Importance of "Screen Gain" for projection image quality?

[sagrada737]

Hi Folks,

It occurs to me in watching the various Home Cockpit videos - some with LED TVs and others with Projection displays.  In the videos shown, the camera lighting most always shows a fairly bright "outside view" for both types of displays.  The main differences previously noted are image brightness and contrast, and detail.  In most cases in viewing these videos, it seems that always, the cockpit environment is darkened to serve the brightness limitations of the projection mode.  This has caused me to think of one of the most important system considerations of a projection display setup for the outside display - and that is the Screen.

It seems that most folks are simply painting a reflective "screen paint", while others are using a type of screen material, and stretching it in some fashion in order to get a wrap-around image.  One thing I think is valid for our major system decisions for our Home Cockpit, is that they usually involve a lot of work and expense.  After which, we hang on to our approach, even if it doesn't totally satisfy the requirement we hoped for.  In other words, we find ourselves "stuck" with an approach and it is realistically hard to toss out our hard work and expense and casually replace it with something new.  That, in various forms I consider, is what is taking place with some of these nicely constructed Home Cockpit display systems.

This has caused me to think about what the limitations are for a Sim projection display system.  The major one of which I think is the Screen component of the display.  The saying, "You can put lipstick on and pig, and it's still a pig." holds true for many things, but as applied to a curved screen Projection System solution, the Screen seems to be a critical part of the total system.  Whereby, if you have a poor quality screen, then it does not matter how well your warping software works, or how great the resolution or lumen spec on your projectors are, or how good the video cards are, etc. - it can still end up producing sub-standard display results.  Perhaps the specifications and integration of the display screen has something to do with this?

I have not heard anyone speak of screen materials with respect to "Screen Gain", and the need for system integration and balance with respect to a specific type of projector and projection environment, eg. curved screen, ambient lighting, etc.

With projection screen material costing from $5/sq.ft. to hundreds of dollars per sq.ft., and Gain specs all over the map, I wonder what is the best screen approach for our Sim when considering a curved projection display approach?

I applaud Scott's new 5-monitor LED TV approach, and I am strongly leaning that way too (3-monitors), as it seems utterly simple for my TH2G setup.  But something inside me desires to better understand the major obstacles for projection displays in a flight simulator requirement - and I wonder if a major factor in all this has to do with the screen quality, and important issues like screen gain for the projection setup.

Any constructive comments on this are appreciated.

Mike

[XOrionFE]

My .02 is that it wont matter alot.   In the end you still have bloated pixels and low contrast ratios along with all the complexities and costs associated with warping software, alignment, etc.     I think your comment about lipstick on pig applies to projection setups in general  (LOL I know that comment is going to garner some hate mail!   ).   But seriously, please use your own judgement.  I have used mine and have been lucky enough to have worked in both environements and as posted in so many other threads, there are pluses and minuses of both systems.    I just dont see screen gain as the bigger issue with projection.

Again, only my .02.  Please dont hit me over the head with a brick

Scott

[Flying_Fox]

Hi Mike,

From my experience the expensive hi-gain screens (materials) will not provide that big of impact on 180+ wraparound system. They are better used in home theater projection systems with flat screen.They increase contrast, but from what I seen in demonstration rooms the contrast increase is not more than within 15-20%.

This is IMHO only.

In wraparound system the ambient light, reflecting from opposite parts of the screen (and  walls/ceiling) and washing out the picture provides more impact on image contrast than hi-gain screen. To me it's more important to darken the whole room with paint or black material, than sink $$$ for hi-gain screen. I completely masked the ceiling and walls with cheap black landscape fabric from Home Depot.

I have Home theater with the projector in another room and painted that 120" screen on the wall with Silverscreen paint from Home Depot. After some comparison tests on both screens I did not bother to paint the sim screen and left it white as 4 x 8 ' hardboard sheets naturally are.

Nick

[jskibo]

In my home theater I use a 1.0 gain screen. From seeing some higher gain screens I notice hot spots in the screen from the high reflectivity, an almost crystal like additive to the surface.

