Now that I have used the OHP / LCD Panel for a while, I'm starting to notice some room for improvement. One thing that is particulary irritating is that near the top of the image, the light from the OVH projector seems to wash out the image. This is most visible during very dark scenes. The test image from the LCD panel looks fine so I assume it is the OVH and not the panel. If anybody has advice on how to get rid of this effect, I'd be very happy.
PS: One thing that is great with the newer DVD players is that they switch between PAL or NTSC output (bought a new DVD player for $75 US from Walmart). The Proxima LCD panel switches to PAL as well automatically so it gives a much better output then NTSC is capable of.
Mathieu
PS: One thing that is great with the newer DVD players is that they switch between PAL or NTSC output (bought a new DVD player for $75 US from Walmart). The Proxima LCD panel switches to PAL as well automatically so it gives a much better output then NTSC is capable of.
Mathieu
What OHP are you using? I'm currently experience the same problem, and I agree so far - I think it's all about the OHP.
A drawback of the OHP is that more light passes through the center of the stage glass than on the edges, and even less light gets through on the corners.
What you have is a semi-round bright spot right in the center of the stage. You might have your letterbox image slightly lower or higher than the bright spot, causing either the top or bottom of your image to be brighter. You have to find the spot that looks best to you overall.
I'm using a Buhl 2900... seems adequate for the job... my only complaint is the bright spots. I've heard a lot of talk on here (most of which I don't understand) about the quality of the optics, or lack thereof, on various OHPs.
I'm getting a Dukane 680 today, which seems to be everyone's favorite. Hopefully it will have better optics than the Buhl and my bright spot problems will be reduced or eliminated.
A drawback of the OHP is that more light passes through the center of the stage glass than on the edges, and even less light gets through on the corners.
What you have is a semi-round bright spot right in the center of the stage. You might have your letterbox image slightly lower or higher than the bright spot, causing either the top or bottom of your image to be brighter. You have to find the spot that looks best to you overall.
I'm using a Buhl 2900... seems adequate for the job... my only complaint is the bright spots. I've heard a lot of talk on here (most of which I don't understand) about the quality of the optics, or lack thereof, on various OHPs.
I'm getting a Dukane 680 today, which seems to be everyone's favorite. Hopefully it will have better optics than the Buhl and my bright spot problems will be reduced or eliminated.
Thanks for the quick feedback. I would be interested to hear if changing the OHP decreases this problem.
Just to link this post to another question I asked this morning, could you tell me how you connect your DVD (I assume this is what you use) to the panel? I'm using s-video which creates the problem with macrovison.
Regards,
Mathieu
Just to link this post to another question I asked this morning, could you tell me how you connect your DVD (I assume this is what you use) to the panel? I'm using s-video which creates the problem with macrovison.
Regards,
Mathieu
Even if you have a macrovision free panel (2 of mine seem to be MV free), you're most likely doomed to experience poor results going straight in through s-video.
You'll get a much better picture if you use a line-doubler to convert your s-video to VGA first, and it will eliminate MV.
What panel are you using? I've used the following line doublers with my panels: TV-4000 (XGA Theater), Viewsonic NextVision 5, Viewsonic VB50HRTV. They're all around $100.
You'll get a much better picture if you use a line-doubler to convert your s-video to VGA first, and it will eliminate MV.
What panel are you using? I've used the following line doublers with my panels: TV-4000 (XGA Theater), Viewsonic NextVision 5, Viewsonic VB50HRTV. They're all around $100.
The panel I use is a Proxima Ovation 822C which supports S-Video at 2 Million colors. If I switch to VGA, would the picture quality not get worse because the panel supports upto 640x480 resolution at less colors for PC input (it's not a lcd PC monitor)?
Mathieu
Mathieu
Well I've gone ahead and ordered the TV-3000 line doubler. The TV-4000 looks good but my panel only supports VGA so no need to go higher. Curious how it will turn out.
Good easter to all posters!
Good easter to all posters!
r3500vdp said:
I think the panel just does 2 million colors, period. I don't think it's different based on what input you use.
S-video is an analog input anyway - you can think of that input as having "infinite" colors if you like. The panel takes those analog signals and demodulates them into a palette of 2 million colors. If you're sending it 16M or 24M colors over VGA, I believe it rounds each color value to its nearest neighbor in the 2M set.
