectors are made with a keystone correction function, that allows you to adjust the image digitally, to fit the screen.  This is a very handy function for the DIY’er and also professional installation teams alike.

Its great for DIY’ers because they don’t have to worry to much about the exact location, they can get it roughly in line and away they go. For Professional installation teams, you can use a laser to line them get them perfectly set up and away you go, no keystone needed, but what happens if there is something in the way or you have an extremely high ceiling and its not the perfect world?


People that work as image calibrators or work with high resolution video with tell you that there is only one way to install a projector and that is with no keystone. And that technically is true. You see, when you Keystone a projector image, there can be a loss of image quality. This comes as a result of stretching the narrower place of the image and compressing the wider place. This is effectively altering the Native image that the projector was supposed to be displaying.


In Reality however, an installation does not always lend itself to the perfect alignment. Sure,  if you are building a theatre room, there really is not reason why you should use very much keystone, and that is an instance where you definitely would not want to, as you want to make sure you get the full HD experience when watching a Movie, FTA TV or even Gaming, but if you are in an environment that has a high ceiling or obstacles in the way, or the screen mounting location is really low amongst a myriad of other things, you may not have a choice and if you are simply showing a basic power point from a standard 1024 x768 computer, you will more than likely never see the difference.



So To Keystone or not?..... well in my opinion its horses for courses, sometimes you can and sometimes you just cant. In a Home theatre situation, maybe not, but in a School classroom, where you have to take into consideration that kids can put there arms up and hit the projector if it is installed at the proper height or it is simply sitting on a table and it has limitations of height, then a bit of keystone is absolutely needed. For us, the things we take into consideration are – Aesthetics, practicality and best practice

Food for thought!