The recent influx of 3D technologies brought along with it a wealth of new and exciting possibilities for home cinemas.

However, this hatched several problems for installers, including having to learn a whole new method of calibration that is still widely misunderstood.

In theory, calibrating a home cinema for 3D shouldn’t be too different to 2D techniques, however, as soon as 3D glasses are thrown into the equation, it suddenly becomes a complicated matter.

This is because with 3D, there is a significant amount of light loss due to the nature of active shutter glasses. So effective calibration has to take place looking through the glasses.

Calibration expert Joe Kane has decades of experience in the industry and his name is synonymous with video quality. The brains behind A Video Standard, Video Essentials and Digital Video Essentials, if there is one person who knows how to get the perfect picture on screen, Joe does.

He says, “Often there is no simple way of compensating for that light loss without destroying the picture. You can’t turn the contrast control up because then you will clip the upper end of the picture and you will lose the detail and bright aspects of the image.

“With LCD screens, you could potentially increase the brightness of the LED backlight, however a large proportion of 3D sets don’t have separate backlight calibration for 3D. So when you choose a screen you should make sure that the backlight has separate memory for 3D, so when you toggle between 2D and 3D, the backlight changes accordingly.”

Along with the issue of inherent light loss, both active or polarised passive (or anaglyph) 3D glasses can also create a shift in colouration. And because active 3D glasses rely on liquid-crystal shutter elements, they vary in transmission efficiency and colour transparency based on the quality of the materials employed.

SpectraCal produces professional software for calibration and its Basics for Calibrating HDTV 3D Mode states that for active 3D viewing, the display should operate at a minimum of 120Hz, alternating between right and left eye, to eliminate any perception of flicker. This means that for 1/120th of a second, the left eye will be dark and the right eye will be ‘on’ and for 1/120th of a second, the left eye will be ‘on’ and the right eye will be dark. This shuttering creates the high-quality 3D effect: During every 1/60th of a second, both the left eye and right eye will be presented with two distinctly different images, separated by a very brief ‘dark time’.

This alternating presentation of left eye and right eye content is another big factor that impacts the brightness of 3D imagery. Specifically, 50% of the time, your right or left eye will be viewing a dark field, thus reducing the effective light output by about 50%. In addition, active 3D glasses are only 80-90% efficient in their transmission of light. This leaves a 10-20% of light being lost to the viewer.

And it isn’t just the relationship between the glasses and the viewer that alters our experience – every brand of glasses is unique so this can create a further obstacle.

“There are subtle differences between brands of shutter glasses and the colour that penetrates the glasses will be different,” Joe says. 

“In theory, they should be neutral and should pass all colours equally, but that’s just not the case.

“Some brands in particular tend to attenuate the blue, so you will have to push the blue in calibration in order to get the optimal colour.”

Joe notes that one of the most important things to remember is that once you have a brand of glasses you are happy with, you need to use them to calibrate, and then continue with the same brand for viewing to maintain consistency.

With so much of our viewing experience relying on the quality of calibration, it is surprising that there are still members of the industry that don’t warrant calibration as a necessity.

“There are a lot of places that will tell you that you shouldn’t bother with calibration and that it’s not worth the money. I am of the firm belief that calibration allows you to see the images as they were intended to be seen. If you want to see the exact story that was meant to be conveyed, then display device calibration is absolutely critical,” Joe says.

“Our TV is basically a form of communication system and if our languages are different, the communication breaks down.

“There is a strict set of rules for creating and displaying content. That set of rules defines how the display should be calibrated.”

Joe says that you should think of your display device as a canvas on which an artist creates what they desire within the limitations of that canvas.

“If you want to get the same artistic intent in your home, what you use at home has to match the display device that was used to create the content.

“If it varies in any form from the way the display device was set up to check the original film, then something will be lost in the translation.”

Joe adds that in Hollywood, it is not unusual for the producers to take 80 hours to transfer a two hour film to video. So without proper display calibration, much of that time and hard work is rendered invalid.

In order to get to this stage, you need to be sure that you choose the correct display device in the first place.

Although there is a plethora of 3D content available, and is constantly growing, the display will still need to play a significant amount of 2D material, so having multiple memory locations for calibration is imperative.

Most HDTVs are capable of retaining dual calibration presets for colour temperature, light output and basic settings, if you select a HDTV with ISF day and night modes or other discrete memory locations you can store calibration settings for both 3D and 3D in their own memories.

However, Joe believes that the technology still isn’t quite up to scratch.

“A display should have completely independent calibration controls for 3D as well as 2D. Most display devices do, but in many cases, the calibration capabilities that they provide aren’t comprehensive enough to do a good job and you may find yourself having to make compromises,” he says.

Joe says that these shortcomings with 3D displays are common because the sudden boom of the technology meant that manufacturers had to rush to supply the demand. The industry saw 3D as a way of getting people to purchase – whether that meant higher cinema prices or a new display device to be able to watch 3D at home. The technology exploded too fast for manufacturers to have the time to properly figure out what they were doing. Because of this, they are essentially still playing catch-up.

“We moved to 3D much faster than expected and people didn’t have the time to realise how to maximise its potential.

“The first sets on the market only had to create a ‘wow’ factor because the technology was still new. Now that has worn off, the demand is now for better quality 3D.

“Consumers are still viewing in 2D the majority of the time, so when they flip over to 3D, they realise that the quality and the contrast isn’t as good. They will begin to question why they spent the money on 3D in the first place.”

From a manufacturing standpoint, companies need to raise the bar to ensure that there isn’t a backlash from the consumer world. Joe says that people are already beginning to migrate back to 2D movies because they are recognising the inferior picture quality.

“Some manufacturers provide products that have an excellent ability to effectively calibrate, but they find that the amount of time that it takes to calibrate on the manufacturing line isn’t included in their profit margin – it’s left up to somebody else to realise that all the tools are there to do a really good job of calibration.

“So if you want good quality picture, then after-purchase calibration is much more critical than manufacturers would like to admit.”