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Discussion Starter · #1 ·
I have a sample at home and while I can see a slightly blacker black, at the same time the whites are slightly darker. So, since I don't think it helps improve the contrast, shouldn't I be able to replicate a Greyhawk performance by adjusting contrast and brightness? Am I missing something? I do notice that colors seem to be more saturated and seem overall cleaner...I think.

BTW I have a Sony W400Q.
 

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Luis:


I had the same question. You can read about my thinking process in this thread .


What I concluded after some education by other forum members is that there are several factors in the image improvement by GrayHawk and Da-Lite high contrast screens. The glass beads on the surface help to reject ambient, off-axis light, and to direct the reflection of on-axis light, most of which comes from the projector. The gray color further minimizes the amount of scattered light that the viewer sees. And there is probably some contribution by the human visual processing system.


As you point out, when considered versus a matte white screen, the gray color is just like turning down the brightness. And compared to a matte white screen, a beaded screen focuses most of the light at the center of each bead. The eye acts like a peak detector for these "tiny bubbles," so there is effectively, higher contrast.


But note that the projector adjustments are only part of the whole image experience. By controlling the screen performance, it is possible to extend the performance of the system as a whole.


At least that's how I now think about it.


-yogaman
 

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Just to be clear, the other thread said that the Grayhawk screen material had glass beading, and that is NOT correct.


I want to clear that up because some older screen materials did actually use glass beading to create high gain screens for use with low brightness digital projectors in high ambient light conditions like conference rooms.


But glass beaded screens are horrible for brighter projectors and home theater use.


I can understand the confusion because the Grayhawk does have translucent optical coatings on top of the gray to reduce incedent light washout, which reduces contrast and percieved black levels. But it's not glass beading at all.


Luis,


It would seem that lowering the brightness and changing the contrast levels would bring about a better picture, but it's not the same.


The projector controls can only affect certain image parameters, and increasing the contrast will just cause a harsher difference between light and dark areas completely washing out bright areas and losing shadow detail in dark areas.


And reducing the brightness will also only work up to a certain point and then again you will lose all detail in the darker areas and generally the picture will look muddy with muted colors.


This could be one of the reasons that Stewart Filmscreen is hesitant to send out fabric sample sheets because the improved effect of contrast, black level, color saturation, and added shadow detail relates more to the whole screen and may not be so apparent on a small swatch of the fabric.


The improvements of the Grayhawk are subtle, but easily visible, with different movies, and different shots showing the picture quality improvements better than others.


If you have a chance to see a Grayhawk screen setup in a A/V store nearby you would see what I mean. If you are lucky, you might find a local retailer who will let you bring in your W400 to try it out on their screen.


-Dean.
 

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You can't achieve the same black level with the brightness control that you can get with a gray screen. The black level of an LCD projector is limited by the amount of light that bleeds through the panels at full off. Turning the brightness control down will not make it any darker. A gray screen does make it darker and since the whites are too bright on most digital projectors anyway, it makes for an excellent combination.


Ken
 

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If this were true, then you could project on to a white or grey painted wall and use the contrast and brightness to make the picture as good as a screen.


Doesn't happen most of the time.


drewman
 

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Quote:
Originally posted by Ken Donowho:
You can't achieve the same black level with the brightness control that you can get with a gray screen. The black level of an LCD projector is limited by the amount of light that bleeds through the panels at full off. Turning the brightness control down will not make it any darker. A gray screen does make it darker and since the whites are too bright on most digital projectors anyway, it makes for an excellent combination.


Ken
This is it. forget fiddling round with brightnes or contrast .A gray screen deepens the black of the deepest (non) black that the projector is capable of even IF itS contrast and brightness IS set to -30 (d-ila) or any other maximal minus.lOOK AT THE BLACKS WHEN THERE IS NO SIGNAL (there is sync)and notice that the blaks are not blacks at all. This black will deepens with a gray screen even when it is a (self) painted ligt gray

k
 

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Luis,


As a fellow 400q owner for about 1.5 years, don't forget that our projector only has a maximum rated output of 400 lumens. Actually, it's really closer to only 250 lumens or so with new lamp and 120 lumens by 1000 hours of use, as measured by Bill Cushman and posted to the Big Picture 400q Forum.


