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New lens underway

post #1 of 14
1/9/08 at 7:18pm
Thread Starter 
Well,

I have finally begun work on my new DIY anamorphic lens. I did some testing tonight on my living room wall and I was impressed. Had some focus issues at the extremities of the image but I think a curved screen would fix the issue. No pics yet tonight but I will take some tomorrow and post. Man I had no idea that a 120" scope screen was that much more than a 16:9 screen. My boys are happy, I'm happy, and my wife, most importantly, is happy. Got to love that.

Keep an eye out for pics tomorrow.

John
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post #2 of 14
1/10/08 at 9:54am
Thread Starter 
OK, here is a questions regarding my lens setup. When setting up the lens I built a temporary box about 8"x8"x5" for my 5x7 wedges. Once I get them set up inside the box and adjusted they overhang the edges of the box by about 1" on either end. I set them up with the long side of the 90 degree to the inside, small tip to the rear of the lens housing, similar to what Mark (CAVX) had on his website. Would changing the orientation of the lenses make a difference in how the image stretches? Here is an image.



Which was is correct? Comments are appreciated.

John
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post #3 of 14
1/14/08 at 6:19pm
Thread Starter 
Well,

Here are a couple photos of my DIY anamorphic lens in progress. I still have not decided on going 2.35 yet so I purchased a couple prisms and thought I would give a DIY lens a try to see how I like it. Mind you, I am still projeting on my living room wall (dark beige) right now since the basement is not in any condition for equipment. The lens is just mocked up in front of the PJ for now.

My lens is still a work in progress. I made the initial housing before I mocked up the prisms so it is shorter than it need to be. Once I am satisfied with the overall geometry I will make a final housing out of 3/4" MDF and finish it nicely. The prisms are 5"x7" optical crystal from a local supplier.

Here is a shot of the front of the lens


From the side


A screen shot


Sorry the pics are dark. I did not feel like getting the tripod out. Looks good so far. Even with SD DVDs with no upscaling, which is what is shown here. Some pincushion and keystone issues visible but with a mockup not bad at all. Once I get it in place permanently it may go away since my throw will be 17'. Screen shot is only 8' wide. My final screen will be 9'-6".

Let me know what you think. Total cost so far. $97
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post #4 of 14
1/14/08 at 7:23pm
Quote:
Originally Posted by John Martin View Post

Which was is correct? Comments are appreciated.

Your images look quite good John.

Whilst I have always placed the right angles in, I did so to ensure that the largest faces of thje prisms were out. If your prisms were the same angle, but did not have a right angle at the base, it would still work as it is the angle between the two faces and then the angle between the two prisms that produce the stretch...

Mark
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post #5 of 14
1/15/08 at 5:08am
Thread Starter 
Quote:
Originally Posted by CAVX View Post

Your images look quite good John.

Whilst I have always placed the right angles in, I did so to ensure that the largest faces of thje prisms were out. If your prisms were the same angle, but did not have a right angle at the base, it would still work as it is the angle between the two faces and then the angle between the two prisms that produce the stretch...

Mark

Thanks Mark. The prisms are oriented so that the long face is out. They both have a right angle on the interior. I assumed the way I had it was correct but it is nice to know for sure. This is only a temporary measure until I can afford to get an aftermarket lens but is definitely good enough for now.

Tonight I am possibly going to cut a new housing since I have no desire to mud sheetrock tonight. I need to pick up some thin black foam to support the prisms as well and some self adhesive felt for the ends of the prisms and the back of the lens. It is amazing how many other reflections you can get with this thing that you need to control.

John
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post #6 of 14
1/15/08 at 12:36pm
I also oriented the prisms so that the largest faces are on the outside. I think there might be some small distortions that vary in location from prism to prism. By orienting the prisms different ways you might minimize be able to minimize an artifact that you see in your image. I would start with the largest faces out. Then if I saw an artifact I might try a different arrangement of the prisms.

Randy
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post #7 of 14
1/15/08 at 1:07pm
John:

I orient my prisms with largest face outwards. I don't think it matters, though. The amount of glass, and the angles are basically the same. You may have to adjust the ultimate placement of the prisms themselves to get the right picture, however, because the angle of the faces relative to the lightsource beam will be slightly different.

