DIY anamorphic lens

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#1,083
I only had one fall so far--I stood up and I hit it with my head

I think in order to secure mine, I'm going to cut a piece of plywood to fit inbetween the pieces I have for sides.... with a little bit of foam left over from building my speakers as a cushion, I think I can put a bit of compression on it to hold it in place, and still be able to move it slightly if I need to.

I have noticed that some pictures of the housings you guys have are open on one side... I'm still experiencing some unfortunate bending that I can't get rid of... would that in any ay help???

Ok Maybe I should go upstairs and get the Digital camera out and finally snap a few pictures
 
#1,084
Bud Bray said:

It's the reflection off 1 prism onto the other. These aren't anti-reflective coated like glasses. Don't think you can do much, do you have the inside housing blacked out?
Bud
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Hey that's cool Bud that you have worked what caused it. I was thinking more along the lines as off the screen to the front prism...

The worst thing to do it is that THX logo - all black screen and bright THX inthe middles causes a reflection off to the left hand side. Other then that very minimal and only as has been described...

artbypaul said:
Yep, everything is blacked out around the prisms. I guess it's not too bad, nobody has commented on it. It usually only lasts for a few seconds normally. But you're absolutely correct about not being a fixable problem as the image is obviously bounced off the facing prism sides which can't be covered.
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Check SW3 where Yoda and Anikin coverse about his dreams. That sceene is probably the worst offender in a film I have found. It was terrible with the water prisms, and just noticeable with the crystal prisms...

morkys said:
That's too bad. I wonder if it is possible to cost this glass with anti-reflective coating.
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Bud Bray said:
I think Mark looked into that. Considering the cost to coat a pair of glesses, this size may be REALLY expensive. Doesn't hurt to look around though.
Here's a question for people, how have you got your prisms in the housings? Are they secured? (So far i've broken 4 prism from having them fall out of my tilted housing, not secured in yet). I'm still fighting wether to have them fixed in place or rotating...
Thinking i'll go for FIXED for no(so more don't break) and retro-fit for pass thru later.

Bud
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I sure did, and it was very expensive to do - like into the thousdands...

Multi coating is way more complex then simply adding a spray pack type product to the surface...

Mark
 
#1,085
Mark Techer said:


Hey that's cool Bud that you have worked what caused it. I was thinking more along the lines as off the screen to the front prism...

Mark
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It can't be that since if it was, the front prism is angled so the reflection would be off to the RIGHT(depending how the prisms are aligned, mine are like yours) WAY off to the right. If you watch the light beam(off center so you don't blind yourself), you can see the images and where they reflect. Shine a flashlight at the front prism & see where the reflection goes...

Bud
 
#1,086
Bud Bray said:


It can't be that since if it was, the front prism is angled so the reflection would be off to the RIGHT(depending how the prisms are aligned, mine are like yours) WAY off to the right. If you watch the light beam(off center so you don't blind yourself), you can see the images and where they reflect. Shine a flashlight at the front prism & see where the reflection goes...

Bud
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Yeah, good points. I'll have to try the flash light test...

My reflections (the few I see) are off to the left, and are only visible between the hard left and the left 3rd of the screen. I don't have them any further right than that.

I watched Minority Report tonight which has that real contrast of bright and dark scenes, so a few did show up. They appear as a slight green mark than may blend into the surrounding picture depending on what is on screen at the time.

Oh well, you can't have perfection for what these prisms cost...

Mark
 
#1,090
I think you want the anti-reflection/polarizer after the last stage of prisms/lens because otherwise, there is no garantee that some stray reflection is somehow getting through. Plus its easier to simply add it at the end and allow for you to keep whatever fixed or adjustable prism configuration you already have. It could work between prisms, but you'd have to figure out between which prisms, the individual paired up? Between the sets of prisms or what? May as well just do it at the end of the chain, although you can always try different locations. It's just a thought. I figure if a polarizer can reject reflections from the surface of water and windows when taking photo's, it make work ok in this application too. As usual, one never knows until it's tried out.

Anybody have a clue where we could find a polarized and anti-reflective coated peice of glass not too much bigger than one of these prisms that won't otherwise negatively affect the image or drop lumens too much?
 
#1,091
morkys said:
What about placing a final sheet of anti-refective and polarized glass after the prisms/lens?
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Now I did try this in front of the front prisms which reduced these unwanted reflections by at least a further 30%, meaning that only the very worst (say the THX logo for example) reflections were visible. It adds a lot of extra weight to the lens though for some, but not a total fix...

Bud Bray said:
I was thinking between the prisms...
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The pieces of anti-reflective glass I had samples of were just too big to go inbetween the prisms, but given that I was still thinking about reflections being from the screen, this is worth persuing once again...

morkys said:
I think you want the anti-reflection/polarizer after the last stage of prisms/lens because otherwise, there is no garantee that some stray reflection is somehow getting through. Plus its easier to simply add it at the end and allow for you to keep whatever fixed or adjustable prism configuration you already have. It could work between prisms, but you'd have to figure out between which prisms, the individual paired up? Between the sets of prisms or what? May as well just do it at the end of the chain, although you can always try different locations. It's just a thought. I figure if a polarizer can reject reflections from the surface of water and windows when taking photo's, it make work ok in this application too. As usual, one never knows until it's tried out.
Click to expand...

I would think that you might bond the anti-reflective glass to one of the prisms - even using small dabs of hot glue from a hot glue gun to hold them in place. That way you align the prisms, you also position the A-R glass...

morkys said:
Anybody have a clue where we could find a polarized and anti-reflective coated peice of glass not too much bigger than one of these prisms that won't otherwise negatively affect the image or drop lumens too much?
Click to expand...

I used a product (but ditched the samples when I moved 🙁 ) called "clear view" which is a laminated glass product - glass/plastic/glass. It has just 9% (?) reflectivity instead of the usual 20% of standard glass.

What I want to know is that if they can coat full sheets of glass, then why can thy not coat our prisms with the same stuff?

Also because the glass is a different product to that of the prisms, it might be the achromatic solution we really need as well...

Mark
 
#1,095
reflections from lens?

It was brought up recently about unwanted reflections from the prisms, where Bud Bray seems to have identifed the problem as stray light between the prisms that then hits the screen.

We agreed that the worse case senario might be a black screen with bright images such as the THX logo or maybe some text, but check these out...

DSCF5550.jpg

DSCF5549.jpg

DSCF5547.jpg


With the exception of the small "light smear" near the T, note there are no green streaks 🙂

Mark
 
#1,096
Awesome Mark! Great looking shots!

I readjusted my lenses and made sure they were basically touching and centered with lens to get the proper geometry on the screen and I'm no longer really seeing much stray reflecting on the image.

What I don't understand is how RANDOM it is... Often times scenes that should show the annoying reflections show absolutely nothing, then later in the film the same lighting situation occurs (dark scene with a small brightly lit object on the right side of the screen) and it shows as a reflection!

It's almost like these prisms are mocking me! Like they're saying, "Remember, this is home made! " LOL! Or maybe more appropriately, "Don't be so proud of this technological terror you've created..."
 
#1,097
Thanks for the feedback, here and AVS 🙂

Yeah it is strange alright. The other day, I had green streaks right across the screen that I have never seen before. I took out the lens, and re-installed it, and the streaks were gone. I can not explain that at all.

When I hand snapped these images this afternoon, I didn't even pause the disc, as I was hoping to capture some element of green streak, but nothing.

If you click on my web thing you can see my latest BLOG update which has a new CIH Explained section with photos...

Mark
 
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