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Discussion Starter · #1 ·
I wonder if anyone could answer this question.


I like to keep up to date with technology and was looking at the recent Sony and Christie digital cinema projectors which state something like 18,000 lumens and 2000:1 contrast ratio and this got me wondering about some things in relation to the home market.


Now obviously more lumens are needed for very large cinema screens but i was wondering about the contrast ratio of cinema projectors.

Why for example is the latest Sim rated at 30,000:1 contrast ratio yet cinema projectors can only manage 2000:1 ?

Are the black levels of cinema projectors as good as the best home projectors or is there a compromise ?

Is it the case that the more lumens there are the less contrast is needed ?


I notice at Cine4home they have a cinema projector and i was wondering how do they play Blu Ray discs on that because there is no HDMI input ?


Here's a good example of one of the digital cinema projectors i am talking about.

http://pro.sony.com/bbsc/ssr/cat-pro...oduct-SRXR220/



If you bought a digital cinema projector for your home could you own the actual same film they show in the cinema or are you restricted to Blu Ray only ? Obviously that would be a very expensive market but i was wondering.


I find it interesting to read news on the latest digital cinema projectors so if anyone knows good sites then please let me know.
 

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Quote:
Originally Posted by FoxyMulder /forum/post/15543679


Why for example is the latest Sim rated at 30,000:1 contrast ratio yet cinema projectors can only manage 2000:1 ?

Many reasons for this: 1) Most d-cinema projectors are based on designs that are several years old, while the latest Sim2 is ground breaking. 2) There is a lot of ambient light in most theaters so high contrast is a waste because the ambient light will wash it out. With ambient light what is needed is more lumens rather than contrast (to a point). 3) Achieving very high brightness is difficult to control and usually results in reduced contrast.

Quote:
Are the black levels of cinema projectors as good as the best home projectors or is there a compromise ?

Even with the projector turned off the black level will not be good in a theater because of ambient light.

Quote:
I notice at Cine4home they have a cinema projector and i was wondering how do they play Blu Ray discs on that because there is no HDMI input ?

When you get into this price range there are many options for higher quality source material than Blu Ray. If a person really wants to go the BD route and HDMI is unavailable there is usually HD-SDI (another digital interface standard that can be mod'ed into many players) and sometimes DVI.

Quote:
Here's a good example of one of the digital cinema projectors i am talking about.

http://pro.sony.com/bbsc/ssr/cat-pro...oduct-SRXR220/

Yes note the HD-SDI and DVI input specification. HDMI to DVI cables are readily available.

Quote:
If you bought a digital cinema projector for your home could you own the actual same film they show in the cinema or are you restricted to Blu Ray only ? Obviously that would be a very expensive market but i was wondering.


I find it interesting to read news on the latest digital cinema projectors so if anyone knows good sites then please let me know.

Are you interested in buying a digital cinema projector? If so give me a call



Seriously though, there is a sub-forum here on AVS devoted to d-cinema which has some descriptions of some amazing setups. You may want to read up on the interesting posts there:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=185


Most electronic forms of movies for d-cinema come in the form of an encrypted box with a hard drive and are heavily copy protected. As with anything if the price is right you could probably buy a copy from the studio, but normally I think they are rented out and carefully controlled (not your typical Netflix setup
).
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by Mark Petersen /forum/post/15550083





Even with the projector turned off the black level will not be good in a theater because of ambient light.

Lets say you had your own custom cinema built and could control the ambient light and basically have total darkness would the black levels be as good ?


I'll take a look in that other thread....Thanks.
 

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Quote:
Originally Posted by FoxyMulder /forum/post/15550508


Lets say you had your own custom cinema built and could control the ambient light and basically have total darkness would the black levels be as good ?


I'll take a look in that other thread....Thanks.

As Mark said, there is a ton of info on the other forum. There are a number of people there with experience and expertise regarding these machines.


Just to clarify a point touched on above........Your chances of obtaining DCI content are absolutely ZERO, no matter what you are willing to pay. That also reduces their attractiveness.


DCI machines offer some great facilities. some of that is actually dependent on having the content. There are other performance areas where a DCI machine is vastly superior to the type of machine native to this section of AVS. A number of the metrics are well outside the normal J6P lexicon.


Regarding black levels, its simple arithmetic. A DCI machine cant give the same black floor. A high lumen number and a low CR number simply cant do it.


PS. I wouldn't use those Sony units as an example of DCI performance. They have some very serious issues, see the other forum, and are frequently given away for free. There's a cinema near me that had 16 supplied and installed, including full support, free. The Christie and Barco units are superior performers.


They're not for everyone, myself included.


There are, however, machines being offered from a number of companies that go some way to combining the advantages of DCI machines and consumer units.
 

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 http://www.dcimovies.com/DCIDigitalC...emSpecv1_2.pdf


The DCI standards state "it is critical that Mastering Projectors have an equal or higher sequential contrast than all exhibition projectors". That mastering projector is nominal 2000:1 minimum sequential, 150:1 minimum intra-scene checkerboard contrast.


DCI has a different color gamut, grey scale color and gamma curve to home formats. They are also three chip DLP and usually use Xenon lamps.


I believe gamma determines what contrast is displayed in the image, and image brightness how sensitive the viewers eyes are to that contrast.


The DCI standards are very low compared to home cinema projector specs.


White level nominal 48 cd/m2 (14fL), tolerances review room +/-2.4cd/m2 (+/-0.7fL), theatrical +/-10.2 cd/m2 (+/-3fL)

Luminance uniformity, corners and sides, nominal 85% of center, tolerances review room 80-90% of center, theatrical 70-90% of center


So as low as 11fL center of the screen, 7.7ftL corners and sides and still within spec. Some cinemas apparently fail to even meet this as they save money by not replacing their lamps as often as they should. A home cinema can easily do better.


Sequential contrast nominal 2000:1 minimum, tolerances review room 1500:1 minimum, theatrical 1200:1 minimum

Intra-frame checkerboard contrast nominal 150:1 minimum, tolerances review room 100:1 minimum, theatrical 100:1 minimum


So as low as 1200:1 sequential, 100:1 intra-frame checkerboard. A dedicated bat-cave home cinema can do better.


Ambient lighting, with projector turned off, screen luminance should be less than 0.01 cd/m2 (0.0029ft-L) for mastering, less than 0.03 cd/m2 (0.01 ft-L) encouraged for theatrical but maybe higher due to safety regulations, although this will lower contrast.


No health and safety regulations at home to undermine the picture quality.


Gamma 2.6 (down to 5% peak white, then "nature`s tone mapping" used to provide a gentle or steeper curve to match the displays black level), tolerances per component review room +/-2%, theatrical +/-5%


Sadly the better gamma curve, bigger color gamut, different grey scale color, 12-bit encoding, etc... are all down to the format. Home formats are mastered for living room TVs not bat-cave projectors.


I expect the reason projectors need so much contrast is down to the relatively dim white level compared to a sunny day and the dark surround effect, both reducing viewer perceived contrast, requiring gamma and contrast to be increased. Actual contrast going by photography does not seem very high. http://www.rogerandfrances.com/subsc...s%20range.html
 
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