Click to view attachmentClick to view attachmentJust got my new fresnels and put them in my box.I have everything lined up pretty much right on, could prob use a little tweaking but its close.I turned on the power and waited about 20 mins to make sure the bulb got warmed up,well its not that bright.I then put my 4000 lumens overhead projector next to my LL projector for a comparison and my over head is at least twice as bright as you can see from the pic. It has to be the bulb im using because if this is as bright as it gets,its not good.I am using the mh 400 phillips and the Ikea blanda bowl for a reflector which i know is not the best but jeez, should not be this bad.The bulb gets real bright and white in the box, but is the arc too big and thats the prob? Forgot to say the top half of the screen is the LL and the bottom is the overhead projector

Wow, that's a big difference. Have you tried moving the bulb closer/further away from the first fresnel?

Also, isn't the MH bulb going through a LCD, while the OHP is all clear?

It'd be interesting to see the results if you pulled the LCD out and just ran with the bulb and fresnels.

There is no lcd in the box yet, both are just light through the fresnels.I did not try moving the light closer to the first fresnel yet, but i am 8 and 3/4 inches away from the first fresnel,and i forgot to mention the box is painted black and im using lexan for the uv shield, and the fresnels are split.Everthing is placed to the standard LL design.When i have just the LL projector on its looks pretty bright but,when i compare with the overhead its like wow!

Good comparison exercise!
I'd try going with an 8" fresnel/bulb distance and make sure your fresnels are not reversed or backwards. you should get at least similar levels as the OH pj because you have about 3 times the light output on the MH even though its not as concentrated.

1) Make sure to make the white images the same size. It looks like the OH is making a lot smaller image so it will naturally be a lot brighter.

2) Make sure you keep the outputs seperated and don't overlap the OH onto the LLPJ output.

the 410 haloge bulb is likely about a 12,000 lumen net output. while the MH is closer to 35,000 . The Overhead likely has better optics at the bulb end of things so it can catch nearly 30% of the light output ( that gives you the 4000 lumen rating?) Wtih the LCD removed and a fair reflector you "Should" be getting around 3500 lumens on the screen. Again make sure the output is spread over the same total area when comparing the brightness of the two.

Cheers,
Kirk

Just a few questions for thought.

What kind of reflector does the overhead projector use? Maybe it'd be an option for a reflector.
Is your bowl polished to a mirror image?

Interesting... but a few questions.

Are the projections overlapping ? I mean, where is the bottom of the LL projection ? I can see the top of the OHP projection pretty clearly. Is the light in this area additive if they are overlapping ? Could be one reason for the brighter area. Also the color (K) of the bulbs are different and will "exaggerate" the light intensity when using a digital camera. Are the results you are seeing with your eyes the same as in the picture ? (i.e. many people will report that screen shots are not accurate in reproducing how it appears in person, often this relates to the brightness of the image)

Am I correct in assuming the halogen is the one that came with the OHP ? ... and has a built in reflector ? If so, we know that a bulb with built in reflector makes much more efficent use of the available light, while the LL design suffers from the MH lamp/"bowl" type reflector setup. The reflectors used in the OHP are ellipical reflectors which are much better, but also much more expensive, and have not nearly the life. All you have to do is look at a commercial setup. Aren't this basicall the same .?

Am I off base here ?

cheers,
gs

The reflector in the overhead is the the built in reflector around the bulb, which is an fxl bulb and the mirror.I know the overhead is optimized for the point light source and will naturally be better from the get go.I actually put the mh 400 in my other overhead which is the same apollo 2250 with a little modding, and got the same results as far as brightness as the LL projector.The blanda bowl is stock from ikea i did not polish it any further yet.The triplet im using is also from the other overhead so they are the same.I am gonna really go to town on this today to try to tweak it.It is really cool to have this comparison to try to optimize the LL light output i just hope i can get the LL to equal my overhead, thats the reason i im doing this because i thought the LL projector would be alot brighter.I am wondering how a metal halide overhead projector would stack up as far as brightness goes.

This result doesn't surprise me (very much ). I would guess overhead projectors are optimized with respect to light transmission and utilization of the bulb light output. There is a plog here (forget who's) that is a conversion from and overhead projector to a LL design and his results are quite breathtaking.

