The grooves must be facing the monitor. and make sure the measurements are accurate from the triplet.

One more thing. if you get lines in your image how do you fix it?

A fresnel is too close to the lcd.

Thanks man i moved the collector fresnel away from the lcd and it fixed the lines and most of the dark corners.

Hello all,

I need help figuring out what type of ffc extention I need to buy from here. I have recently posted my monitor as incompatible due to ffc issues, but there seems to be mixed reviews on whether it is a problem or not.
Some folks have said that this isn't a problem anymore, but I haven't seen one review in the forum showing any detailed info on the subject (only a link to DIYaudio http://www.diyaudio.com/forums/showthread....10&pagenumber=1 ), like how to count the pins and what not.
It seems fairly obvious, but assumption has got me into so much trouble in the past.
If ffc's really aren't an issue anymore, then I really think the topic deserves more attention in the main forums with detailed information and pics showing how to overcome it, at the very least searching "ffc" should yield results to this info, for me I get the "sorry" message when I search it.
I am not looking for a Flamefest for not being able to find this sacred info, just a little hand holding

Thanks,

found this in the forum ( http://www.lumenlab.com/protectedwiki/Flat_Flexible_Cables ), but it really isn't what I was looking to know either...

Here's a thread explaining how to use the kits from the References and Tutorials section:

http://www.lumenlab.com/forums/index.php?showtopic=4503

For the pitch, just count the number of pins and measure the width of the cable in mm. If the cable is 16mm wide with 16 pins it is a 1mm pitch, and 8mm wide with 16 pins would be .5mm pitch (most common). I'll update the thread to include this basic information.

Thank you for the quick response. I know it must be aggravating to answer all the "common sense" questions that may come up. Your politness in the face of ignorance is appreciated.

Anytime

Now that you know where the thread is, if you have any issues just ask in there.

Listed this somewhere else, but trying to get more help quickly. Fresnels were in the right way btw.

OK, this is what i did over the weekend for the X-mas vaca.--
MOUNTED the new screen AND the BOARD securely-NO TEARS ANYMORE!!!!

Problem-light is bright in the middle. I tried moving the fresnels an either the focus would go out too much or the problem was the same. I then found that by taking out the fresnels; the screen looked the same!!! Do i not even need them?!?!? Should i also not even have a "point light source"?!?

Here are my parts:
-PSone screen
-EIKO MH-DE250/TD
-Surplus Shed Copy Lense #L3138 112mm FL
-4" Fresnels--tried magnifying sheets first so the good lenses didn't get destroyed, but neither makes a difference

I tried the original lense i had too, but it was the same. Through process of elimination; i think it has to do with the light since the pic is the same with no fresnels, and with a different projection lense.

Any toughts now that you know exactly what i'm using? Reflector solve my problem??? If i take the projection lense out and look into the box; i can see the whole screen is backlit from the bulb, but the center is brighter due to the point source. Shouldn't the fresnels actually spresd the light across the screen or are they simply there to "straighten" the light?

Thanks gang! The GF can't wait to finally be able to watch a movie on this thing, so any help is always appreciated!!

split or unsplit fresnels? either way, the fresnels have to pretty much stay in the same place..but try moving the light closer and further away away from the rear fresnel..(once you have a focused projection that is) , a reflector would brighten the picture, nto sure it would do anything about the eveness of the projected light though....

I had the picture on the screen perfect enough to make out the pixels, then i moved the rear lense to no avail. Plus, i get the same pic whether i'm using the fresnels or not. Unsplit or split? I can feel and see the grooves on the side facing the PSone screen if that is what you are referring to .. .. .

no...don't move the lens once you have the focused picture... you move the light bulb closer or farther.... split means one fresnel is behind the lcd , the other is in front of it, unsplit means the 2 fresnels are both behind the lcd(between the light and the lcd).. if those are 4" focal length fresnels, how far from the bulb arc is the one(or both ) from the bulb? how far are they from the lcd? about half an inch from the lcd is right(for unsplit or split) , start with the bulb 4" from the rear fresnel, and then move the light back and forth(and maybe a little sideways too )

OK, i will be home and able to try again tonight. As far as i recall, i have the lenses 4" from the lamp and the other 4" from the projection lense. The lenses are in frames and so is te screen. If i put them right up against the screeen frame(frame to frame) it made no difference. They told me the focal point was 4", but i put it up to the sun and get a nice point at like 9". If i hold it over some type; it is clear from right up against to the 9" or so.

I will try moving the light tonight. Thanks!

well, I'd test your fresnels again for FL...if you get 9" again , I'd try that also.... I remember reading a way to test your collimating(rear) fresnel...you take a candle, the fresnel and a big piece of paper, place the candle such that the middle of the flame is centered with the fresnel, raise it or lower it wih books or whatever)... place the fresnel between the paper and the candle (groove side of fresnel facing the paper(or you can use the wall but you have to be pretty close since candles are only 1 candle power anyway, move the candle closer and further from the fresnel...when the light rectangle projected by the fresnel is the same size as the fresnel, the distance from the candle to the fresnel is your FL ... the sun is good too, but its been cloudy for days here ;-) .....

thanks for the good info! I was checking it like a projection lense-hold it up to "the sun" and move it til there is a "point" and measure the distance.
Being drug to a local concert tonight, so i may be out of luck again tonight . . .I just wana see the New's Year's fireworks on a big screen this year!!!--gotta please the gf though. Funny-she wants to go to the concert, but also wants me to finish the projector . . .men, do you ever feel you can't win?! LOL!!

