Points of View: Considering the Projector, Screen, and the Room
CONSIDERATIONS WHEN PIECING TOGETHER A PROJECTOR AND SCREEN COMBINATION IN YOUR HOME THEATRE
After returning from some recent front projection calibrations, I thought I'd provide some dos and don'ts when selecting a projector and screen combination. Future projector owners may want to consider these important details to achieve a good picture.
Movie lovers all dream of owning a large screen converting our living room into a theatre when the lights dim. The key question is "how big can we go?"
There are several factors that are at play here, in no particular order...
1. minimum/maximum viewing distances from the screen
2. resolution of projector/source material
3. maximum light output from projector after calibration
4. screen surface selection
5. room environment
6. budget
All of the above need to be taken into account to enjoy a good picture.
Too often I get calls to calibrate a video projection system where the client made the attempt to piece it together himself or who received some bad advice from a misinformed salesperson.
Mistake #1: Going too big for the selected projector
...we all want to go big...but we need to consider capable light output here and most "affordable" projectors aren't capable of a lot of light output (aka brightness). Why is light output important? It helps with image dynamic range with is the #1 priority for good video. It makes the difference between dark blacks and bright whites. It gives the sense of a 3-D image vs. a flat, dull image. It helps achieve linear grayscale performance.
The bigger the screen selected, the larger the surface area the projector needs to fill. Make the screen bigger = making the picture dimmer. Budget projectors from Panasonic, Epson, Sanyo, Sharp, and Sony all look great on 82" screens and cap out at 92". Go bigger than that and you'll get a big picture but one with less dynamic range. So are you willing to be flexible with your budget to get the great picture you've always dreamed of?
How do we solve this?
#1 Invest in a projector capable of more light output ($5000+ projectors)
#2 Higher gain screen surfaces (but these add more problems such as sparkles and reduced off-angle brightness just like old RPTV screens)
Mistake #2: Sitting too close to the screen
So you took the advice above and decided on an 82" for a nice bright picture. You decided to sit 8 feet from it to get the widest viewing arc allowed. Personal preference maybe, but...
Pixels: you may get the immersive experience you are hoping for in home theater, but sitting this close will allow your eye to see all of those 1080x1920 pixels that make up the picture. The goal is to see a fluid image, not the pixels that make up the picture. Sitting further back, at about 11 feet, your eye will see the pixels blended together making a good image. The problem is further created by 720p projectors (need to sit further away) and LCD technology (have wider pixel gaps where dark spaces are noticed between pixels. LCoS has the smallest gaps.)
Source Material: 1920x1080p is best for this formula. If you watch a lot of SD DVD, SD television, or HD broadcast, you will want to sit further back. There are many artefacts in the video signal with these lower resolution sources. Sitting further away from these images will make them less noticable unless you are willing to compromise SD viewing for maximizing HD viewing.
Mistake #3: Poor/Misinformed Screen Surface Choice
-Paint the wall with goo or a formula some guy posted on a forum (cheap)
-They threw it in with the projector (even cheaper)
-I didn't want to spend a lot
-Screens don't make a difference.
-The sales guy told me it was the best.
These are some of the comments I've heard from end users. Screens and projectors are two piece systems to create and image and both should be treated with the same care during the selection process based on the criteria set at the beginning of this thread. The problem is that once the screen has been installed and there was a misinformed choice, the results are not as good as they could have been. There are specific purposes for screen coatings:
1. they are usually environment specific. Using Firehawk from Stewart filmscreen in a dark room is NOT recommended. If you want to alter all of your colours and grays to a dim silver shine because the dealer told you so, then be my guest. This is a screen for a compromised environment: when light in the room cannot be controlled. On the flipside, the Stewart StudioTek 100 and the Da-Lite JKP Affinity .9 are designed for completely black environments and are not recommended for rooms painted anything other than black.
2. they can compensate for drawbacks of particular projectors. The early days of digital projectors were flooded with devices that were far too bright and absolutely terrible black levels and grayscale tracking. Screen coatings were designed to deal with this and make a compromise that was acceptable but could never correct the initial problems. These materials are still available today and some salespeople are too used to selling these materials by default. Just because they applied in the past it doesn't mean they apply today!! Modern digital projectors don't need these screen coatings. Beware!
