DIY anamorphic lens

[hoxford]

I thought I'd start an anamorphic lens topic for any AVS Forum members browsing around or anyone else interested in the topic.

First off, here's a link to Tor Arne's site describing in great detail his construction of an anamorphic lens (several actually):

http://home.c2i.net/ahustvedt/arnemorph/

For you German speakers, here's a link to the site that did the original R&D on the lens:
http://ww2.bepo.com/jochen/anamorph/

I think there's a link there to the German discussion forum where the original ideas were hashed out. Sorry, I don' t have it handy and don't speak German well enough to find it.

There's also some interesting info on prisms and anamorphic lenses here:

http://appft1.uspto.gov/netacgi/nph-...l&r=0&f=S&l=50

We've been moderated out of existence on the AVS Forums so I'm hoping some of the other 'rejects' from there will come over here and we can get a good discussion going.

[tahustvedt]

Hi, I will check back to this forum daily and hope there we get a lot of replies from AVSforum members.


Some notes.

-The lens works upside-down too, but this gives more lens-shift and more uneven focus.

-I will try to compensate for the barrel distortion in only one direction instead of both like I have with my previous models. The compensation gives some focus-drift towards the corners that I want to avoid. Compensating in one direction only will give a better optical surface as it's possible to bend more accurately than with my previous methods. The left and right edges will have curving to them just as a non-corrected lens, but I don't see that as a problem. The problem area with non-corected lenses are the top and bottom edges IMO.

-I will try to make the corrective surface on the oilprism instead of the waterprism. I was worried that the lexan wouldn't be able to withstand the turpentine as it is a strong solvent, but after bathing a piece of lexan in red spirit for ten hours I'm confident it will work (I didn't have any turpentine with me at work to test with).

-Pure turpentine still works great as a substitute for turpentine oil. They are basically the same thing, turpentine contains 75%-100% turpentine oil addording to the data-sheet.

-The water does seem to attack the epoxy-glue somewhat and silicone sealant works better for the water. However silicone sealant isn't overpaintable, which is a drawback. The paint will form drops on the surface of the silicone after a few seconds. My final version will probably have silicone instead of epoxy for the waterprism. I'm not sure how the silicone sealant stands up against turpentine.

-I want to try making a horisontal expansion lens as well. It shouldn't be any more difficult, all I have to do is design it backwards and rotated 90°

-I wish I had a projector which didn't have such an extreme short-throw lens. It does however make my design very versatile and if it works with my projector then all other projectors with longer throw should be able to use a similar lens.

-If it's possible I might try to make a 2.35:1/1.78:1 adjustable lens, but I'm worried about the amount of chromatic aberrations and barrel distortions becoming too bad. If I compensate the geometry in only the vertical direction the problem will be reduced, however.


I hope I will have the time to experiment more in the future, I might have to send my projector in for repair (again) and my left B&W CDM7-NT speaker has started to make a fretting noise from the bass-driver so I will have to send that in as well. I can't possibly watch movies without the speaker or projector. I will be dead for the period they are away.


Tor Arne

[woneill]

Hi Guys,

Interesting ideas!

I have previously been exploring the topic of anamorphic lenses myself, but in my case I was looking into using a pair of cylindrical lenses (one each PCV & PCX - both with the same focal length) to expand the beam horizontally, and possibly also using another pair to compress the beam vertically at the same time. (This would reduce any distortion in a single axis.)

Unfortunately, the lenses I have been able to get so far are very poor quality, and the results were unimpressive.

Your use of liquids to form the prism body is cool. Have you considered exploring those transparent epoxy packs available for use in embedding things within a plastic block? You might be able to get away with only needing one liquid device. (I'm thinking about leaks etc.)

Bill.

[tahustvedt]

Is it somekind of molding material? The material would have to have the right refraction index, somewhere close to turneptine. If the refraction index is different the angles need to be changed.

Interesting idea about compressing and expansion working together.


Check out this patent with lots of ideas but unfortunately no calculations:

http://appft1.uspto.gov/netacgi/nph-...DN/20020063975

It has many auggestions for how to make a lens and how to correct different artifacts.


Tor Arne

[tahustvedt]

I don't think this has been mentioned before.

The right way to mount the lens is as follows. If the projector is ceiling mounted the peak of the waterprism should point downwards and the peak of the oilprism should point upwards. Like I said it will work the other way too, I guess you have to try for yourself which way is best.


Tor Arne

[woneill]

Hi,

Of course I can't find a link when I want one, but to give you some ideas of the properties, and see if the stuff is in the ballpark, try these links:

http://www.loctite.com/pdf/doming.pdf
http://www.loctite.com/pdf/ComparPro...learEncaps.pdf

The stuff I was actually looking at is generally available from Home Depot in the US. It is clear, transparent, and designed for encapsulating things into table-tops, trays etc.

