AVS Forum banner

Status
Not open for further replies.
1 - 10 of 10 Posts

·
Banned
Joined
·
66 Posts
Discussion Starter · #1 ·
I'm considering D-ILA or LCOS projectors for a 16:9 screen so I will set the projector to 16:9 mode.


Is the light output a 4:3 square or a 16:9 square? ie is their light from the projector above and below a 16:9 image?
 

·
Registered
Joined
·
779 Posts
To answer your question


A 4:3 rectangle (A squares sides are all the same length)


Yes there is light above and below the 16:9 image.


4:3 projectors are just like 4:3 direct view TVs. Digital projectors are fixed resolution devices so when you go into 16:9 you are just not using block of pixels on the top and bottom. Now no digital projector has black blacks so the letterbox will be a dark dark gray so if you go with a 16:9 screen you might consider some frame masking solutions so you don't get reflections off of the frame. You could use a lens like the Panamorph or ISCO to compress the 4:3 into a 16:9 picture. This would allow you to use the entire 4:3 panel and not have to deal with letter boxes but you would need to work out the scaling issues. I don't use a 4:3 projector, mine is 16:9 so it is a non issue for me. I didn't want to deal with 4:3 issues when I knew I was going to primarily be watching 16:9 content, OTOH lots of people have 4:3 projectors and love them.


Good luck,


B
 

·
Registered
Joined
·
4,720 Posts
Quote:
Originally posted by Robert Joe
I'm considering D-ILA or LCOS projectors for a 16:9 screen so I will set the projector to 16:9 mode.


Is the light output a 4:3 square or a 16:9 square? ie is their light from the projector above and below a 16:9 image?
Robert,


Actually neither the 4:3 nor the 16:9 aspect ratios are "squares".


The rated light output from the projector is for the full panel. If you have a 1500 lumen G15, it will output

1500 lumens of 4:3 image, but only about 1125 lumens of 16:9 image.


Although the unused pixels above and below the 16:9 image are "off" - there still is some light leakage. That's why

digital projectors don't have the contrast ratios that CRTs do - they can't do "black" as well.


Dr. Gregory Greenman

Physicist
 

·
Banned
Joined
·
770 Posts
Actually........A digital projector could have a contrast of 3000:1 (on line with a CRT) and still could have light above and below the image. The light leakage has nothing to do with the contrast ratio. It's a projector inability to produce absolute black. So the correct answer would be that a digital projector still has some light output for the color black no matter the contrast ratio. Black bars are here to stay until the Lumen output for the color black is reduced or eliminated.


Dr. Abrams (ok I'm not a doctor but it was too fum poking fun of people that sign Dr. Anything) Sorry Morbius.
 

·
Registered
Joined
·
4,525 Posts
Quote:
The light leakage has nothing to do with the contrast ratio. It's a projector inability to produce absolute black.
Hi AJ


I don't mean to be picky, but doesn't the projector's inability to produce blacks have everything to do with the contrast ratio?

Quote:
So the correct answer would be that a digital projector still has some light output for the color black no matter the contrast ratio.
I suppose that could be true with most front projectors today, but it's not a mathematical truth, and who knows what the future will bring (GLV? Painted laser images?).


Take an LED light display sign (think "Vegas"). It's a digital device. When the "pixels" are off, they are off. If the LED pixels have even a dim light output when on (not the case, actually), the sign has an infinite contrast ratio. Black level has everything to do with contrast. I don't really understand that statement.


You're right that we don't have infinite contrast digital front projectors today, but it's not beyond what's possible. It's just the current state of things.
 

·
Banned
Joined
·
770 Posts
no contrast ratio is a RATIO.....nothing to do with absolute black. the ratio of 3000 lumens (in white) to 1 lumen (in black) is the same to a 6000 lumen (white) to 2 lumens black. The 2 lumens black is twice the absolute black. You can gain contrast ratio with a projector by keeping the absolute black the same but raising overall lumen output......does that make the blacks better? no. Still have the same bars top and bottom. Just makes the contrast ratio better. That last statement of yours is dead on. This is not a ***** just clarification that contrast ratio and the black bars top and bottom of a 16:9 image out of a 4:3 projector have nothing to do with each other contrary to what Morbius states. It has to do with the absolute black level of the projector. If one believed that it has to do with contrast ratio, they might be inclined to believe that a higer contrast machine will make the bars go away. It won't.


If you can get absoulte black lower while maintaining overall brightness, obviously the contrast ratio will improve, but the opposite is true also.
 

·
Registered
Joined
·
46 Posts
You can go to
http://www.dlp.com

and see for yourself how these dlp chips work on producing black, grey, and white and color.

I read somewhere the other day about digital proj of Star Wars II, he said that if the scene is dark, the black is dark grey, but if the scene has enough contrast, the black is dead on. It's actually the same black. It's our eyes that's tricking our mind.

When you put 95 % grey value next to bright white (or bright anything), it looks blacker than it actually is.

That's why with high contrast ratio, the black looks better.
 

·
Registered
Joined
·
4,525 Posts
True. And with infinite contrast, the black is better.


CRT projectors can do it. Telaria laser painting projectors can do it. LED signs can do it. Grating Light Valve projectors...who knows...


Someday, we will have infinite contrast digital projectors that mortals can afford. Someday might be a long time, though....
 

·
Banned
Joined
·
770 Posts
would be nice..would also be nice to have an internal mechanical masking devise that would block off all light when going into different aspect ratio's. It would be a stop gap solution.
 

·
Registered
Joined
·
38 Posts
When I saw a demo of the JVC 150cl D-ILA, the JVC rep (who was not that experienced with the set-up) zoomed the image to fill the width of the screen (which was a 57" wide 4:3 screen). When we watched a DVD, not only were there black (or dark grey) bars above and below, but there was a border of light cast beyond the screen by my recollection at least 12-16" to each side and I believe above and below as well. Is this light spill? Is this halo? Is this the product of an incorrect set-up or is it a normal situation with the JVC D-ILA? If normal, will this light "spill" be COMPLETELY absorbed by masking? What about the ??narrower masking that would be present on an electric masking integrated with an electric screen? And further, if I want no "dark grey" bars, I know I can do 4 way masking. If I used a Panamorph lens, and the proper scaler, could I fill the 16:9 screen, never have to move the Panamorph out of the way (I would want it INSIDE the hushbox if possible), and then would I still need masking to not see black bars, and would that masking need to be horizontal, vertical, or both???? I have followed many many threads here, but I am still very confused...I just know that I don't want black bars, I am not a tinkerer, I want the Panamorph in the husbox IF I need one, I don't want to open the box to move it away for certain aspect ratios. HELP!!!!!!!!!!!!!!!!!

Robert
 
1 - 10 of 10 Posts
Status
Not open for further replies.
Top