DIY anamorphic lens

[Mark Techer]

No pix attached. Best to open a photobucket account and then use the image attach feature. That is how I went from thumbnails to full size images I attach now...

Mark

[sdspga]

Mark,

I know you can eyeball the angles and get them correct, but for those of us who are new to this game, can you give the angles of the glass prisms to give the 1.33 stretch.

Note, if you could give the angles relative to the flat bottom surface or the lens, I think my feeble mind could understand that. Thanks,

Scott

[mfeidler]

I live in the Houston, TX area and I found a Trophy shop that has them instock (Medium size) I will go buy tommorow and check them out. A simple drawing with angles written on would be great!

Thanks,
Mike

[Mark Techer]

Originally posted by sdspga
Mark,

I know you can eyeball the angles and get them correct, but for those of us who are new to this game, can you give the angles of the glass prisms to give the 1.33 stretch.

Note, if you could give the angles relative to the flat bottom surface or the lens, I think my feeble mind could understand that. Thanks,

Scott

The angles might vary due to the thickness (where mine are 2" or 50mm at the base), so would only be a guide if that...

TIP for 3 step alignment.

1. Place them together to form a solid block with the apexes opposed in front of your projector and align the rectangle of light so that you are flush top to bottom for the 16:9 area of the centre of the screen.

Table mounting might be the go here if your new to this. I recommend placing the 90degree sides in together so that you use the hypotinuse of the triangle (in plan) as the front and rear faces. It is the largest area, so will ensure the best results.

2. Then start by moving the thick end of the front prism out towards the screen. Your screen should be 2.37:1 BTW not 2.35:1. What you should see is the side that the prism in on should start to stretch, IE, I have my lens set up with the front prisms out on the left, and it controls the left side of my screen...

3. Now slowly bring the thin end of the rear prisms towards the projector. This prism will be on the right, and it will control the right hand side.

You are stretching the light beam, so you need a straight 16:9 image to start with first. If you have keystone or other errors including a non level image, the lens will only magnify the problems as it stretches the light...

There should be about (for mine anyway) 40 degrees bewteen the front and rear faces...but the ultimate test is projection onto the screen at 2.37:1...

Originally posted by mfeidler
I live in the Houston, TX area and I found a Trophy shop that has them instock (Medium size) I will go buy tommorow and check them out.

That is cool. Are they the same price as on the 'net?

Mark

[sdspga]

Thanks Mark. Through trial and error I have come up with my settings. A couple observations:

1) One can REALLY bend the light. Throwing from 14', I could get a 10' wide image with no problem and not much geometric distortion.

2) Too wide is a real concern. Had the wife come down to get her impressions. Was showing LOTR, Return of the King. During the final battle scene, her first comment was "I really like the wider, bigger screen" That soon turned to "I feel like I am in one of those IMAX theaters". After about 5 minutes she said "I feel dizzy. I'm going upstairs."

3) No detail was lost with these prisms. I fully agree that using the full panel enhances the PQ as well as brightness. Unbelievable picture!

While these prisms can make huge picture adjustments, finding a comfortable viewing size is still of primary concern. As I am viewing from 11', I think under 9' is the better size for me.

Finally, you are right in that you need an enclosed box for these prisms. While I taped the edges with black electrician's tape, I still had images on the left and rear walls. Actually the left side one scared the crap out of me during one of the battle scenes because we had all the lights off and I picked up movement in my peripheral vision

[Mark Techer]

Originally posted by sdspga
Thanks Mark. Through trial and error I have come up with my settings. A couple observations:

1) One can REALLY bend the light. Throwing from 14', I could get a 10' wide image with no problem and not much geometric distortion.

2) Too wide is a real concern. Had the wife come down to get her impressions. Was showing LOTR, Return of the King. During the final battle scene, her first comment was "I really like the wider, bigger screen" That soon turned to "I feel like I am in one of those IMAX theaters". After about 5 minutes she said "I feel dizzy. I'm going upstairs."

3) No detail was lost with these prisms. I fully agree that using the full panel enhances the PQ as well as brightness. Unbelievable picture!

While these prisms can make huge picture adjustments, finding a comfortable viewing size is still of primary concern. As I am viewing from 11', I think under 9' is the better size for me.

Finally, you are right in that you need an enclosed box for these prisms. While I taped the edges with black electrician's tape, I still had images on the left and rear walls. Actually the left side one scared the crap out of me during one of the battle scenes because we had all the lights off and I picked up movement in my peripheral vision

Yes I'm down to a 4" x 5" side reflection that I will fix by simply adding a piece of MDF to the base under the projector. Other then that, I have fixed all other problems with mine...

Viewing angles for cinema scope 2.37:1 video will differ slightly to what is excetable (or preferred) for 2.39:1 for film. Where film wants you at or closer than 36 degrees, I think video works the other way. You don't want to be closer then 36degrees at home given the source (DVD) is SD, not HD. HD DVD and or BrD might change this, but for right now, you want to be back a little more, or reduce your screen height which ultimately affects the width.

There is an exellent diagram for working out the best and worst seating locations which I am attaching HERE.

Right now I have an 8 foot wide screen and my back row is 1.54 time the screen width. The front row is 1.54 times the 1.78:1 screen width.

Soon I will have to reduce the image width to just 7 feet or mabe less when I move. Naturally, my screen height changes as well, but the point is, the viewing angle keeps the size of the angle constant relative to the seating distance (if that make any sense)...

So basically, I belive you should not be seated any closer than 1.54 times the screen width for a "scope' set up. If you are talking about 16:9, then work of the height and times that by 3.68.

When I design a room, I actualy take the room length and divide that by 2.17 first. This gives me the screen's width for that room based on SD video and this idea works really well. You may be surprised just how large a screen can still be.

Take the screen width and times that by 1.54 gives you a perfect 36 degree veiwing angle, as well as keeps your seats off the back wall, so make s your sound system work better too...

So back on topic, I am really glad that your lens is working out. Can you post some pix?

Mark

[Steve Scherrer]

Originally posted by sdspga
Actually the left side one scared the crap out of me during one of the battle scenes because we had all the lights off and I picked up movement in my peripheral vision

Maybe there's a market for this! Surround Video!

[Steve Scherrer]

(Sorry for the double post. This site has some weird edit rules...)

Incidentally, this project is driving me crazy! It couldn't have come at a worse time for me. I am working like crazy, then come home, spend some time with the kids, help put them to bed, then have about 1/2 hour to work on this thing. Needless to say, I am not getting very far.

But my second small wedge came in yesterday, so I was able to at least take my raw materials and start sizing things up. Everything should work out well, assuming I use the proper adhesive. My father actually stopped by last night for an hour or so, and he was very intrigued by the whole project. He's as cheap, if not cheaper than me, so when I showed him the prices on the Pr**sonic page for these things, he became especially interested.

[andy238]

Thanks for the 3-step program, Mark It will really help.

I just ordered my "trophies". As soon as I told her the sizes I wanted she knew I wanted them blank. I didn't even have to tell her! This is a gas... I can't wait to get the prisms after reading the latest posts.

If these work out this will have to be the find of the century.

sdspga, your wife's comments made me laugh out loud!

Andy

[Mark Techer]

Originally posted by andy238
If these work out this will have to be the find of the century.

They do and it is

This just goes to show how some think out side the square, again well done Steve and Fisher.

I spent most of the last year looking in optical stores, had found plenty of items made from the same crystal, but they were all cubes, or rectangular prisms, no wedges.

Found a manufacture of BK7 with optic coating which turned out to be more expensive than the ISCO III...

I would never have thought to try a trophy shop...

Mark