I was thinking of using it to make large PCX field lenses for the LCD panels instead of fresnels, but when used correctly, the fresnels weren't too bad.

You put whatever you wish to encapsulate on the surface, pour over the epoxy as if it were water, and let it set. (Of course, you must build a waterproof frame around the edges...)

I have seen this used with thicknesses up to an inch.

Bill.

[woneill]

I tried the Patent link - it will definitely take me some time to digest...

Bill.

[tahustvedt]

It would be possible to make a mould from glass. The problem would be getting the prism out of the mould, even if the mould was expendable.


My apporach to the lenses is a bit silly as I'm trying to make it small. By making it a bit larger it will work better but it will be ugly. I just mention it so you guys know why I'm making so many different versions.


Tor Arne

[hoxford]

For the loctite materials, the problem is that the current DIY lens design is based on the the optical properties of turpentine oil and water. It seems that the refraction and dispersion properties of both materials are important to get the desired bending of the light while reducing chromatic abberation. This is what I've read, anyway.

However, it seems that "commercial lenses" of this sort (liquid filled prisms) just some sort of mineral oil. I'm not sure how the correction for chromatic abberation is handled there.

There's a patent on handling chromatic abberation in prism based lens systems...

http://patft.uspto.gov/netacgi/nph-P...S=PN/4,704,008

...but it's over my head at the moment.

[tahustvedt]

It's way over my head too. I think I'll stick to what works for now.


Tor Arne

[hoxford]

I made my first attempt at working on the lens yesterday. It didn't go too well.

I had a very hard time getting clean, straight cuts in the glass. It didn't break well and when I did manage to get something of a straight snap, the edge would be very "wavy".

After finally getting a few pieces that were close to desirable I attempted to glue them up. That didn't go well at all. I just couldn't get it to come together in the right shape. I ended up with epoxy everywhere and a shape that would never work. The result went into the trash.

I know I am clumsy but this was just ridiculous.

I think I'll try something other than the all glass and epoxy method of construction. Since I don't have access to aluminum bending gear, I'm going to search for some kind of small 'L' bracket material to make a frame, then glue the glass into the frame.

[tahustvedt]

I made some formers from cardboard which I put between the surfaces of glass while glueing. I also use a lot of clear plastic tape and align the pieces flat on the table on the tape before I glue so that I can just swing the parts together using the tape as hinges.

It should be possible to make a wood frame for the prisms and painting it and then coat it with epoxy-glue thinned with red-spirit.

I started assembly on the failure-prism again today. I doscivered that the glue had released the aluminium frame where the frame wasn't painted, but where the edge of the frame was covered in paint the glue stuck wery well. So I painted the edges today and will glue it together tomorrow.


Tor Arne

[acolby]

Tor,

Great work so far!

I made a prototype completely out of lexan for the sides and surfaces of both prisms. This was about a week ago and no leaks yet. For someone who does not have acsess to metal and plate bending press i think the lexan is the way to go for the side pieces. However it does not work well for the light surfaces. Way to reflective. I am going to get some high quality non reflective glass for the finished version.

My observations so far:

My prototype works fairly well. I also have a short throw projector (panasonic 711xu) and the barrell distortion is significant. I haven't tried your outward curvature of one lens surface yet(not sure how to get the proper curvature drawn out and cut)
I also noticed different areas of the projected image were slightly out of focus. will have to see if this improves using better glass and tighter tolerances when mounting the two prisms.

Has anyone tried using mineral oil instead of turpentine?


Adam

[hoxford]

Originally posted by tahustvedt

I was worried that the lexan wouldn't be able to withstand the turpentine as it is a strong solvent, but after bathing a piece of lexan in red spirit for ten hours I'm confident it will work (I didn't have any turpentine with me at work to test with).

Be careful with the lexan and turpentine. I was thinking of doing that too (oil prism of lexan) and just did a few searches on lexan/polycarbonate/turpentine with somewhat mixed results. One datasheet said that polycarbonate was resistant to turpentine. Several others listed turpentine as possibly destructive. I think I'll stick with glass.

[PigPen]

Mineral oil is the key. It should not attack the lexan. I am using Edmond Scientific Glass which was quite expansive. It seems to have more reflection than I was expecting. I have the basic prisms bonded together and am now tweaking things in. Thanks to Tor for getting things going! Hopefully more AVS people will help contribute as well.