As I understand it, the GreyHawk is targeted towards very high brightness projectors with closer to 800-1000 lumens. For the 400q, it has been suggested many, many times that the Dalite High Power is the way to go for improved contrast, brightness and punch. I am still using a homemade screen, as I'm in the process of building a dedicated theater in the basement. The Dalite HP screen is the way I will probably go.


Dino
 

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Dino,


I received my first Dalite High Power about two weeks ago.

I can describe it's performance with one word... WOW!!


It's done wonders for my CRT projector. I only wish I

had bought it when I had my Davis DLP.

While not very suited for use with the higher output

projectors I now would not be without it when using a

projector rated at less than about 600 ANSI.


Bob




------------------

~ The Sultan of Cheap ~
 

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Discussion Starter · #9 ·
But doesn't a high Power screen means lighter blacks? How can it improve black leve or contrast? I tried vidematted 200 and studiotek 130 and was impressed with the lghter blacks. I also noticed using the greyhawk that darker colors that weren't very visible in my DIY blackout screen are more visible with the greyhawk. For example I can better see the red (wine like) color of the horsemen's robes in Gladiator.

Maybe due to my pitch black room I don't need too much light ouput from my projector and thus I can use a greyhawk with a low lumen projector like my 400.
 

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Luis,


Apparently, the HP screen increases the contrast ratio over using a matte screen by rejecting ambient light that would otherwise wash out the picture. This screen material is special in that it reflects the light back to the source - i.e., it's retro-reflective. Plus, the increased gain supposedly raises the perceived black level by making the whites brighter.


Again, I am not speaking from experience. I have drawn these conclusions from the literally dozens of postive testimonials posted on the Big Picture 400q Forum.


Dino
 

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Bob,


Isn't the DaLite Hi Power retroreflective? Is your CRT ceiling or floor mounted? I have been thinking about higher gain screens recently.


------------------

Jeff

Currently - Zenith 7" CRT, 80x60 1.3 gain screen


Soon to be - 107x60 1.3 gain...with ?Seleco 250 with Panamorph or "cheap" 9" CRT
 

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Discussion Starter · #14 ·
"by rejecting ambient light that would otherwise wash out the picture."


But doesn't my pitch black room make that feature useless in my case? Screen selection is very hard indeed....heck, seems that anything that you want to buy for your HT means LONG nights of internet research...
 

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I was referring to ambient light that is created by reflections (from the projector's incident light) off of the screen to nearby surfaces in your room.


With a matte white screen, during scenes of high contrast, the bright areas could cause reflections off of nearby surfaces that may wash out the darker portions of the image. With the HP material, since the screen is retro-reflective, it doesn't reflect most of this unwanted light back to the viewer.


I don't think any screen material is going to give you much darker blacks without compromising the brightness that is so much needed with the low output 400q. If you don't mind the darker whites, then the GreyHawk may be the screen for you. But for me, I would rather have an image with increased brightness, more vibrant colors, and overall punch.


Don't forget, the 400q lamp is much brighter when it is brand new, and after about 200-300 hours, it's no where near as bright. I have about 350 hours on my lamp, and black level is not a problem for me anymore. How old is your lamp?


Do a search on the Big Picture 400q Forum:
http://www.thebigpicturedvd.com


You will see that for over 2 years, the Dalite HP material is the screen of choice for many 400q owners. It might be worth getting a swatch of this material and checking it out for yourself. You may like what you see.


Hope this helps.


