What are the main differences between lamp and laser projection? Barco’s Tom

Five Differences from 2011 (Lamps) to 2021 (Lasers) Selecting the Right Projector for Your Screen

Tom Bert, Director of Cinema Technology, Barco

Cinema is over 100 years old and is over 20 years into its digital history. Starting officially around the turn of the century, its digital history really took off between 2009-2014. In that five

year period, a whole industry almost completely converted from analogue to digital - something to be collectively proud of. But that does mean that a large portion of the digital equipment out there is now reaching its 10-year-old operating birthday. The vast majority will be running well and will continue to do so for many years; yet many exhibitors are preparing for the next 10 years. In this article we will zoom in on selecting a new digital cinema projector and ask: what are the differences between 2011 and now? How should we make these choices? And why is this important?

1Modern Times

The first thing to take into account when selecting a digital cinema projector is the timeline you’re planning for.

In 2011, lamp projection ruled. A lamp warranty and lifetime ranged from 3000hrs (<1kW lamp) to 300hrs (>6kw lamp). Within that time frame the brightness dropped from 100% to around 50%. As an exhibitor you had to accept that periodical drop to 50% and make your choice with that in mind. Over the lifetime of the projector, you would be swapping anywhere between 15 and 150 lamps; with every lamp swap your brightness would swing up again, only to drop back down in the next weeks and months.

The timeline when selecting a laser projector, however, is of a different magnitude: we’re not talking hundreds or thousands of hours, but tens of thousands of hours. The drop to 50% is also not a given. Laser projection allows you to be more flexible in

Then and Now

The digital cinema market of 2011 was very different to how it is today. In 2011 around 64,000 screens were digitized, around 51% of the market at that time. 10 years later, 203,000 screens are now digitized; a number also known as roughly 100% of all screens. Incredibly, over 10 years the total screen count grew by more than 50,000 screens. And the talk of the town, and the topic that drove discussion back then, was “Avatar”. Released in 2009, this blockbuster is what convinced many exhibitors to adopt digital. In many cases it’s what made them adopt 3D. Another defining parameter was the infamous Virtual Print Fee (VPF): the studio financing scheme to stimulate digitization defined where, when, at what price and from whom you bought your projector. That then defined what type, brand and model of projector landed in your booth. 10 years later, the elephant in the room is COVID-19: many industries were and are still struggling; and we’re not completely out of the woods yet. A careful approach is defining many of our current actions, including the selection of a digital cinema projector.

And finally, the new technology element in the mix to consider: laser projection. Brought to market in 2014, it’s more than just a component inside the projector, it’s a driver for advanced operations, integration, automation, sustainability… hence why it will appear frequently throughout the article.

the actual use of the projector (power, ambient temperature…) and how that translates into brightness over time. When you consider 14fL as the reference 2D brightness, the list of options is endless in the case of laser: do you want to keep that 14fL over 10 years, or do you accept a slight drop to 11fL if that permits you to use a smaller model? Or do you prefer six years of 14fL, followed by another six years before reaching 7fL? Your projector manufacturer will help you plan and model out all possibilities .

2Cool Runnings

The second important difference between 2011 and 2021 is the cooling of the projector and its booth. When looking at the CFM (cubic feet per minute) specifications, laser projectors expel (and hence pull in and filter) more air than lamp projectors - about 75-80% more.

However, CFM is not a relevant metric when looking at cooling, since it doesn’t say anything about how hot that air is, or about how much it impacts the environment that it’s blown into. For that, you need to look at the BTU/h specification (British Thermal Units). The BTU/h of a lamp projector is 100-110% higher than that of a laser projector. Laser projectors transport more air, but it’s relatively cool air: you can easily hold your hand above the air exhaust of one. But a lamp projector expels very hot burn-your-hand air. A large Xenon lamp, heat-wise, comes pretty close to an open fire burning inside your projector hence why a chimney is put on top to “exhaust” that hot air out.

The law of physics then causes fresh air to flow in through available openings. But even though that air is cool, it’s dirty. So even though you’re removing the hot air, you’re actually causing harm by introducing dirt.

An exhaust is not needed in the case of a laser projector: the impact of turning the projector on is the equivalent of an additional 10-20 people walking into a building which the HVAC (Heating Ventilation Air Conditioning) system is scaled to absorb.

So if there’s one takeaway from this article, let it be: please stop “exhausting” a laser projector.

3Big Fish

The third difference is related to brightness levels that can be achieved out of the projection lens. Digital cinema lamp projectors are capped at around 35klm. This was defined by the “e10due” limits that lamps introduced. E10due is an optics/physics phenomenon that (in a nutshell) explains why one plus one is not equal to two when adding up light.

When people ask us at Barco, “Why don’t you put two lamps into your 30klm lamp projector to create a 60klm projector?”, the answer is easy. One plus one in the case of Xenon lamps equals around 1.2 - the optical limitation of adding more lamps would only be slightly higher than one lamp (and you’ll create a projector twice as big). Laser light is highly collimated, so it is less impacted by the laws of e10due - so one plus one comes pretty darn close to two. What we call the “laser light source” of a cinema projector actually contains hundreds of individual lasers (diodes) and they all add up inside with almost no efficiency loss, which makes getting beyond 35klm achievable.

The new limitation, however, is that somewhere inside the projector all that light needs to be mapped onto a pixel structure not much bigger than a postage stamp. And the device needs to be kept performant, cool and reliable.

But the cherry on top: laser light can be dimmed flexibly. Where lamps start flickering once you go below 60%, lasers can easily be dimmed to 20%. This makes life much easier when you want to achieve different fL targets for your 2D and 3D shows.

4Moneyball

We know that a laser projector costs more than the equivalent lamp projector. But there is a logical explanation for this, which we covered in “Modern Times”. When you buy a lamp projector, you buy a couple of weeks’ or months’ worth of light to go with it. Whereas a laser projector comes with a lifetime’s worth of light inside.

When digital projectors were introduced to cinemas, they were compared to 35mm projectors. At first glance from a purely financial viewpoint, continued use of a 35mm projector seemed like the most attractive option. But the VPF played its role and, looking back, all exhibitors are happy that they took the step into digital.

It’s safe to say that laser projection now stands on its own merits - and, of course, because of Total Cost of Ownership (TCO). When you compare that lifetime’s worth of light to what you are spending on new lamps, the finances always make sense. The payback period differs case by case: it might be two years, it might be up to eight years but here projector manufacturers can help model things out. And specific financing solutions also exist just for this. One thing is certain: you’ll be happy with your transition from lamp-to-laser projection.

5Austin Power(s)

In “Big Fish” we touched upon how laser projectors can achieve a higher brightness level. And, remarkably, this is done in combination with higher power efficiency levels. Quantified in lm/W (how many electrical watts directly out of the wall are needed to create the lumens out of the lens), lamp projectors land around 3-5lm/W, whereas laser projectors can reach levels of 12lm/W.

This not only makes laser a more sustainable solution; it also has an immediate and impactful effect on your electricity bill. A mid-sized lamp projector easily costs more than EUR4,000 per year, purely on running costs, which means that at the end of its lifetime you might have spent more on power than on the projector itself. A laser projector with the same brightness would cost you less than half in electricity.