This is interesting. I've about all but cleaned up my CA problems. The last few times of lens placement (including just 5 min ago) has revealled no real problems. The placment gives uniform pincushion as well...
A soft dry cloth...
Mark
Steve Scherrer said:
Ya, I still have a bit of a bow at the bottom (ceiling mounted). I've found if you tilt the prism a bit, it squares up, Since you have the housing done, that would be a problem...I'm just going to do masking at the screen bottom, for the 1" height of the bow(center), i'm not going to go nuts worrying about it.
Interesting. I have seen Mark say this before, but I was unable to get the pincushioning out of the bottom of my screen no matter how much I tilted. Did you move both prisms, or just one?
If your getting barrel on just the top or just the bottom, you may need to bow that edge of the screen to compensate. Depending how your screen is made and mounted, if you can secure the centre and wedge out the ends a bit, you should be able to correct the barrel...
Mark
Mark
I'm a bit confused...
Are you guys stating that you are able to correct barrel or pincusion by tilting the prisms and or the total lens?
Mark
Are you guys stating that you are able to correct barrel or pincusion by tilting the prisms and or the total lens?
Mark
Mark Techer said:
Each prism. The prism sits perpendicular to the bottom of the housing, if you tilt the top of the prism away from the projector, it reduces the bow for that prism, do both and the bow is reduced. Tilt too much and it begins to bow the other way. Since my PJ is ceiling mount, the bow is along the bottom of the screen image. When I tilt the top of each prism while sitting in the housing, I can bring up the drooping corners on the bottom and get it pretty square. BUT, that's because I haven't yet secured the prisms in the housing with mounts. Unless I leave a bit of play, I will loose this ability. Try it. I just use a thin piece of cardboard right now as a wedge to test. I plan to have masking at the bottom which will hide and bottom bow.
Bud
That is pretty cool Bud.
My second set of prisms arrived and I was just playig to see if a 4 prism lens could work in the limited size that I have. So far yes, it looks promising.
The projector is back in its box for the move, so sorry no photos till maybe next week...
Mark
My second set of prisms arrived and I was just playig to see if a 4 prism lens could work in the limited size that I have. So far yes, it looks promising.
The projector is back in its box for the move, so sorry no photos till maybe next week...
Mark
Yes, before I had to pause this project, I was finding I could correct the bow on the bottom of my screen as well as a drooping corner on one side by tilting the prisms one way or the other. I found it is also hugely important to shoot the beam as squarely as possible at the screen. I noticed any left/right offset causes geometry problems in the corners. I am, like Bud, shooting from the ceiling thus have the bowing on the bottom.
Mark, I could have sworn you had mentioned that you tilted your entire lens housing to reduce these problems. Maybe I read that from someone else. I saw from your pics that you also curved your screen, but that really isn't an option for me in my setup.
I need to reassemble my prisms and try some more.
Scott
I am tilting my housing as well, but tilting the individual prisms slightly reduces the bow a bit more.sdspga said:
sdspga said:
I believe Mark did mention tilting the entire housing, but I am intrigued about tilting of the individual prisms. I believe I could probably easily work this type of feature in my housing. So instead of having the top post (which is threaded) go through a hole in the top of the housing, it would fit through a slot, so depending on how the housing is mounted, perhaps the image could be further dialed in based on tilt. Interesting...
That was back in the water prisms days, but I did that because they were (are) just 125mm (5") high, and with them being 30 degrees, the lens was long at over 250mm (10") and I would get vignetting if the lens was not tilted.
Later (when I started playing with resin prisms) I made a shelf system that allowed me to quickly interchange the prisms. I made the shelf 200mm (8") deep and high. I had to use a piece of 16mm MDF to raise the water prisms, but it fixed the vignetting issues, once I learned how to align the prisms better. I also found that slight over lap made the lens shorter.
But the curvature was still there, and the only way I have ever fixed that was to bend the screen (which at one stage was bent both in the H and V plains called the rouge torus). Since then I have removed the V bend and only kept the H bend. The bend is not much, about 40mm (less then 2") in total and there is more curve at the bottom than at the top, and it works for me.
The shelf system mount has been reworked and allows the new case of the "Aussiemorphic Lens" to sit in front of the projector...
Mark
Later (when I started playing with resin prisms) I made a shelf system that allowed me to quickly interchange the prisms. I made the shelf 200mm (8") deep and high. I had to use a piece of 16mm MDF to raise the water prisms, but it fixed the vignetting issues, once I learned how to align the prisms better. I also found that slight over lap made the lens shorter.
But the curvature was still there, and the only way I have ever fixed that was to bend the screen (which at one stage was bent both in the H and V plains called the rouge torus). Since then I have removed the V bend and only kept the H bend. The bend is not much, about 40mm (less then 2") in total and there is more curve at the bottom than at the top, and it works for me.
The shelf system mount has been reworked and allows the new case of the "Aussiemorphic Lens" to sit in front of the projector...
Mark
Hi guys, got the prisms mounted in the new housing, ROAR will be coming by to take some good pix, still doing the prism arrangement tests, post pix soon. One question tho, i'm noticing on a black background, when there is a bright text or shape, i'm getting some minor ghosting. Is more blocking on the prisms needed? Also, is painting the housing inside black a good idea or would it cut down the brightness?
Bud
Bud
Bud Bray said:
Say like the THX logo and you see a ghost to the left (based on the thick end on the left of the front prism)? The ghost is actually the only limitiation to using the trophies as they are not anti-reflection coated.
I experimented with a piece of anti-reflection glass, but it did not fix the ghost 100%, but it did reduce the bit of light reflection to virtually nothing.
Generally I am not seeing it though.
Painting the inside black will make thing better, but may not fix the ghosting. I think it has to so with angles.
I also played with a 4 prisms lens. Interesting effects, but not sure if I will upgrade just yet. I had to re-work the case, and change the angles, but I still need to do light tests which will be a while whilst I move...
BTW, these prisms are 1.7KG each, so a 4 prism lens is very heavy...
Mark
Well! I think we should petition the trophie places to produce trophies with anti-reflective coatings! We must make ourselves heard!We must take a stand against this injustice.....end of rant!
Oh well, small price to pay for the small price we did pay for these
Oh well, small price to pay for the small price we did pay for these
How much tinkering does it take to get good geometry and how is the chromatic aberation etc? I may still pick up a used Panamorph 752 or similar to get me going and have for comparison, but I ultimately want to make one of these things myself. I guess I need to just order the prisms. I need to know what sizes/shapes etc.
Bud,
Thanx for the information, I totally missed your posting it right away in your reply.
What size shape do I order?
Which projector are you using?
thanx,
😎
Bud,
Thanx for the information, I totally missed your posting it right away in your reply.
What size shape do I order?
Which projector are you using?
thanx,
😎
morkys said:
Hopefully this week I can put things back together (curtains,etc) then have people over. The size depends on your PJ...I'm using the mediums. I have the Optoma HD72. I hear the 70 is pretty kick *** and cheaper too...just my luck!
On a side note, I realised that different assemblies of the 2 prisms doesn't make a difference...the angles are always the same! AND I discovered my PJ was a bit crooked in the mounting so that's WHY my right side looked lower...cuz it WAS!
DOH!
Oops! sorry bout the 3-letter word...it was meant in a NICE way!