[herecomethebugs]

Has anyone researched/experimented with this? Does painting the inside of your box help in anyway?

I'd be interested in hearing your theories about this... I see some have painted the inside black -- I would think that would be a bad idea since black essentially absorbs the light? What do you guys think?

[zendance]

herecomethebugs, on Sep 16 2004, 02:07 PM, said:

Has anyone researched/experimented with this? Does painting the inside of your box help in anyway?

I'd be interested in hearing your theories about this... I see some have painted the inside black -- I would think that would be a bad idea since black essentially absorbs the light? What do you guys think?

I haven't done this yet. But the consensus seems to be that painting the part between the projection lens and the LCD provides better light control. The reason is, the projection lens will still transmit reflected light off the sides of the box interior. This could wash out the image a little. I still plan on painting mine, I just wanted to fix bigger problems I'm having first.

For the same reason, you want to seal the edges around your LCD to prevent stray light from the lamp. I did experience this problem and it actually caused a white line to show up on my screen.

[herecomethebugs]

What about painting the walls around the bulb too? From what you say, this would simplify the amount of light bouncing off the walls. The majority of the light would be coming from the light and bowl reflector... Or is it better if some of the light bounces off the walls of the bulb compartment being that the fresnel collects the light and focuses it forward – does the fresnel act the same way as the projection lens in that it transmits the reflected light and slightly washes out the projected image?

[zendance]

herecomethebugs, on Sep 17 2004, 04:15 AM, said:

What about painting the walls around the bulb too? From what you say, this would simplify the amount of light bouncing off the walls. The majority of the light would be coming from the light and bowl reflector... Or is it better if some of the light bounces off the walls of the bulb compartment being that the fresnel collects the light and focuses it forward – does the fresnel act the same way as the projection lens in that it transmits the reflected light and slightly washes out the projected image?

Painting the area around the lamp doesn't seem to matter. The Fresnel really only transmits light that comes from the bulb and what little reflected light it does transmit is very small in comparison unless you did something like mirror the inside of the box. (not recommended because it's very hard to get even lighting that way)

I would recommend using the Norpro bowl as a reflector, however. It seems to up the brightness by something like 60%.

[AllThumbs]

I ended up painting the entire interior of my box flat black.

The entire light chamber is covered in aluminum flashing, and the additional reflectivity bounced out the fan and other openings. Painting it flat black reduced the reflectivity and light spillage. The difference was noticeable. Less light spillage meant less ambient light and improved image brightness.

The bulb is so bright, it reflects off everything -- the interior walls, the flashing, even the circuit boards. Completely sealing the interior affects cooling.

My first LCD was dimmer than my second. The current LCD is plenty bright, especially in conjunction with a Norpro. The Norpro pushes most of the light forward; reducing the reflectivity in the light chamber allowed me to just have a hole for the fan (no grates or light boxes).

[SethAce]

Norpro the mixing bowl set ?.... Hrm... I had never thought of that... I mean I saw the norpro refrence a few times but I just google searched it and it's tortilla bowls is this the right norpro or am I once again lost..

[AllThumbs]

Yes, a Norpro mixing bowl. Here's an interesting thread that discusses it.
Pinned: Reflection Thread

Hey, we're also ripping a standard LCD monitor to shreds, using an overhead warehouse lamp as a light source, and have attic thermostats as automated fan controllers. Mixing bowl as a reflector? How McGyver do you want to get?

[SethAce]

Well if you really wan to go mcguyver then where is the chewing gum wrapper and chewing gum coming in.. Thanks for letting me in the loop I was a little lost I'm not the brightest, but I catch on quickly..

[jeremyvnc]

I can vouch for the differences between the painted box and the non as well as with and without the norpro. I did get a somewhat washed out image when I didn't paint the box. Afterwards the picture was very clean. The norpro does add a considerable amount of light to the projection and it keeps the components like powersupply and ballast cooler because they are not getting a sun tan .

[Ronjon]

jeremyvnc, on Sep 20 2004, 07:09 PM, said:

I can vouch for the differences between the painted box and the non as well as with and without the norpro. I did get a somewhat washed out image when I didn't paint the box. Afterwards the picture was very clean. The norpro does add a considerable amount of light to the projection and it keeps the components like powersupply and ballast cooler because they are not getting a sun tan :).

Hi Jeremy,

I have few question,

Are you talking about painting the bulb side of the box?
Did you have aluminum flashing that you painted?
Did you use regular flat black or high temperature flat black (500' F or higher)?
If you used regular flat black how many hours have you run it? Did it peel off at all?
Did you use primer on the flashings before painting them flat black?

I will appreciate your input on this matter.

Ronjon

[AllThumbs]

Quote

Are you talking about painting the bulb side of the box?
Did you have aluminum flashing that you painted?
Did you use regular flat black or high temperature flat black (500' F or higher)?
If you used regular flat black how many hours have you run it? Did it peel off at all?
Did you use primer on the flashings before painting them flat black?

I'm not Jeremy, but...

Yes, we're talking about painting the bulb (lightbox) side.
I painted aluminum flashing on the lightbox side, and bare wood on the projection side.
I used high temperature black (bbq grill paint) for the aluminum. No primer was used for either aluminum or wood. (Primer is used to establish a firm base, and prevent stuff from showing through. This isn't for looks, just to kill the reflection.)

I also used flat black acrylic paints on some of the wood.

There has been no temperature problem. The hottest point is the spot on the lid just above the bulb. ~1 inch above the bulb was 235'F. Interestingly, the aluminum at that point on the lid feels the same as the rest of the lid (not even warm). I believe aluminum conducts the heat effectively throughout its surface, and the fan cools it before it can heat up.

The pj has run for hours and hours now (2-5 hours a day for almost two months). Nothing has peeled.

[Ronjon]

Thanks for the info.

I am assuming the hot paint you used did not require curing. I have a can of paint rated at 1500' F that needs to be baked at 650' F for an hour. This is engine paint. If not cured, it will rub off when handled.

Your paint may not require curing. Or since they use it on the BBQ grill, it may cure when the grill is in use.

I will check at the hardware or auto store.

Ronjon

[Skanmyth]

SethAce, on Sep 20 2004, 06:49 PM, said:

Well if you really wan to go mcguyver then where is the chewing gum wrapper and chewing gum coming in..

SethAce,

Some using stiking putty to do there key stoning if they runout of stiking putty then they can use chewing gum

[SIMJEDI]

IMO the bulb box should be painted a flat white, nice smooth even light distribution, and I would not ever use regular shiny alluminum flashing, to much bouncing and loss of light, plus white is much, much brighter, the idea here is to be bright.

For the projection lense housing area I would use nothing else but black Duvetyne, also known as Commando Cloth. The light absorbing properties of this stuff is amazing. You can also use black velvet found at JoAnn Fabrics but that has more of a tendency to break off and float around. I have seen a frightening trend here with people putting the electronics in this section left out in the open. Any ambient light bouncing off of all them shiny parts and into the lenses will most likely degrade the picture.

Hope this helps, man I love this place


peace

[Skanmyth]

SIMJEDI,

Let us know your results of your PJ when you paint white on light area.

Good luck on building your PJ. hope to see your results soon.

[herecomethebugs]

Black duvetyne sounds like a good idea... you could use it to cover the LCD circuit boards along with the walls.

The only problem is the duvetyne might act as a heat insulator on the circuit boards. Do the LCD circuit boards put off enough heat for this to be a concern (Is there anything on the circuit boards that gets hot)? Maybe someone that has a working projector could answer this? I haven’t stripped my monitor yet.