That housing looks heavy! I picked up some 1/4 inch maple boards from the local hardware store and it works great! Much thinner walls and much lighter housing. Also, look in the heating/air conditioning section for some foam filter to use to hold those prisms in place.

One more thing. I used black paint (in those small bottles) mixed with some starch to really get an inky flat black and painted the ends of the prisms. Eliminates those nasty reflections really well. The paint doesn't adhere perfectly to the glass, so it will scrape off easily.

Good job! Your pictures looks great!
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post #8 of 14
1/16/08 at 12:57pm
Thread Starter 
Quote:
Originally Posted by RandyFreeman View Post

I also oriented the prisms so that the largest faces are on the outside. I think there might be some small distortions that vary in location from prism to prism. By orienting the prisms different ways you might minimize be able to minimize an artifact that you see in your image. I would start with the largest faces out. Then if I saw an artifact I might try a different arrangement of the prisms.

Randy

Randy,

I think having the long side out is working well and have really noticed any artifacts. I will look harder once I get my housing re-built.

John
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post #9 of 14
1/16/08 at 1:05pm
Thread Starter 
Quote:
Originally Posted by Steve Scherrer View Post

John:

I orient my prisms with largest face outwards. I don't think it matters, though. The amount of glass, and the angles are basically the same. You may have to adjust the ultimate placement of the prisms themselves to get the right picture, however, because the angle of the faces relative to the lightsource beam will be slightly different.

That housing looks heavy! I picked up some 1/4 inch maple boards from the local hardware store and it works great! Much thinner walls and much lighter housing. Also, look in the heating/air conditioning section for some foam filter to use to hold those prisms in place.

One more thing. I used black paint (in those small bottles) mixed with some starch to really get an inky flat black and painted the ends of the prisms. Eliminates those nasty reflections really well. The paint doesn't adhere perfectly to the glass, so it will scrape off easily.

Good job! Your pictures looks great!

Steve,

Yes the housing is heavy because 3/4" ply is all I had on hand and I wanted to mock something up one evening and did not feel like going to pick any smaller stuff up. I will probably go with 1/4" oak for the finished product. Not sure how I will brad nail that thin of material together. Guess 1" brads will be a bit too long so I ought to pick up some shorter ones.

Good idea about the paint on the ends. I was planning on electrical tape but paint is better. I will probably make a font and back for the housing with openings just big enough to get the beam in and back out as well. I think it would make for a more finished look with the whole lens enclosed.

I have also been using the PJ for outdoor movies like you do and now I am going to need to make a new screen that is scope. I have been using a plain painters tarp (beige) and make resort to getting something white and larger. I am hoping for about 16' wide. My wife will flip once she sees that go up LOL

John
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post #10 of 14
1/21/08 at 9:15am
Awesome, John. Good luck.

You're right about the 16 foot image. We do movie nights for the neighborhood, and new people are blown away by the set up and image (and I am using a pretty cheap projector!)

Sorry to go off topic, but I am trying to consider a better outdoor screen setup. I was considering taking heavy 4x8 insulation boards from home depot (fairly light, but also fairly rigid), paint them white, and get them up so that the screen is in four sections that can (somewhat) easily removable and setup-able. Not as storable as the roll-up canvas that I use right now, but I could then paint a black border around it in scope format.
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post #11 of 14
1/24/08 at 12:55pm
On my last lens I used Krylon flat black spray paint for the inside of the housing. I used the same paint for all four edges of the prisms. It worked ok but didn't stick to the glass very well. I've thought about mixing lamp black into epoxy and using that. Does anyone know of a paint that will stick to the glass better?

Randy
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post #12 of 14
1/24/08 at 1:34pm
Thread Starter 
I thought about using a glass etchant on the ends to rough up the ends and a paint like Tamiya RC Car paint made for flexible plastic car bodies. Sticks well and have a roughed up surface make make it even better.

John
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post #13 of 14
1/26/08 at 3:58am
Looking nice John. I may have to come down and see this when you have it complete. I will be watching this thread for sure. Like you I may go the DIY route until I can afford a better solution unless Mark gets the MKIII out soon.

Bob
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post #14 of 14
3/22/08 at 7:30pm
Thread Starter 
Bob,

I can mock it up temporarilty and bring it to the meet if you would like me to.

John
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