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Discussion Starter · #1 ·
 http://www.thebigpicturedvd.com/bigequipment17.shtml I've seen these pictures on the review of the PLV HT70 on TBP site a number of times over the last couple of months and just noticed something strange in one of the shots.Assuming that the blackest black your pj can deliver depends on how well lit or in this case not lit the screen is...take a look at the shot where the window closest to the screen is opened and look at jacks hair and the guy's shirt sitting next to him.Then take a look at the wall directly behind the halogen lights above the screen.Now the wall is white and the screen is grey but it's not black so how do we get that deep a black from the screen when it should be lit up from the direct light from the window?The only explination i can come up with is that the photo was put through photoshop like allot of people do here...taking a shot of the screen in the dark and pasting it in another day shot of the environment.But this is a review and i really doubt that jeff altered the shots so what gives?Anyone?
 

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... so what gives?

Don't judge the PQ of a projector from digital pictures posted on the Net.

Period. End of discussion.
 

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Discussion Starter · #3 ·
"End of discussion"maybe for you.But my question still has'nt been answered.So the question still stands.Yes i know better than to judge pj's by looking at digital pictures on the net mike thanks...and this was'nt a poke at the sacred plv 70 ht...what i was asking was really what optical effect are we seeing here.Why do the blacks seem totally unaffected by the light shinning directly on them,like the portion of the wall directly above the screen?I know that the greyhawk has ambient light rejecting qualities but is this what we are seeing or something else?
 

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What you are seeing is a digital camera at work. Digital cameras are horrible picking up low light levels. This has the effect of making dark greys look black.
 

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Period. End of discussion.

....................................


Don't pick on Canadian's. Their all smarter, wiser and better looking.


Continue the discussion leaders of the north :-( . Mush !!
 

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Jimmy, I love Canada and its Peoples :D

BTW, where have you been?


PS - My 20HD is going back to SE for the 2nd time - and Sanyo will adjust the color impurities, since they are the only ones who can do it!
 

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I poke in once in a while just to see if I can give misinformation or insult Texan's :)


Who in tech are you working with Mike ? Give me a E-mail and let me know what you've learned and what their "fixing". Also did you talk to Steve ?
 

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Dreamstate


I'm a relative newby so my answer to your very good question is based on what I'm reading from a couple of different websites.


The website you referred to states that they used a Stewart Grayhawk screen to conduct their test.


Here is another website with a writeup on the Stewart Grayhawk http://www.stewartfilm.com/home_cine...%20Theater.pdf


Evidently the screen is darker than the wall section that you are referring to, therefore the projected image reflecting off of the darker screen will appear darker than if it was on a white screen or the wall.


I think the interaction there is that they are overpowering the ambient light with a bright projector on a gray screen.
 

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It's an optical illusion, try it yourself, I just did.


Take a very small clip of the darkest part of jacks hair and paste it next to a similar clip of the wall behind the screen. If you really look closely at it Jacks hair is perhaps a 1/8 shade darker (by eye), but at a glance they are almost the same shade.
 

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I just did the suggest cut and paste in photoshop. It looks like a lot more than 1/8 shade difference.


I tried, unsuccessfully may I add, to copy and paste to this reply block the results.

How you do that??
 

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Regarding posting the pics you'll have to ask someone more knowledgeable than I. I've tried before without much success.


The 1/8 shade difference I referred too is a guesstimate at best. On my monitor they appear very close, a whoooooole lot closer in shade than they appear in the screen shot. The test demonstrates just how easily the eye-brain perception can be deceived. There's a thread out there somewhere with a great link to a site that has prepared several small avi's that demonstrate this physiological phenomena quite well.
 

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Quote:
Originally posted by bbobbo
and this particular picture, i think:
That is by far the best optical illusion I have ever seen.


Really makes you wonder how we don't fall flat on our face, doesn't it? ;)
 

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That illusion is so good that, when I first saw it, I decided I had to verify it---so I opened up the image with a paint program, cut a patch from square A, and dragged it over to square B. It was eerie to see it blend in perfectly. I recommend the exercise.
 

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And this is why I continually advocate backlighting screens in a digital projector environment.... For CRT's this would be useless but for lamp projectors that will never attain that last tiny part of the finite 'blackness' that the CRT folks always tell us is what we are missing we can simply fool our optics into seeing what is not there....


The art is getting just a tiny tiny light leakage from directly behind the screen to illuminate the wall (not allowing any light to bounce forward into the room directly only the rear wall) and again emphasis on the tiny amount of light needed... Like a lumen or two... Try this and then calibrate your projector so you have the full greyscale and it makes blacks look, well black !!!! :) !! The higher the CR of the projector you are using the less backlight to give it...
 

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Wow,thanks for the link bbobbo.I wouldn't have believed it if I didn't see it for myself.Time for some backlighting.
 

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Yes, thats the site. Its startling how different things can look from a different perspective. I agree that backlighting will probably help the percieved black levels as well. I plan to do it myself someday.
 

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The emperor has no clothes!!! I don't buy it. They are NOT the same shade of gray on my 15" LCD Dell monitor. I covered the entire screen with the exception of the two squares and the difference was readily obvious. Maybe when this graphic was first put together on whomever's monitor, they were the same... But they sure aren't on my monitor. Try it for yourselves.
 
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