Anyone feel free to jump in and correct me if I'm wrong!
r3500vdp said:
Well, I got my Dukane 680 set up working last night. The lamp timer reads only 99 hour out of 750 average hours... but the bulb looks all cloudy and murky. Strange.
Anyhow, the way it stands, it *is* brighter than the Buhl 2900, but I wouldn't say it's eye-poppingly brighter. I only paid $30-$40 more for the Dukane than I did for the Buhl, so I'm happy with what few improvements I'm getting.
If there are indeed 650 hours of life left in the bulb, then I'd say I got a good deal.... if the bulb is on its last legs, then I'd say I got a little ripped. (These bulbs sell between $82-$150)
About the bright spots... the problem is very similar to the way it was before, but maybe just a little bit better. It seems this is something us OHP/Panel users are just going to have to deal with.
Anyone have any clever solutions for this "bright spot" issue?
I've thought of using a transparency on top of the panel, with a negative image of the bright spot... to darken out the bright spot(s) a little bit, evening them up with the rest of the image. It would be tricky to get it to match just right, and you'd have to be able to do a high quality, full grayscale or duotone transfer to film (at Kinko's?) Anyone know if this could be done?
Any other ideas?
Similar idea - I just had this one and it would be easy and cheap to try!
How about layering some transparent tape on the OHP stage glass?
One piece of tape would be nearly transparent... add another, or two, or three... you get the idea.
You could build up your gradient of tape to reduce the amount of light hitting the top of your image, or the bottom, whereever it is.
If you don't want to get sticky tape glue all over your stage glass, maybe use a blank transparency and stick the tape to that instead?
How about layering some transparent tape on the OHP stage glass?
One piece of tape would be nearly transparent... add another, or two, or three... you get the idea.
You could build up your gradient of tape to reduce the amount of light hitting the top of your image, or the bottom, whereever it is.
If you don't want to get sticky tape glue all over your stage glass, maybe use a blank transparency and stick the tape to that instead?
about the image being "washed out" towards the top especially w/ dark scenes, i have the same exact problem. i use an nec 1545v and a elmo hp-a305 sd. i have a theory as to why this happens. first, during bright scenes i can't notice this problem at all. my screen is positioned only 4 inches from my ceiling so my theory is that the ambient light reflecting off the ceiling is actually washing out the image as it hits the screen again since it's so close. i haven't tested this theory yet because i need to find something that i can temporarily tack to the ceiling to see if it eliminates that effect. let me know of your screen position and if you can verify this theory.
Have you checked if your panel is sitting on the OHP with a
slight incline? I noticed my SHARP QA-1200 had these rubber
pads underneath the panel, to keep it off the glass.
On the "south" end of the panel, the rubber pads where about
twice as thick as the "north" end rubber pads.. I have no
idea why they made them this way - this panel is completely new,
and the pads came with the panel from the factory. It also
seems to make an un-even sharpness of the picture.
I decided to try and lift
the north side up a few centimeters to match the height of the
south side, and when I did this, I noticed that the top part of my picture had a more even brightness to it when compared to the bottom.
I have actually added some extra rubber pad layers that I got
from another peice of furniture that I bought, and now the "top
brightness problem" is much less noticeable.. In fact, I may
try lifting it a wee bit higher to get it even more even later.
Check it out, maybe your panels are the same way..
slight incline? I noticed my SHARP QA-1200 had these rubber
pads underneath the panel, to keep it off the glass.
On the "south" end of the panel, the rubber pads where about
twice as thick as the "north" end rubber pads.. I have no
idea why they made them this way - this panel is completely new,
and the pads came with the panel from the factory. It also
seems to make an un-even sharpness of the picture.
I decided to try and lift
the north side up a few centimeters to match the height of the
south side, and when I did this, I noticed that the top part of my picture had a more even brightness to it when compared to the bottom.
I have actually added some extra rubber pad layers that I got
from another peice of furniture that I bought, and now the "top
brightness problem" is much less noticeable.. In fact, I may
try lifting it a wee bit higher to get it even more even later.
Check it out, maybe your panels are the same way..
Kl899, you are right - that will make it go out of focus.