One thing that struck me while just experimenting was the amount of light that is reflected the fresnels and lexan surfaces. I used a flashlight (probably not fair because it is not a point source) at the FL of the collimating fresnel in a totally dark room just to get a feel for how the optics work. Amazingly, the light "splotch" that was reflected against the back wall was much brighter than the projected light "splotch". The LL design is brute force in this respect; there is a lot of loss, so we compensate with a much stronger bulb. I don't know if anti-reflective coatings are possible with plastic, but it would be interesting to see how much that would increase light transmission... An elliptical reflector would also help matters by utilizing more of the bulb output.

This is PURELY a guess, but I would say that the light output of the LL projectors is around 150-200 ANSI lumens. Around what the old CRT projectors put out.

I just looked at your picture again. Are you sure you dont have the fresnels swapped?

Well i have been trying to tweak the brightness, and have tried everything.I tried swapping fresnels, moving the light closer, the fresnels closer, and further back,moving around the reflector and no difference.The only thing i can think it could be is the triplet, but i dont think the triplet is going to effect the brightness that much.I am using the exact same triplet that is on the overhead.I have the projector about 9 feet away from the screen and i get about a 10 foot projection.My screen is a 7x7 dalite screen. How can i get the picture size down without moving the projector back. when i try to focus it just gets to big or it goes into a circle?Maybe the triplet is not the right focal length?I have tried to look it up on the web and cannot find any info, Apollo 2250.As far as overheads vs the LL projector this was my worst fear, buying all the stuff only to find out its not as good as my overhead setup, because my overhead setup looked awesome.I just wanted everything enclosed in a box for light leakage and i heard so many good things about the LL projector.I hope i can get it as bright as my overhead, then i would be happy.Also would the ushio bulb with the napkin holder give that much more brightness?

it is difficult to use a non LL triplet with the LL lenses, as the focal length probanly is not the same. I know that while I feel my brightness lacks the punch that is needed, it is brighter than that. However, the over-powering light from the OH pj may just be making the LL look less bright as ambient light would. A pic without the OH pj on will help to let us see the actual LL PJ's brightness.

Click to view attachmentClick to view attachmentOk here are two seperate pics, now the weird thing is the LL looks brighter than the overhead in the picture than in real life.This might sound stupid but could the LL be brighter even though it does not look that way to the naked eye?The overhead pic has the rounded corner at the bottom.

You can't compare two seperate photos. The auto exposure will be adjusted to make the dimmer one look brighter. You are better off doing a side by side at the same time. Don't worry about ambient light - that will be equal for both.
Move your projectors closer to get a smaller more managable picture.

Kirk

I didnt think about that, i will have to take some more pics later, my wife is taking my camera to a party tonight.I wish i could take some pics with the lcd in but LL forgot to put my ffc cable ext in with my fresnel order hehe.

Oh and a side note halogens are supposed to be more yellow than mh bulbs seems thats whats coming up in the pics.

yes, those photos will work, but as stated above, taking individual photos will change exposure based on available light. If your camera has a manual mode take the first photo in automatic, then set the camera in manual mode with the same aperture (f/stop) and shutter speed as the first photo. This is another way to make the photos comparable, but getting two smaller images setup side by side with one photo will still make a better comparision.

I think I see your problem... at first I thought you had your lcd powered in your lumenlab, but you said your still waiting for your ffc ext.

The problem is that the lcd, when not powered is not clear! ( unless it is in a standby mode). It will provide lots of resistance to the pass through of light.For example... with mine if I go from a dead start( power dead in the box and to the lcd), you can look into the lens and not get blinded.. but turn the lcd on and watch out! When powering off and I shut the lcd down, it goes into its standby mode instead of shuting the screen compleatly off. This keeps the lcd screen open and you get the full white light out of the box. If I was to not uplug the power to the projector, I would get the full light when I turned the projector back on the next time because the lcd would still be in standby. since I do unplug It will go back through the process again the next time.
I hope that makes some sense...

Moose,

From an earlier post he said the LCD was not in during the pictures.

