on LCD projector, black is not black!
francine frensky
the LCD projector, i had just assumed the projector would show no light in
the black areas...nope! anyway to do that? looks more elegant.
Joel Farris
An LCD projector, simplified, is a series of colored dots being manipulated
semi-randomly with 10,000 flashlights behind them. When you point this
arrangement at a projection screen, which BTW, is designed to reflect any
light it receives back to the audience, you will see a bit of light/color bleed.
Think of it another way. If you hold a piece of black paper up in front of
your car's headlamp, does any light get through? Same story with the LCD
panels, they can only block so much light. Maybe 99% is blocked, and the
remaining 1% hits the screen as a dark, dark grey color.
I run into this problem a lot in theatre productions where moving video sets
the background, then goes to black as the performers hit the stage. The LCD
projectors cast that faint glow, which causes the actors to project 12 foot
shadows onto the back wall! Since you can't really power down a video
projector 20 times during a play [reliability goes out the window] we had to
rig a dowser/shutter in front of each of the lenses to bloct their faint output.
More info than you wanted, I'm sure, but hopefully you get the picture.
--
Plus3dB Productions, LLC
Setting new Levels of satisfaction in the Industry
*************************************************
Joel Farris (818) 292-0444
"HTTP Error1.1 = server too busy. Sound like your life?"
Brad Dunzer
How do you project Black? Since Black is the absence of light thus we get
into a issue. Now modern polysilicon projectors are made up usually of three
paths of light; Red, Green and Blue each combining into a single stream of
light then out the lens. So how does this work. All paths full-on produces a
dark screen, black if you wish.
But we have another item to consider. You see this is issue is huge for a
little thing call contrast ratio comes into play. And the bigger issue of
projector manufactures, more contrast mean less lumens or light to tell the
world your project has. Its the old game of mine has more.
Now some things you can do to correct your problem are depending on the
model of projector and technology driving it. If you can find the menu on
the projector try cranking the contrast up and down and notice how this
effects the dark areas, now also notice what it is doing to the image on the
screen. Honestly, some products just can not do black for many reasons one
being quality of hardware and embedded software.
Newer products do a much better job of producing black and DLP or Digital
Light Processing types of projectors by far have the best contrast ratios on
the market for the cost.
Its really a crap shoot as to what your product can do, and unfortunately
sometimes there is nothing you can do about it.
--
Brad Dunzer
AzureMedia
www.azuremedia.com
"francine frensky" <lovenha...@ivillage.com> wrote in message
news:KkL37.11084$Up.3...@sea-read.news.verio.net...
villem teder
<brad....@azuremedia.com> wrote:
>Well the issue is pretty big.
>
snip...
>
>Newer products do a much better job of producing black and DLP or Digital
>Light Processing types of projectors by far have the best contrast ratios on
>the market for the cost.
>
snip...
Yes, a big problem. It's kinda surprising how sensitive the eye is to
low levels of light once it has adjusted. A physical douser is about
the only way to guarantee real black. Many of the larger projectors
now include one, controlled off the remote. Quite often when doing
Surtitles for opera or theatre, we have to note cues to douse,
depending on lighting cues.
While DLP offer the highest contrast ratios, TI is working on DLP
chips incorporating "Dark ... (something or other)", basically extra
absorption of stray light, specifically for the e-cinema market, where
contrast ratio is an issue.
From propaganda a friend brought back from Comdex, it seems the
highest contrast ratio currently being offered is in the JVC-Hughes
D-ILA series, 1,000:1 I think.
Actually, I think the best contrast ratios available are in CRT-type
projectors. While you would think they would have become dinosaurs
with the advances in LCD and DLP technologies, there was one mention
in the Comdex literature of a new CRT projector aimed at the high-end
home market, Runco, if I remember correctly.
Villem Teder
Toronto
Paul Jackman
just being elegant, it increases the display area without concern for
borders. I very seldom use screens, because of the same limitations.
Black cannot be projected, it is simply the absence of light. Black will
take on the color of what ever it is projected on. To the eye, black will
seem to be darker when a contrasting bright light or color surrounds it or
is adjacent to it. There are possibly 3 ways that may help with your black
background. (1) Change the contrast and brightness levels of the projector.
(2) Increase the ambient room light, especially if the projection is the
only source of light in the room. (3) Don't use a reflective screen, use the
wall, you will be surprised how well a black background presentation can
work
even on a dark wall, blacks will look darker the trade off is white will not
be quite as bright.
If you use the limitations to your advantage you can create a very elegant
presentation. 3D looks better, it is easy on the eyes of the viewer, and
many more special effects can be deployed.
Always use black backgrounds. If you have a bright slide decrease the size
and place it on the slide as a picture.
Try black text with white shadow on black background .
Try layered objects with 3D PowerPoint animation on black backgrounds.
If at all possible, create the presentation using the projector, not the PC
monitor while you are assembling the slides. you will learn quickly what
works and what doesn't. with black backgrounds.
Regards
Paul Jackman
JackTech
"francine frensky" <lovenha...@ivillage.com> wrote in message
news:KkL37.11084$Up.3...@sea-read.news.verio.net...
Paul Jackman
Simon Livingstone
Plus3dBPr...@att.net wrote on 14/7/01 1:17:
> francine frensky wrote:
>>
>> i have a series of slides with black backgrounds. when i project them using
>> the LCD projector, i had just assumed the projector would show no light in
>> the black areas...nope! anyway to do that? looks more elegant.
>
> An LCD projector, simplified, is a series of colored dots being manipulated
> semi-randomly with 10,000 flashlights behind them. When you point this
> arrangement at a projection screen, which BTW, is designed to reflect any
> light it receives back to the audience, you will see a bit of light/color
> bleed.
>
> Think of it another way. If you hold a piece of black paper up in front of
> your car's headlamp, does any light get through? Same story with the LCD
> panels, they can only block so much light. Maybe 99% is blocked, and the
> remaining 1% hits the screen as a dark, dark grey color.
>
> I run into this problem a lot in theatre productions where moving video sets
> the background, then goes to black as the performers hit the stage. The LCD
> projectors cast that faint glow, which causes the actors to project 12 foot
> shadows onto the back wall! Since you can't really power down a video
> projector 20 times during a play [reliability goes out the window] we had to
> rig a dowser/shutter in front of each of the lenses to bloct their faint
> output.
>
> More info than you wanted, I'm sure, but hopefully you get the picture.
You could use a projector with a shutter fitted like a Barco LCD/ DMD there
are many to choose from.
Simon Livingstone
Windmill Studios
49-59 York Road
Brentford
Middlesex
TW8 OQP
Tel: 020 8568 0462 Fax: 020 8568 4151