Also, the reason either the top or bottom of the image is brighter is because that's the part of the image you have closer to the center of the stage glass - period.
The light source is much closer to the center of the stage glass than the sides or the corners.
Lifting the panel won't help, and it has nothing to do with the color of the walls, or whatever.
I just might try to print my test transparency at kinko's right now before I go and rent a movie...
Schmanthony
Also, the reason either the top or bottom of the image is brighter is because that's the part of the image you have closer to the center of the stage glass - period.
The light source is much closer to the center of the stage glass than the sides or the corners.
Lifting the panel won't help, and it has nothing to do with the color of the walls, or whatever.
I just might try to print my test transparency at kinko's right now before I go and rent a movie...
Schmanthony
I'm just speaking from my experience.
My panel was sitting on the OHP with a slight incline
because of the rubber pads being uneven in height.
This incline caused the top part of my screen to be
brighter and out of focus compared to the bottom part.
When I fixed height of the shorter pads, the uneven
brightness was fixed and the sharpness was now perfectly even
over the whole panel picture.
This made a big difference.. The way your panel sits
on your OHP can make for a big difference!
If your panels are sitting flat on top of the OHP, with
no incline, then you are having other problems (ie OHP)
IMHO... I just found the cause of my problem and fixed it.
My panel was sitting on the OHP with a slight incline
because of the rubber pads being uneven in height.
This incline caused the top part of my screen to be
brighter and out of focus compared to the bottom part.
When I fixed height of the shorter pads, the uneven
brightness was fixed and the sharpness was now perfectly even
over the whole panel picture.
This made a big difference.. The way your panel sits
on your OHP can make for a big difference!
If your panels are sitting flat on top of the OHP, with
no incline, then you are having other problems (ie OHP)
IMHO... I just found the cause of my problem and fixed it.
Make that panel sit flat - absolutely... but that is not the source of the OHP/panel bright spot problem.
Less scrutinizing viewers may never have noticed the effect - but I suspect this is a problem with *all* OHPs. You will notice it the most in a very dark scene, or a perfectly "black" picture, if you can generate that on your panel.
I tried printing out a few gray "clouds" on transparencies - and with fairly decent first-run results.
It will take many attempts to get the shape of the clouds to match the bright spots on the OHP just right, and I'll ultimately need a higher quality printer than the one they had at Kinko's.
I think this idea could work.
Less scrutinizing viewers may never have noticed the effect - but I suspect this is a problem with *all* OHPs. You will notice it the most in a very dark scene, or a perfectly "black" picture, if you can generate that on your panel.
I tried printing out a few gray "clouds" on transparencies - and with fairly decent first-run results.
It will take many attempts to get the shape of the clouds to match the bright spots on the OHP just right, and I'll ultimately need a higher quality printer than the one they had at Kinko's.
I think this idea could work.
I have an elmo 305sd, and i have the the same problem.
The problem is deffinatly the fresnel lens on my OHP. The elmo sd comes with a plastic fresnel, that seems to warp easily. I have taken the fresnel out and placed it directly under my panel so i could move it around with the OHP and panel running. In doing so, i was able to put the brightest point directly in teh middle of my screen. But it still was not perfect. I am now thinking I may need to replace my fresnel, preferibly with a glass fresnel. Now i am in search of a glass fresnel that will fit the Elmo 305sd. I may try that transparency thing out, to balance out the brightness, untill i am able to get a new fresnel.
The problem is deffinatly the fresnel lens on my OHP. The elmo sd comes with a plastic fresnel, that seems to warp easily. I have taken the fresnel out and placed it directly under my panel so i could move it around with the OHP and panel running. In doing so, i was able to put the brightest point directly in teh middle of my screen. But it still was not perfect. I am now thinking I may need to replace my fresnel, preferibly with a glass fresnel. Now i am in search of a glass fresnel that will fit the Elmo 305sd. I may try that transparency thing out, to balance out the brightness, untill i am able to get a new fresnel.
Just realize it's going to take a lot of trial and error. And maybe some exploration of the various print shops in your area to find out who will give the best quality output on transparency film for the cost. (I doubt it will be Kinko's... my efforts there were more or less a proof of concept.)
