HDTV Forum

ISF Calibration

Did you know that Video is a system with standards? For our old analog we call it NTSC and for HDTV it is called ATSC. The reason for standards is so we can reproduce the original signal with integrity along the chain of devices so that when it finally ends up on your screen you have the same image that we started with at the studio or from the master. To make this happen all the components in the chain need to be calibrated to a specific standard. This includes your display better know as a television set or the TV. It seems simple and you do see pictures but are they being displayed properly? Are you seeing the correct colors? Can it fully resolve the resolution of the system? The first problem comes from marketing and selling the display. If you walked into a show room and saw every display not only showing the same image but also appearing to look the same what would you buy? In fact your purchasing decision would be much more difficult unless you understood what is required to display the image accurately and what an accurate image even looks like. It is quite possible that brand awareness would diminish since they all appear to look the same anyway and price would become the key decision for most folks. Due to this all TV

Why would anyone prefer artifacts?

People buy them everyday. An artifact is anything in your picture that doesn't
belong. In this sense artifacts always degrade picture quality and is seen as
a negative. but...

Hypothetically, you are sitting in an airplane hanger with an HDTV camera
pointed outside at a scene and this goes through equiment and stuff until it
is finally expressed on the screen and received by your eyes. With a Kell
factor of 1.0, a perfect picture, you are unable to make out any difference
between the scene itself and the scene being displayed. I now add another
display with exactly the same response. I remove your ability to see the
scene, your reference point, and I start manipulating only one of the displays
leaving the other alone throughout the process. I tell you to come back in an
hour. Lets say I add a little color and introduce edge enhancement. You
return, look at the picture, and feel that the picture looks better than it
does on the other display. I tell you to come back in another hour. Now I
insert SVM and change the color timing. You come back and say the picture
looks even better. I ask you which display is accurate and you choose the
manipulated one. Now I let you compare both displays to the actual scene. You
suddenly realize that the picture you thought was great really doesn't look
exactly like the scene. You see that what you thought made the picture better
was actually removing picture information.

When the display is capable of full resolution of the source my job is
straight forward - remove all artifacts.

Now lets take the above hypothetical and change the displays out for HDTV RPTV
as an example and go through the whole process again. Now we have a situation
where even though all artifacts are removed it will not look like the scene.
We may actually find in this situation that introducing some artifacts will
make it look more like the scene.

When the display is not capable of full resolution of the source I become an
artist and my job is now more difficult because I want to try and get your
display to look like something it can't really do anyway.

An HDTV RPTV exceeds the requirements for 480P and performs best when all
artifacts are removed. It doesn't meet 1080I resolution though so with a 1080I
source it could be argued that some artifacts might be a plus.


So artifacts are like adding 7-Up to your wine or sugar to your coffee. People
do it all the time but you will not get the real taste of the coffee or wine
and forget about making any valid comparisons. Manufacturers have been adding
sugar and 7-Up for decades. That is why all displays that are reviewed are
calibrated. What they don't tell you is if you buy the TV and do not have it
calibrated you will not have the same picture that they reviewed and based on
artifacts - more than likely worse results. This is a problem any display
shopper will face because you can't remove all the artifacts yourself in the
store - that requires a calibrator. TV A looks better than TV B out of the box
but TV B looks better than TV A after calibration. In the end the customer
will buy the TV that has the kind of artifacts that they prefer. They will
tell themselves it had the best picture even though they never really had a
reference to begin with.

The Value of Calibration

A common view from many considering this service is that the expense of calibration is a very high percentage of cost compared to the price or value of the display with many seeing this as an issue of whether or not the service is cost effective. The purpose of calibration has little to do with price and everything to do with seeking accurate performance. Using a CRT based RPTV as an example the ISF recommends $275 for one scan rate plus $125 per additional scan rate. To a large degree the price remains the same whether the display was $1000 or $10,000. That is how much it costs to get a calibrator in your home with the necessary equipment, experience and talent to do the job.

It is recommended you get the display calibrated when it is new. Your first calibration will cover many areas that will not have to be touched ever again and is why the first one can be expensive. To get the display to this initial level of accuracy can run anywhere from about $225 to as much $1000 depending on your display and how far you wish to go.

Once that has been completed then all you have left for the life span of the product is maintenance. For RPTV displays you have an optical system that needs to be cleaned every 1-2 years. Lamp based displays, LCD, DLP, DiLA, and LCoS may have filters that need cleaning and also the lamp will change it