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DLP displays do have some advantages, but their rapidly spinning color
wheels can cause problems.  Color wheels are susceptible to mechanical
failure, and they also introduce rainbow artifacts which make them
unsuitable for specific uses (e.g. our exhibit "Magic Wand").
Interestingly, about 10% of people notice disconcerting rainbows even when
watching ordinary movies with DLP projectors, mainly when they're projecting
bright lines or spots on dark backgrounds.  But you can also make a feature
out of this bug, and use DLP rainbows to demonstrate how our visual systems
process rapidly changing colors;  they're the temporal analog of spatially
discrete RGB pixels.

Has anyone had any luck with solid state projectors, which use LED and/or
laser light sources?  The new ones are just starting to get bright enough
for museum use (1000 - 2500 lumens), and could offer some advantages.  But I
don't know how well they handle heat and dust under heavy use.

-Richard


On Wed, Apr 14, 2010 at 10:53 AM, Eric Socolofsky <
[log in to unmask]> wrote:

> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related
> institutions.
>
> *****************************************************************************
>
> it's definitely a heat issue.  be sure to change your filters as often as
> your maintenance schedule allows (optimally once/month or more) and make
> sure your projectors are in a well-ventilated area.
>
> but yeah...LCDs just tend to discolor with age (faster if they're running
> too hot).  that's one of their disadvantages.  you can always get them
> repaired by the manufacturer, particularly (of course) if they're under
> warranty.
>
> -eric
>
> Date:    Tue, 13 Apr 2010 09:57:25 -0700
> > From:    Allan Ayres <[log in to unmask]>
> > Subject: Yellow spots in video projectors?
> > MIME-Version: 1.0
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> >
> > ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> > Incorporated, a worldwide network of science museums and related
> > institutions.
> >
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> >
> > Hi everyone,
> >
> > I posted this yesterday on the Science on a Sphere list, but I figured
> > I'd ask here as well.
> >
> > I'm wondering if other video projector users have had yellow spots
> > develop in their images over time.  We've particularly had problems
> > with Sony projectors, including two of the VPL-FE40 units in our SoS
> > installation and an older VPL-PX40 we took out of service a few years
> > ago because of the spots.  (We don't have experience with any other
> > brands, so I don't know if they have similar problems.)
> >
> > I dug out the old VPL-PX40 and took it apart, and it appears to be the
> > blue LCD element itself that has the splotches in it.  That's a
> > bummer, as I suppose an LCD panel is more expensive to replace than,
> > say, one of the polarizers or other little plastic filters that are
> > scattered around the system (i.e. probably some significant fraction
> > of the cost of a new projector).
> >
> > Anyway, I just wanted to throw the question out to see if anyone else
> > had faced this problem.  If so, has anyone had any success with
> > getting projectors repaired and/or cleaned?
> >
> > Thanks!
> > ~~~~~~~~~~~~~~~~~~~~~~~~~
> > Allan Ayres
> > Exhibit Developer
> > Lawrence Hall of Science
> > University of California, Berkeley
> > Berkeley, CA 94720-5200
> > [log in to unmask]
> >
> > ***********************************************************************
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> > Date:    Tue, 13 Apr 2010 11:07:57 -0600
> > From:    Bruce Wyman <[log in to unmask]>
> > Subject: Re: Yellow spots in video projectors?
> > MIME-Version: 1.0
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> >
> > ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> > Incorporated, a worldwide network of science museums and related
> > institutions.
> >
> >
> *****************************************************************************
> >
> > >I'm wondering if other video projector users have had yellow spots
> > >develop in their images over time.  We've particularly had problems
> > >with Sony projectors, including two of the VPL-FE40 units in our SoS
> > >installation and an older VPL-PX40 we took out of service a few
> > >years ago because of the spots.  (We don't have experience with any
> > >other brands, so I don't know if they have similar problems.)
> >
> > I've seen it as a problem with LCD projectors, never with DLP
> > projectors. We usually see it as a blue haze forming around the
> > periphery of the projected image which eventually spreads across the
> > entire image like a cataract (primarily with Viewsonic projectors
> > (PJ1172, which are really rebranded hitachis)).
> >
> > I have the unique case of being at higher altitude than most other
> > people (we're about a mile above sea level) and I think the
> > underlying issue is one of heat. At altitude, we just have less air
> > to move around to cool off the projectors (and lower end projectors
> > don't have a secret altitude setting in firmware). Every LCD
> > projector I've used eventually has problems with the screen closest
> > to the heat source in the projector. The problem is definitely
> > compounded if the projectors are being used outside of the
> > recommended angles and positioning of the manufacturer.
> >
> > I've talked with Sony, Hitachi, and Panasonic reps and I've never had
> > a consistent answer so the above is a bit of conjecture. But, for
> > stuff that we're using in exhibits and where airflow may be a
> > potential issue, we're using DLP projectors exclusively.
> >
> > -bw.
> > --
> >
> >
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> > Bruce Wyman, Director of Technology
> > Denver Art Museum  /  100 W 14th Ave. Pkwy, Denver, CO 80204
> > office: 720.913.0159  /  fax: 720.913.0002
> > <[log in to unmask]>
> >
>
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