Interest in 22" EFL w/ 5" Diameter Opaque PJ lens?

[rlwoodjr]

I have been doing more experimenting.

The 22" beseler at 115" from the screen 23.25" from the 17", 16:9 format LCD (transparency) will good focus corner to corner. using a 550/220 combination. The setup has to be exact for even lighting. I think this would be improved with a 650/220 fresnel combination. Lumenlabs are still on back order.

I also have a 22.25 EFL Ednalite that is about a 2.25" glass diameter that has great corner to corner focus with the same set up, but it is a little dimmer. I think this will be helped with the 650mm fresnel.

I guess I will have to wait until I can find a 650 mm fresnel to be sure. Anyone have one they want to sell?

[Guy Grotke]

I am using the 22" lens now with a 15" Proview LCD, 220 condensor fresnel, and 550 field fresnel. I have the lamp arc only about 182 mm from the fresnel, to get the arc image into the projection lens. Not bad at all: I see pixels and screendoor all over the screen. I can focus the red, green, and blue subpixels at the center and still make them out at the edges (but they are not as sharp).

A 650 mm fl fresnel would be perfect for this 22" fl projection lens: Then I could put the lamp arc at the condensor fresnel's focal length and get more light through the fresnel.

The 550 mm fl fresnel was designed to work best with projection lenses around 450 mm fl, like the large DIY projection store triplets or the very common 18" opaque projector lens. (Given that those are the most common long throw lenses used by the DIY projection community, it made business sense for 3dlens to make it 550 mm fl.) I have used the 550 fresnel with an 18" opaque projector lens, and it works great. (I am using the 22" lens now just to get my projector to the back of the room.)

Another major improvement (at least for a Proview PL566s): I removed the antiglare diffusor layer from the front of the LCD last night. Pretty simple to do. I just dissassembled my LCD frame so I could get to the edges of the glass surface, laid water-saturated paper towels on the surface for 2 hours, and then peeled it right off. It all came off in one piece with minimal effort, and left a perfectly clean polarizer surface with no cleaning needed. Now my LCD is much more transparent, so I get a pretty clean arc image at the projection lens. Since all of that light makes it through the lens, I see more light on the screen.

[rlwoodjr]

I have the Westinghouse LCM -17w7. Do you know if anyone has has success removing the antiglare on this monitor?

[Rox]

if i am not wrong, you have a luxmeter GG, (or it was sent to you by mike P so now you don´t have it...?)

did you check the real antiglare remove brightness improvement for you? This is something I hardly find on forums. Aslo would be interesting if contrast improvement was meassured after antiglare removing (if any).

thanks.

[Guy Grotke]

I liked Mike's LuxMeter so much that I bought my own. (Cheap on eBay) So I actually do have some numbers. Before I removed the AG layer, I got somewhere in the low 70s Lux at the center of a totally white screen image. Now I get over 130 Lux... But it is not quite that simple. Let me explain:

Before I removed the AG layer, I tuned the fresnel and lamp distances to give me an arc image at the center of my projection lens with the LCD removed. When I would add the LCD back into the system, I would not get a visible arc image near the lens. Just a big blob of light, larger than the lens diameter. (That indicates that some of the light will be lost.) I could change my fresnel and lamp distances, but with the LCD in place I always got a big blob of light. So it was not really tunable!

After I removed the AG layer, I still got around 71 Lux at the center of my screen. But then I adjusted the lamp and fresnel distances to see if I could do better. I found that I could see a very clear arc image when I removed my projection lens and held up a piece of white paper. It was focussed several inches before my projection lens. So I adjusted the lamp-to-fresnel distance, until I got an arc image right at the center of the projection lens position. That is how I got it to over 130 Lux. Now I can even see the arc image on the lens surfaces when I look into the lens. All of the light is coming into a band about 4 inches wide and 1.5 inches tall (lens is 4.25 inches diameter), so most of the light now gets through the lens.

So the real answer is:
If you have an LCD with a bad AntiGlare/diffuser layer
..If that AG layer can be removed without damaging the LCD
....If you then tune the distances to get your arc image into your lens
......Then you can get a great benefit.

If you just remove the AG layer and fail to tune it, your image could actually get dimmer. That would mean that your system is so mis-adjusted that the light getting through your lens had to be diffused to get there.

I have not measured the contrast, since the dark areas are below my Lux meter sensitivity. (1 Lux)

[Rox]

I am assuming you doubled the lumens output (assuming same image size and as the lux value doubled at center.... or is it the vigneting much worse now?)

yea, this is a problem with the luxmeters, i can´t either meassure lux values lower than 1 lux. But I found a "somehow" solution;

place the luxmeter somewhere bettween triplet and projection (near in conctact to the triplet), this way both meassuremnts (white and black fullscreen) will grow up, somewhere 20 lux for the black and somehwere 8000 for the white... this would be 400:1 contrast. Just take care of some luxmeter holding system so it does not move...

this is not ansi contrast measuremnt but is a good enough one. The problem is that you didn´t know the contrast with the antiglare there.... but you can compare this contrast to the one estated by the TFT....

anyway, do you perceive any improvement visually?

[Guy Grotke]

When I have a totally black image on the screen, I do see some artifacts. Some areas are a bit lighter than others. But in my experience, that generally is a product of slight misalignment of the light source and fresnels. I will try some adjustments of that in the near future.

When I have a very bright area slightly off-center of the screen, surrounded by very dark areas, then I can see a slight reflection of the bright object in the dark area. This is reflection from the lens, back to the LCD, and then back out through the lens. I think a lens with Anti-Reflection coating would work better with an LCD that has the AG layer removed.

The corners now appear like they are as bright as the center, to the eye. (I know they are at least 1.84:1 by the inverse square law effect on lamp to LCD.) So even with the added artifacts, the picture is much improved. When I am watching video, the uniformly bright appearance is much more important than the slight defects. I only notice the defects if I look for them, and then only because I know what to look for.

I don't really worry about contrast ratio much. I am using a 300:1 LCD, but screen light that gets reflected back from my white walls will lower the contrast much more than that. Sometimes I even have a light on in an adjacent room! No sense getting worked up about it unless you want to build a home theatre with black curtains on all the walls, etc.

[Rox]

Originally posted by Guy Grotke
This is reflection from the lens, back to the LCD, and then back out through the lens.

well, this is the advantage of antiglare, but there would be an inconvenience as well, the light control with the antiglare there would make a dimmer image because of difusivity, so what you prefer? a sihgly lower contrast image (light artifacts) or a brighter image?

did you paint the triplet side flat black?

[Guy Grotke]

The LCD antiglare layer works fine as antireflection with standard backlighting, but it diffuses the light too much for projection. An antireflective coating on the first lens surface would be much better, since it would not send much light off in other directions.

If it was just 10% brighter, then I would regret removing the Ag layer. But it is so much brighter that the picture looks MUCH MUCH better. If I get the lens coated, then that should take care of the reflection artifact. I don't think I will bother. Like I said earlier, I don't even notice it unless I am looking for it.

[Rox]

the typical triplets are antireflection coated already (the 3 lenses)... well, maybe it is not the best coate (multicoated with a greenish color is best) but i think it is doing good work.

Do you think it is the lens surface itself what reflects or the enviroment of the lens?

Tell me, did you paint flat black the sorrounding area?