How do we solve this? Purchasing a screen from a dealer who has been educated by the manufacturer on screen types is your best bet. Stewart Filmscreen offers this training but I'm unaware if any other company does. For dim/dark rooms with bright walls, a screen such as the Stewart StudioTek 130 has been the choice "screen with gain" over the years for its reference colour reproduction. While I like the offerings of Da-Lite, I have found that their coatings aren't always applied evenly that result in slight bright blotches on the screen.
Mistake #4: The Image is not Calibrated
If putting together a projection system wasn't customized enough for your room, not having the projector calibrated to the screen, the viewing environment, and the rest of the video components in the system will introduce a whole new series of video artefacts. Since we are dealing with big screen sizes, we are also enlarging video artefacts that aren't supposed to be there in the signal! It can make the image look too harsh, digital, noisy, and unnatural.
Setting the projector to achieve its maximum dynamic range without losing essential shadow detail and clipping whites is critical. This will determine the ballpark maximum light output in footlamberts (fL). The digital projection standard is 14fL. Adjusting grayscale will change this as pulling blue out of white will lower the fL value. Balancing the grayscale and contrast/brightness controls for maximum performance is a technique that not all calibrators have mastered if they just follow the "routine steps" of calibration. Finding a well experienced and qualified video systems calibrator is just as important as selecting the right screen and projector.
What else is involved? Turning off all video-destroying circuits, setting gamma (rise out of black), and CMS (Colour Management Systems) are things that a good calibrator will take the time and care to set correctly with the correct measuring instruments. Typical projection calibration is about 5hrs. No do-it-yourself setup can go beyond setting up sharpness, a black and white level not relative to grayscale and setup, and colour and tint only through a blue filter (which isn't accurate at all.) This is only a minor part of of the calibration process and will not achieve an image representing the signal on the blu-ray disc, DVD, or television signal coming through (all of which need to be calibrated to the display as well). The goal here is to make your projection image follow the television standards identical to the monitors in the video mastering facilities. Why? Because film and video are two entirely different mediums that capture/display different information.
At home we live in a world of video. Every single film is recoloured for home video because colours captured on film are different than colours captured/reproduced on video. Filmmakers know this therefore every single film needs to be recoloured for home video release or else it will look wrong. New colour choices need to be made. These are made on calibrated monitors so filmmakers can accurately see the changes. Everyone needs to see the same picture on their end from one room to the other. This is then put on a Blu-ray disc for you to see at home on a calibrated display that follows the same rules. Video is moving art. Would you paint the Mona Lisa red?
Mistake #5: Room Environment/Design not Considered
The walls are light beige or salmon.
The ceiling is white.
The floor has reflective tile.
The image is projected on the screen, then the walls and the ceiling are lit up from that bright screen image. That bright reflection is then sent back to the screen the same way as I were to open up curtains and allow sunlight to shine onto the screen.
Now the image is washed out. Black level is raised and no longer deep. Dynamic range is destroyed.
These are typical room design errors if video fidelity is important. I've seen screens mounted just inches away from the ceiling where light scatter is brutal. If I display a high Average Picture Level (APL) PLUGE pattern, the white part of the test pattern bounces off the ceiling back to the screen and turns the black part of the test pattern into light gray. How does this relate to real video? Any bright part of the picture will completely wash out any dark part of the image. Dynamic range is destroyed.
How do we solve this? Choose to paint surroundings dark neutral grays with no colour added (as colour from walls will affect the way we see colour on the screen far more than you may think). Black is best, especially on that white ceiling where the screen is and a few feet out, plus around the projector lens. Maximize the absorption of stray light from the screen and projector lens. Don't let it bounce back to the screen and then back to your eye. Our eye is very sensitive to this so give your eye what it wants to see.
If you stick to most of these rules, you can get a satisfying image that will be much better than you ever dreamed of. Are you designing a dedicated room and are not willing to compromise on image quality? Stick to all of these rules and be prepared for your jaw to drop and show all of your friends. Deep blacks, bright whites, Rec.709 accurate colours, and the best picture you dreamed of can be yours just by sticking to the rules.
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