I made my transparencies in Adobe Illustrator and output it to Kinko's KDF format. Start with the center of your dark spot at about 75% grey. I know that looks dark but it turned out about right by the time it got to the film (That bit of advice should save you $2-$3 in copies right there!)
I've included an image of the kind of image I'm talking about. Just think of it as a starting point. What you want is basically a negative of the image you see on your screen when you project pure black through your panel.
I made my transparencies in Adobe Illustrator and output it to Kinko's KDF format. Start with the center of your dark spot at about 75% grey. I know that looks dark but it turned out about right by the time it got to the film (That bit of advice should save you $2-$3 in copies right there!)
I've included an image of the kind of image I'm talking about. Just think of it as a starting point. What you want is basically a negative of the image you see on your screen when you project pure black through your panel.
Attachments
I have this problem too !!
Hi All,
I've just found this thread, and i'm suffering from this problem too.
My spec:
Ask Impact24 LCD Panel
400w OHP
Sony DVD Player connected via s-video (Well until i get my HTPC sorted out !!
😉 )
Thanks Schmanthony for the pic, could i print this image onto a clear transparancy using my Epson 740 inkjet printer ??
If this works, it'll be well cool, as i've only had this OHP for about a week now, and the bright dot in the center of the screen has been bugging me, so i was happy to find out it wasn't just me suffering from this problem !!
Mentions of a glass fresnel to replace the plastic one used in most OHP's, mine also !! Where could i buy a glass fresnel in the UK and how much ?? And would it solve my bright spot problem ??
Many thanks for you help
Cheers
Cosmic023
Hi All,
I've just found this thread, and i'm suffering from this problem too.
My spec:
Ask Impact24 LCD Panel
400w OHP
Sony DVD Player connected via s-video (Well until i get my HTPC sorted out !!
😉 )
Thanks Schmanthony for the pic, could i print this image onto a clear transparancy using my Epson 740 inkjet printer ??
If this works, it'll be well cool, as i've only had this OHP for about a week now, and the bright dot in the center of the screen has been bugging me, so i was happy to find out it wasn't just me suffering from this problem !!
Mentions of a glass fresnel to replace the plastic one used in most OHP's, mine also !! Where could i buy a glass fresnel in the UK and how much ?? And would it solve my bright spot problem ??
Many thanks for you help
Cheers
Cosmic023
That pic that you included isn't what my problem looks like. It's more of a rectangular area right at the top.
Don't actually use that JPG I posted - you need something that's a lot higher resolution.
I used an illustrator file printed to a KDF at 600 dpi. You could also use Corel Draw. Make a circle or ellipse with a radial gradient from about 75% grey to pure white.
I'm thinking of continuing to use Kinko's for the trials necessary to arrive at the correct image... then I'll go to a print shop and print it out using a higher quality transfer process.
The picture I posted is just an example of what the image should look like.
I don't know if changing the fresnel is the way to go - it might have some effect on the bright areas, but I doubt it will significantly reduce the problem.
I'll bet *everyone* with a panel and an OHP has this problem - but maybe not everyone realizes it... maybe it's better to let them all live in their little happy bubble of denial - LOL.
To me, this problem is kind of a "showstopper" - making me seriously consider selling all my equipment and buying a retail projector.
I don't mind that the "black" in an outer space scene isn't totally dark black.. but the unevenness of those bright spots is really troubling.
I used an illustrator file printed to a KDF at 600 dpi. You could also use Corel Draw. Make a circle or ellipse with a radial gradient from about 75% grey to pure white.
I'm thinking of continuing to use Kinko's for the trials necessary to arrive at the correct image... then I'll go to a print shop and print it out using a higher quality transfer process.
The picture I posted is just an example of what the image should look like.
I don't know if changing the fresnel is the way to go - it might have some effect on the bright areas, but I doubt it will significantly reduce the problem.
I'll bet *everyone* with a panel and an OHP has this problem - but maybe not everyone realizes it... maybe it's better to let them all live in their little happy bubble of denial - LOL.
To me, this problem is kind of a "showstopper" - making me seriously consider selling all my equipment and buying a retail projector.
I don't mind that the "black" in an outer space scene isn't totally dark black.. but the unevenness of those bright spots is really troubling.
- Status
- Not open for further replies.