Film-Tech Forum ARCHIVE: Christie 4K contrast ratio

This is topic Christie 4K contrast ratio in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Marco Giustini (Member # 4544) on 01-28-2017, 06:45 PM:

Just noticed that Christie boast the same contrast ratio for 2K and 4K Xenon machines when 4K chips should really deliver a lower value AFAIK.

Is that just bad marketing or did they actually develop something to achieve that? I know you can increase the contrast at any time by trading light in exchange but that does not seem to be the case.
Thanks

Posted by Steve Guttag (Member # 268) on 01-28-2017, 07:38 PM:

I have not found that their actual contrast seems lower (haven't actually measured it). They also don't use a LUT-SCC file as Barco does. Heck Barco has developed it to the point where one can make their own LUT-SCC, which is pretty cool...you have to download the latest clone package to get the test patterns.

Christie does offer irises as well as High Contrast lenses too, which could improve contrast at the expense of lumen output. Barco has HC lenses too but are adamant that they are just for the P and L projectors and have not been tested on the full sized "B" projectors and could have issues handling the heat.

Posted by Alan Gouger (Member # 543) on 01-28-2017, 10:57 PM:

Christie will show their own ( non Dolby ) HC Laser at Cinemacon rumored to achieve 16000:1 native.

Posted by Marco Giustini (Member # 4544) on 01-29-2017, 05:01 AM:

the uniformity issue with a 4K chip should be part of the technology, it sounds unlikely that Christie simply don't have this problem. What happened to the PCT (Pureformity Colour Technology) which I was shown years ago and was told it was based on ICP's SCC? (I have a Christie slide that mentions that!)

So are you saying that Christie 4K engines seem to feature the same contrast of their 2K machines? I may be able to take a measurements soon, I am curious now!

Posted by Steve Guttag (Member # 268) on 01-29-2017, 12:01 PM:

My wording was VERY poor...Yes, Christie's contrast on 4K seems inferior to their 2K projectors of the same model. I have not measured it, however. I do find it odd that they do not seem to utilize a special LUT-SCC file, as Barco does for all 4K and S2K projectors. Only Barco, thus far, does that.

Posted by Marco Giustini (Member # 4544) on 01-29-2017, 02:10 PM:

Thanks Steve. I'll try and take a measurement.

I found this slide.

So Christie in the end never implemented that feature?

Posted by Carsten Kurz (Member # 5396) on 01-29-2017, 04:48 PM:

I guess, for those contrast spec figures, the manufacturer chooses a lens that will give the best possible measurement (same as they do for brightness). For a 4k machine, this is most certainly a HC lens in tele-setting. For brightness measurement, they would prefer wide angle.

I have seen some announcements for improved contrast machines, but it seems they still achieve that while loosing quite some light.

Now, after having sold their first laser machines, the DP4K-60L, at around 300.000US$ with a not-so exciting 2800:1 contrast figure, Barco now announced their LHC models with 6000:1. As someone who bought a 60L at that rate, I would be really pissed off.
But actually, I guess the actual companies/managers that bought the 60L simply do not care about contrast.

As for the SCC, I guess Christie is using it just as Barco does. Just that Barco only recently made that method available to technicians through Communicator. I mean, series II 4k is available for quite a while now, and I guess Barco and Christie for the recent years only implemented this as a factory calibration and locked it to the specific light-engine. Maybe Christie will come up with a similiar option for self calibration, or, they may not find it practical for on-site measurements.

- Carsten

Posted by Marco Giustini (Member # 4544) on 01-29-2017, 06:30 PM:

The Barco SCC calibration is just great, it takes you out of jail when some precision is required - previously you could only swap the whole engine. Are you suggesting that a Christie comes with the SCC already enabled and it's not customer-adjustable?

I am not an expert but are you suggesting that D-Cinema lenses change their brightness and contrast depending on zoom position? I cannot remember the name of the optic configuration but I thought that that was not the case with D-Cinema lenses - that is, they produce the same contrast/brightness at any setting.
Christie are advertising the same contrast for both 2K and 4K machines - even though some datasheets/pages say >2100:1 for 2K and "about 2100:1" for 4K - but not all the sources I found are consistent.

Posted by Alan Gouger (Member # 543) on 01-29-2017, 06:38 PM:

From what I know the Barco 6p Laser is available in a standard and HC version with the HC avail in only two models the 30L and 60L.
As mentioned to achieve HC you lose light, for instance 30L HC ends up a 20LHC.
The HC model includes the contrast enhancements and the new Alchemy with HDMI 2.0 with HDR support and HC 4K Lens.

You can purchase the standard 30L or 60L with standard lens and current Alchemy much cheaper which will suffice for most cinemas, the HC version is target for privet screening rooms and cinemas who would benefit from the additional contrast.
The new Alchemy ( not shipping yet ) if purchased individually not bundled with the 60/30LHC will sell at a premium.

Posted by Tom Bert (Member # 5719) on 02-07-2017, 04:11 AM:

When you look in the Christie user manual for the e.g. the CP4220, they mention "Achievable Contrast Ratio 450:1 ANSI, 1850:1 Full Frame ON/OFF". That is different than the website (https://www.christiedigital.com/emea/cinema/cinema-products/digital-cinema-projectors/christie-CP4220-DLP-Digital-Cinema-Projector) that mentions ">2,100:1 full field on/off"

It's not explicitly mentioned, but the higher contrast is probably -only- achievable with their high contrast lenses. That will have an impact on brightness, but also is not explicitly mentioned.

Posted by Alan Gouger (Member # 543) on 02-07-2017, 10:15 AM:

Adding a HC lens to a RGB laser projector can negatively impact
uniformity.