BTW-the fresnels not being cut to the exact size of the screen is ok, right? My screen is 3x4 and my fresnels are 5x7-i think, but the are centered, so that shouldn't matter; i believe.

no, no problem as long as they are centered...

Not the same size is fine as long as not the same size is bigger and centered

I only got about 1/2hr with the projector lastnight, b ut i moved the light. As i moved it back; the tunnel point was getting dimmer, but still a little noticeable. In turn; the whole picture was visible, but i would say it is dark. I will keep trying and when i think i have it right; i will install a reflector to brighten it up. I did find some fresnels that are a 4" FL, but they are only 3"x3". I would need atleast a 3x4 to cover the screen, right?
Thanks all!

why would you want 4" FL fresnels in the first place? if you need one in fornt to match your triplet thats one think, but I think for the rear you want one about 160 - 200 mm at most FL(4" is a bit too close to the bulb I think) and yes, they have to cover the entire screen(at least)..have you loked at other psone plogs here? theres all kinds of options for smaller pjs(shorter rear fresnel, pre-condenser...)

Hi I need some help with my projector. I have been doing research on the LL site and I'm not coming up with solid answers. I want to have the projector overhead so it wont be blocking my view or hitting my head on it. The pic below shows the projector at 15 degree angle. the projected image is not centered with the wall vertically I would like to lower that and raise the projector so its atleast 6 foot 2 inch off the ground.

I have learned that using to much keystoning will cause the bottom part of the screen to be magnified more than the top causing it to be out of focus. With 15 degrees of keystoning the top of the collector lens would be 20mm out from lcd cell and the bottom of the lens would be 120mm out from lcd. How many degrees of keystoning can I have an still have a fairly descent picture?

I have read some stuff about lens shifting. Not quite sure how that works? How many degrees of tilt will this give me?

If I could have the projector back farther possibly doubling the 6.5 feet in the drawing I wont have to keystone as much. So I was thinking of getting a long throw lens to make this possible. Here is a link to the one I'm considering. This one says it will work with my existing frenzels.

Long throw lense 135mm

I dont know how to plug this into the focal calc program to see how the distance will change from 6.5 feet.
since it says you can use the same frenzels from LL

Specifications

* Inner lens diameter: ~135mm
* Rear Focal Length (actual): 384mm
* Overall Focal Length (effective): 455mm
* Barrel Length: 159mm

If you have a better suggection for long throw lens please let me know?

Please let me know what you think would be the best combination of keystoing, lens shifting, long throw or other options I don't know about. Sorry this reply is so long. Thanks for help!!!!

Click to view attachment

You didn't say what size LCD but putting the numbers into the focal calc program using 450 for the triplet FL it suggests a 9.75 foot throw for a 7 foot screen. From your diagram it looks like you would put the rear of the projector at 9 feet, but it should be 9 feet to the triplet, which should reduce you angle a bit.

There are several solutions to your problem.

Depending on how discernng your eyes are you can probably safely keystone up to around 20 degrees. Please note the word "depending" in that statement. the most discerning eyes want a keystone below 10 degrees, since they want full focus from edge to edge. I am happy with a 17 degree keystone. By the way, I don't think you can get corner to corner focus regardless of angle for the same reason that extreme keystoning unfocuses some of the edges. Light in the corners have to travel furthure to hit the screen than light in the middle. So you can focus on corners or middle. Most people prefer the middle, since that is where the image is.

One way for compensating for an extreme keystone is to also tilt your wall screen. Let's say you need a keystone of 17 degrees to place your image in the middle of the wall, but want no more than about 15 degrees. Then you can angle your projector down 17 degrees and angle your wall screen up about 2 degrees. The 2 degrees is not at all noticable to th viewer, but the focus will be better. Your total keystone relative to the wallscreen is 15 degrees, but your projector will be angled at 17 degrees to position your image where you want it. I can safely say that depending on your viewing distance a screen tilt is not noticable up to around 4 -5 degrees.

If you build in the ability to slightly tilt your triplet this will also help. I find that a 1-2 degree tilt in the triplet will bring more of the outside edges in focus.

If you build in a slightly tilted lcd then this may also help. However, many lcds will start to become darker as you tilt them, so there is a tradeoff in this respect.

And finally, if you build a black border around your wall screen then you can have a slight trapazoid image extend into the black border. The viewing image will still look square because the black border simply cuts off the trapezoid protion.

The method I am currently using is all of these.

Thanks for the help Pagercam and phutton! One more question about the focal calc program. The picture of the projector projecting an image on the wall where you can input screen size. It looks like this is the measurement of the height of the screen right? Or is screen size assumed and always measured diagnally?
Thanks!

If you input the LCD diagonal you get the screen diagonal, vert -> vert, horiz -> horiz. Its what ever you want it to be just ned sto be the same on both ends

Thanks Pagercam for your help! I plugged the new info into the focal calc, 15 inch diagonal lcd screen and 120 inch diagonal screen using unsplit optics. The distance from triplet to screen 9.4 feet. I wont need the long throw lens now.
Curious I decided to use lcd height and screen height. The lcd is 12 inches wide and 9 inches high. I plug this in 9 inch lcd height , 84 inch screen height and I get 10.8 feet from triplet to screen. The image must show up as a rectangle on the screen rather than square?


My Plog

Sorry if this aint the right place.

I am in India and cant get a FS mirror. Can I use a normal Glass mirror with back side coating? Will it totally ruin the image?

Considering simple Vertical Fold.

It shouldn't look quite as good but it's worth a try. Others have reported acceptable results with a rear surface mirror. elken2004 has documented a method for stripping a common mirror to turn it into a FS mirror so search his posts/plog.

Thanks a lot. I am going to browse his Plog now.