Problems with bleeding!

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Inferno Acid

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Joined 2006
#1
Hey guys! Great to be here ^_^
Anyway i to am starting with a simple Overhead projector + old tft screen beamer project. And i managed to get a free projector and TFT screen, but the projector has a seveeeere case of color bleeding. i can focus the center just fine but the sides are Red/Blue fuzzy, and not just a little. So if i place the TFT monitor over it i'll probably will only be able to see the center properly, which is not what i want 🙁
Any tips on how to tune it? Or is it just a case of a shitty projector and i should look into getting a new one?
The projector is an A+K Eurolux!
Oh and yes i did search around.. Damn popup 😛 I couldnt get any specific threads on Color Bleeding. Maybe there's another term for it which i didnt search for yet?
 
#2
An externally hosted image should be here but it was not working when we last tested it.


There's what it looks like. Sorry the pic is a liiiiittle out focus, trust me the ohp is focussed properly. I only had 10 seconds of batt life on the cam so i couldnt take a proper pic :

An externally hosted image should be here but it was not working when we last tested it.


And there's the projector. Fear. Its a single projection lense by the way
 
#4
Thanks for the reply, are you sure? and will any fresnel do? Because i can get one for 13 bucks locally here.
I heard the problems with cheap OHP's are the projector lenses. So i thought it would be the case here. Aparantly not 😀 So is there any quality diff with fresnels?
 
#6
okay thanks 😀 i'll take that in serious concideration, got any tips of where i could find the specs of the fresnel? the focal point of the projector lense is 270MM and its spherical if that matters, since i see your lense is flat.
Im still a big noob at this 🙂
Anyway i would love to see some other opinions of people in here 😀 Just to get it 100% confirmed before i start spending stuff.
 
#7
i dont blame you ...... i cant believe others havent commented ... i would try looking up replacement fresnel for whatever model OHP that is on google.. then check ebay .... also you said you fresnel is spherical? or you mean the lens ? my lens isnt flat .. just looks that way. anyways you should check out the forum at diyprojectorcompany to .. if you havent already 😀
 
#9
Hm. I got an image very similar to that when my projection lens (which was of too small of a diameter for my fresnel size) was a little bit off center. I could just get it to have the colors right (in other words, everything was the projected color, white), but moving it a couple of millimeters up, down, left, or right, would result in an image like that. I'm not saying that that's the problem you're having, but they're similar. If this IS the root of your problem, then maybe the column holding the mirror and pj lens is bent a bit? Also, just wondering, but is that pj lens the one that came with the OHP, or is it a different one?

Also, I want to call the problem that you're having "chromatic abberation", but I don't think that's correct. It seems to me that chromatic abberation is where blue shows up predominantly on one fringe, and red-yellow on the other, but maybe that and what you're experiencing are both chromatic abberation.

Sorry, this probably didn't help. 🙁
 
#10
thanks for the tip 😀. Man i wanna know what exactly is wrong with my damn ohp.. meh i might be able to trade this one in for another one and that time i'll check if it works properly.

Still, any advice of anyone else would be greatly appreciated, could save me some shizzling around ^_^
 
#11
dnsey said:
I suggest that you remove your Fresnel and inspect it. You will see if it's warped, and can easily measure the FL.
Click to expand...

I did, its not realy bent or anything it was a liiiiiiiiittle hollow but i take it thats normal?

milihpen said:
Hm. I got an image very similar to that when my projection lens (which was of too small of a diameter for my fresnel size) was a little bit off center. I could just get it to have the colors right (in other words, everything was the projected color, white), but moving it a couple of millimeters up, down, left, or right, would result in an image like that. I'm not saying that that's the problem you're having, but they're similar. If this IS the root of your problem, then maybe the column holding the mirror and pj lens is bent a bit? Also, just wondering, but is that pj lens the one that came with the OHP, or is it a different one?

Also, I want to call the problem that you're having "chromatic abberation", but I don't think that's correct. It seems to me that chromatic abberation is where blue shows up predominantly on one fringe, and red-yellow on the other, but maybe that and what you're experiencing are both chromatic abberation.

Sorry, this probably didn't help. 🙁
Click to expand...


Yes the lense thats on it is stock for that ohp 😀 I dont have the time to test it now but i will later today! It did help no worries 😀 We might rule off something now, or find the problem 😀
 
#12
Sorry for the double, no edit feature O_O
Anyway I checked the fresnel, and its kinda hollow, when i put it on a glass plate it stands up on the four edges. Is that normal? And is it supposed to be hollow? because if i gently ( i know that fresnels scratch fast ) push on both sides i can feel it bend in and the two sides touch eachother. I'd figure that a good fresnel is massive?
sorry if this is übernooby of me to ask 😉:hbeat:
 
#13
Inferno Acid said:

Anyway I checked the fresnel, and its kinda hollow, when i put it on a glass plate it stands up on the four edges. Is that normal? And is it supposed to be hollow?
Click to expand...