Sme folks use a grey screen to help with the contrast, but my room is completely lights controlled and the Panasonic AE4000 puts up a nice image

[sagrada737]

These are some interesting comments...

We often think that "more" is better, and I too once thought that screen gain was the same.  That is, the higher the screen gain, the better the image quality.  From what I have discerned from screen specs, each and every screen material and usage has "ideal properties" for what it is intended to serve.  The "Standard" for screen gain is 1.0 - that is, its baseline.  Higher screen gain in certain display applications might be required for optimum results, but in others, eg. tight radius, curved screens, it is not preferred as it tends toward "hot spots".  Highly polarized screens, where micro-lens type of technology is used serves another purpose to enhance direct viewing, but at the expense of blocking out angular viewing.

The use of lower screen gain ( 0.7 or so)seems like the best compromise for a small radius (6 feet or so) for our curved screen Sim displays.  This is because it affords wide viewing angles and is less sensitive to brightness and color contrast issues.  The down side is that this level of screen gain likewise requires a balanced selection of Projector that can support the brightness level and detail from the display requirement.

In reality, it seems that it is indeed a compromise, that for our Sims (being of hobby nature), we migrate to affordable solutions for our home cockpits - the price point which perhaps is in the lest than $10K range for the entire system (projection or TV displays).  That said, this kind of budget imposes a limit on the quality of some or all of the components of a projection display solution.  As has been previously commented by those who have seen "professional" simulator display systems at Trade Shows, some of these projection displays are simply amazing.  Why is it that we can't get the same results from our $10K budget?  I'm guessing that it the same old story, that "you can't get there from here" realization.  Where the relatively low budget simply will not allow for high-end quality from low-end equipment as applied to the problem.  Which is our case is an "immersive" outside display effect for our Sims.

Perhaps the question is best asked, "For a curved screen projection display system, what can one expect from a $10K budget?  And a related question, "What are the best specs for such a projection system?

Mike

[jackpilot]

In the videos shown, the camera lighting most always shows a fairly bright "outside view" for both types of displays.  The main differences previously noted are image brightness and contrast, and detail.  In most cases in viewing these videos, it seems that always, the cockpit environment is darkened to serve the brightness limitations of the projection mode.

The videos never do justice to the real "ambiance" as cameras usually adjust  to the brightest part of the image, basically impossible to get the kind of balance the human eye can perceive.
Hence the dark cockpit impression.
IMHO high $$ in screen material is a waste for the differential.

[Maurice]

In the videos shown, the camera lighting most always shows a fairly bright "outside view" for both types of displays.  The main differences previously noted are image brightness and contrast, and detail.  In most cases in viewing these videos, it seems that always, the cockpit environment is darkened to serve the brightness limitations of the projection mode.

The videos never do justice to the real "ambiance" as cameras usually adjust  to the brightest part of the image, basically impossible to get the kind of balance the human eye can perceive.
Hence the dark cockpit impression.
IMHO high $$ in screen material is a waste for the differential.

Totally agree.

Maurice

[Nat Crea]

Yep....been there....tried  all sorts of fancy surface paints.
In the end, Matt white is all you need...as you see from the
prehistoric projector faithful

Nat

[nicd]

I saw a pig with lipstick the other day .. it had bezels too  haha 

But seriously .. I've also tried a number of these approaches and if I was front projecting now I would go back to plain matt white. From reading around on other sites (non sim) it all seems to be swinging away from greys and silver-based paints.

I tried the 'black-widow' (grey-based, silver tint) paint for front-projection on walls a few years back and was expecting a gain of around 1.2.  Never really saw that much gain, hardly any really. The contrast and blacks were a bit better, and night scenes very good, but that's about it.

Have also recently compared back and front projection onto similar quality screen materials and found back projection to have a higher gain and contrast - given the same projector/scene.

I'm very impressed with the back-projection material from Carl's Place. It has very good brightness, contrast, solid blacks and good night performance. Not sure what the actual gain is, but it is definitely there.