Dino
 

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Discussion Starter · #16 ·
I tried all Dalite samples and wasn't impressed by any of them. Their grey sample was too dark for my projector and the when I tried the HP sample, there was no way that I could match the image quality I was getting with the greyhawk or my DIY blackout fabric, with the HP. The blacks were too light and adjusting the contrast and brightness only washout the image. My lamp has 500 hours. Keep in mind that my projector is top shelf mounted and that all the walls (incuding the ceiling) around the screen are coveres with black fabric that reduces reflections a lot. I've read that the blackout fabric has from 1.3 to 1.5 gain but based on the sample I have I have to say that it is closer to a .9 cause it is lightly brighter than the greyhawk and darker than the matte 1.0. Maybe there are different type of blackout fabrics... Anyway, while I do like how the Greyhawk make the colors look there difference is so small compared to my DIY that unless I can get the fabric only for a not so high price I think I'll stay with my DIY screen. From what I've heard the greyhawl is pretty expensive. One thing that makes seems hard for Dalite to compete with steward is that their sample are so small that is hard to judge them.

Regards
 

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Discussion Starter · #17 ·
My current screen size is 8' wide. The screen is a 2:1 DIY so I can adjust for different aspect ratios.
 

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Luis,


Just out of curiosity, what is your current screen size? I currently only use a 60"x34" (about 70" diagnal) homemade screen, but I will be upgrading to a 106" diagnal 16:9 screen when I finish my theater.


All things being equal (if I were to use the same screen material, which I won't), the absolute black level will be lower due to the expanded image size.


Just something to think about if you haven't already.


Dino
 

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Quote:
Originally posted by Luis Gabriel Gerena:
I have a sample at home and while I can see a slightly blacker black, at the same time the whites are slightly darker.
Luis,

A few things. Screens are linear in that lower gain screens will reflect less light evenly. In that sense it can never acutally change the contrast, that is a function of your projector. To me the advantange of low gain screens is in situations where ambient light is not controlled and you have a high output projector. In that case your perceptions of contrast may improve. In those situations less ambient light is reflected back to the viewer. This will only be a benefit if your projector has enough light output to overcome the low gain. If ambient light is well controlled then I don't see where its an advantage. In that case you want a screen with good gain that will not hot spot. If you feel that the image is too bright then you can use a neutral density filter to lower the overall output (although I would doubt that you'd want to do that with the 400Q). This is the best way to "turn down" the brightness because it won't effect the calibration for black and white levels. Some projectors have this control, typically called cinema mode, that basically lowers the light output for controled room conditions like you have. Considering your room situation, I am not surprised that you are not thrilled with the low output screen material.


BTW, I have a 400Q with a Stewart Sudiotek 130 89" wide, 1.85:1 screen. The room is well controlled for light, the walls are green and there is no external light entering. The screen is mounted in an alcove about 1 foot deep and surrounded by black fabric. I don't feel that the image is bright enough to experiment with ND filters. However a big improvement in the overall viewing experience was gained by masking the gray bars for 4x3 and 2.35:1 films. If you don't have a masking system, spend your time on this, it makes a big difference.


Regards,

John Moschella

 

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Discussion Starter · #20 ·
I do have masking for 2.35:1 since I only watch dvds and did a great difference. Regarding the screens I've been testing, I wasn't that impressed with the greyhawk but I still can see some improvement and would like to get it if not for the way to high price. The real dissapointments were the high gain screens. I wasn't able to deliver better contrasts to make the black darkers no matter what. That is indeed very dissapoiting to me since I wasn't really looking for a brighter image. Also, as I've read, the idea of HG screens is to help viewing when there is some light on the room. I understand what you said and may be is due to the extra small sample by dalite but my results has been very poor with HG screens. I wouldn't trade my Blackout screen for any of them...only for the greyhawk because it gives me a little better saturation in dark scenes and a very small contrast iprovement which may or may not be an illusion. I guess HG screens work ncely with CRTs to improve light ouput and since they have jet blacks everything is ok but with LCDs I don't see how they could help except for no light controlled rooms.
 
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