They're hollow because it is actually two fresnels with the edges glued together. The first fresnel is the collimator to redirect the light into a parallel beam the second is the collector to redirect the beam so that all the light goes in the projector lens. That’s where the split and unsplit talk comes from. In a split design, you actually cut the two fresnels apart and put the LCD in between them. In an unsplit design they leave the two fresnels glued together and put the LCD after them.

You could test to see if the bleeding is from the projector lens if you can remove it from the OHP. You could find or make a tube the same length as the focal length of the projector lens. Place the projector lens on one end and a flashlight on the other then focus it on the wall and see if the light from the flashlight bleeds around the edges. That would help narrow it down. Just an idea.

Zaner21
 
#14
zaner21 said:


They're hollow because it is actually two fresnels with the edges glued together. The first fresnel is the collimator to redirect the light into a parallel beam the second is the collector to redirect the beam so that all the light goes in the projector lens. That’s where the split and unsplit talk comes from. In a split design, you actually cut the two fresnels apart and put the LCD in between them. In an unsplit design they leave the two fresnels glued together and put the LCD after them.

You could test to see if the bleeding is from the projector lens if you can remove it from the OHP. You could find or make a tube the same length as the focal length of the projector lens. Place the projector lens on one end and a flashlight on the other then focus it on the wall and see if the light from the flashlight bleeds around the edges. That would help narrow it down. Just an idea.

Zaner21
Click to expand...

Ahhh 😀 Some one should realy make a thread with all those DIY basics summarized like that, there's one but those cover the realy basic basics.
Anyway thanks for that explaination.

Anyway guys i might be able to get another free OHP, and this time i get to choose one from about 20! This time i'll also pick one non halogen, metal halide its called i think? Anyway metal halide OHP's are supposed to be quite expensive i figure, pretty neat if i can get one for free ^_^

Thanks alot for the help though! But im giving up on this one. Why fix it if i can get a new proper one for free?
 
#15
Color tuning

Too bad you're giving up on this one.
I think that your problem is color tuning.

From looking at your picture, I think that the color tuning adjustment is at the front bottom of the OHP. Try working with that and see if it fixes your color fringe problem. The color tuning adjustment changes the distance from the lamp to the fresnel.

Here's why.

When the projection lens is moved closer to the stage to increase image magnification, the longer wavelength light rays are blocked by the entrance aperture of the projection lens. A "bluish" color then appears around the border of the projected image. When the projection lens is moved farther from the stage to decrease image magnification, the shorter wavelength light rays are blocked by the exit aperture of the projection lens. This causes a "reddish" color to appear around the border of the projected image.

This coloring effect is eliminated when the image of the lamp produced by the Fresnel lenses follows the movement of the projection lens. Movement of the lamp causes its image to move and is referred to as "color tuning".

Few Overhead projectors have automatic color tuning through mechanical linkages that adjust the distance of the lamp to the fresnel in relation to the position of the projection lens.

Look for "color tuning" dials or knobs on your OHP.

If someone notices a similar problem with their DIY projector, it might not be chromatic aberration from the lens, it might be a color tuning problem and adjusting the distance of your lamp to your fresnel might fix it.

TGreenwood
 
#17
Yeah ive been fiddling with that dial, it was all the way down at first, when i raised the lamp it only got worse and worse. So its on the lower most position atm. It would be so much easier if one of you guys could come over here and fix it for me 😉

When i get home im gonna give it one more shot! i'll check if there are any things that i overlooked inside the projector.
Thanks so far! 😀 😀
 
#18
Have you tried just moving the projector further away from or closer to the wall and refocusing? It might make the projection bigger than you want (or smaller), but might take care of the colors, since you have the color tuning as far as it will go.
 
#19
Hey guys i fixed the problem!... and... its not what you'd expect it to be... Dont get angry at me now 😉... The projector lense was on backwards... I flipped it over and the screen is perfect, on 100'' display i got 1 mm of bleeding on the edges, which isnt bad at all 😀 and i can fix that by re aligning the lense!!
I feel so stupid now :xeye:.. But meh, the guy who gave me the OHP said it went on like that so how should i know? 😛

Thanks for all the help though! 😀 IM SO HAPPY!

Edit: Woah i found the edit button!

Edit2: Thanks again all! 😀
 
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