Quote: "There is no lcd in the box yet, both are just light through the fresnels."

The lcd is not in the box at all MOOSE.I am gonna try going vertical with a mirror,the box i have will work perfect the for vertical design,that way i can stick my lcd panel in even without the ffc ext for testing.I am also gonna buy a new bulb because i think the one i have is crap.I am thinking either the sd400 or the double ended.I know the double ended bulb is more pricey but with the soup ladel for a reflector it should provide a much better point light source, correct?

woops, thats what I get when I am trying to answer posts while scaning for no no's.
well since that is not it I would next guess that the fresnels are off or the light is not hitting the triplet fully.
Since there is no lcd than you could try moving the field fresnel back to the collimator and group them together to see if those lenses are or were not lined up. you can also put a piece of paper over the rear of the triplet and see if the light is centered on the lens. Once those are checked then I would try to move the lamp.

Moose,
What brand of LCD are you using?
Mine is clear when off (no power) and when the pixels are active they un-twist to block the light (black). Benq

By your description, yours must use some voltage with forward polarity to go dark and reverse polarity to go clear. No power in effect would be half twisted or half-black.

Kirk

Ok ,
A bit of research shows it depends on the type of LCD.
Looks like three or four various kinds depending on manufacturer. I guess generalizations like "its clear when it's off" Will only apply to some people. (tn+film). others will have super tft , which i think is Moose's. and others different ones as well. Most strives in technology have been to increase viewing angle ( which has little to do with our set-up) as well as response time and contrast ratio.

Cheers,
Kirk

Hi stick,
Im using the samsung ltn1565(s)version lcd tv. Mine also has the ability to control brightness without the backlight.
Kind of interesting as I have only used this lcd and figured it would be a general effect on all lcd's.

Click to view attachmentI just did a test with the lcd in not powered up with both the LL and my overhead and the overhead was alot brighter but, i will have to reserve judgement until i can get the lcd powered up.

By the way here is a pic from my overhead setup just plain old overhead no box no nothing.

It would be great if someone could put a lightmeter in front of these. Maybe there is something to it.

Let's say the overhead has 1/10 the overall lumen output, but has a much smaller point source. Remember, the MH bulbs spread their lightsource across a 1 inch long gas packet. If the optics can only focus in on, say a mm dot, then most of the light may not even make it to the lcd. Those OHP halogen bulbs were specifically made for this type of application. Our MH bulbs were not made for anything like this.

I would love to see a quantitative test.

I agree phutton.I am not worried about how long a bulb lasts as long as its not real expensive.If halogens work better im all for it .I know the color in the halogens might not be as good as the metal halide but i have seen some halogens that have 5200k color 8500 lumens and are 500 watts, and are single ended and about the same size as the overhead bulbs.If we could find a reflector like the fxl bulbs, i think it would produce an amazing picture.Personally i have tried everything i could think of and all the info on these forums to try to match the brightness of my overhead and i cannot do it.Hopfully i am missing something thats easy to fix.

My feeling is that once there is an efficient reflector for the MH bulbs (in whatever form), the LL design will be better in terms of brightness, color and cost... of course never having worked on an OHP setup it's hard to say this with any sort of confidence.

Your OHP image looks great ! Were you thinking the LL design would improve this image, or were you looking at creating a nicer looking box or something ? Also, how does the OHP throw distance compare to that of the LL design ? (perhaps too early to say until you get the LCD hooked up ?)

cheers,
gs

I was hoping to improve image and solve the light leakage problems of the overhead,not to mention the mh bulbs last longer.My overhead is 9 feet away from my screen and im using ffdshow with a manual 2:35 ratio.

Well i finally got my ffc cable and fired up my LL projector and i must say my first impressions are encouraging.I have about 3 things to tweak and i think i can get the brightness up where i want.The main thing i noticed in the LL is the colors are better for sure and the quality is better,just need to mess around with the the ikea napkin holder a little, my triplet is 3/16s off center and my pvc pipe sticks in too far.I also notice that its a little green which i know has been discussed before but i have only had my s400dd on for like 15 mins.I can only assume i need to burn it in more.