PP

[tahustvedt]

I found a page stating that care should be taken with using turpentine with lexan. I guess soaking the lexan isn't a good idea, then.

When I ask about mineral oil at the pharmacy they have many different kind of oils available. Does anyone know what the appropriate oil is called?

I'm glueing the prism right now and will fill it later this evening. I will make a new prism soon with compensation in only one direction.

I will make some scetches describing why the compensation can give problems.


Tor Arne

[tahustvedt]

I took some pictures of the prism while glueing. I forgot to take a picture of the top brace. Sorry!


Here the flat side has ben glued to the frame. The brace is next.


The brace has been glued to the frame and the correction-surface is setting.


The finished prism prior to filling and painting the outside of the frame. Notice the brace which shapes the peak-side of the corrective surface.


Tor Arne

[PigPen]

Get a light mineral oil. Whatever you do DON'T MIX THEM! They separate. Don't even mix different brands, pick one and stick with the same.

Learned this the hard way.

PP

[tahustvedt]

I'll try to explain to you the main reason why I want to try correcting just the top and the bottom of the picture.

In the first picture you see the prism from the side. The red lines describe how the lexan would be bent if it was corrective. This compensates for the barrel-distortion but it can introduce another problem. Since we won't be able to position the projection beam accurately on the surface of the prism the beam might be closer to the top or bottom of the prism. This would actually change the peak angle of the prism, if the projection beam exits closer to the peak the prism angle will be smaller than it should be and vice versa. The blue and yellow lines shows how the angles closer to each edge are different from ideal (black edges).


Looking at the prism from the side.

In the second picture we see the prism from the top. Correcting just the top and bottom of the picture by curving the lexan according to the red lines in Figure 2 will not be a problem since the lens doesn't change the horisontal width of the picture. It will be easy to center the lens well enough to get an even focus.


Looking at the prism from the top.

If one wants to correct in both directions it would be best to correct in one direction for each surface, and not like I have done with my prisms up untill now. For example bending the front surface by the vertical axis and bending the aft surface by the horisontal axis. I have been correcting the same surface in both directions all the time.

I don't think the focus drift will be as bad when correcting in only one direction, which might be another benefit from going with this design.


Tor Arne

[hoxford]

I'm still working to get a basic prototype built... no fancy curved, geometry correcting prisms for me yet.

I learned the value of oiling my glass cutting tool yesterday. That trick finally allowed me to make clean, straight cuts.

I also picked up some thin sheet metal and made 'end caps' for the oil prism. I measured out the 24 degree angle, added in a bit of room for a flap to bend down around the edges, and cut the metal out with snips. Then I bent the edge down with a vice and hammer to get a nice sharp 90 degree bend. What I ended up with are top and bottom wedge shaped 'cups' to glue the glass into. It made the assembly process much easier.

I'll work on the water prism today.

[hoxford]

I also wanted to share a thought I had on blackening the inside of the oil prism.

The concern is that turpentine will attack any kind of paint used. I was thinking of mixing lampblack (the pigment used to make dark paint) in with the epoxy, then spreading the epoxy over the surface to blacken. If the turpentine attacks the epoxy we're screwed anyway. The other trick would be to roughen the surface of the epoxy to make it more light absorbing.

I haven't tried this yet. That'll be phase two.

[rwhitley]

Arne,

Thanks for your project so far. Printed out your original post from AVS before it got yanked and built my first prototype on July 1st weekend. Amazed at the results.

Now I am working towards #2. I found assembling all of the pieces of the prism pretty hard and a little tedious, figured there must be an easier way. I found a 4" PVC fence post material at Home Depot and had them cut it in a 24 degree wedge and then just glued my acrylic face plates on both faces for my turpentine prism. I will take pictures and post them later. But this was way easier and I trust it not to leak much more. Found a place on the internet that sells even larger square plastic tubing and I am waiting for it to arrive for my water prism.

I am still using lexan for the sufaces until I am sure I have the design that I want. I found this place for non reflective glass www.framingsupply.com . 98% transmission almost no reflection and the pricing looks good. If my square tube idea works I should be able to order the glass faces precut.

I will try mineral oil for the next prototype and let everyone know what I find out (if no one else answers the question first).

Rick

Oh yeah and the if square tube thing works, I am sure it can be ordered in black.

[PigPen]

Tor,

I am having a bit of a focus problem with mine. When I look through it, it is crystal clear. I can arrange the prisms and get a little better focus, but not even close to razor sharp. Did you ever run into such problems and find the solution?

PP

[tahustvedt]

My flat prisms don't give any focus problems that I have noticed, but the corrective prism does give a slight focus change which cannot be corrected completely with the focus-lens of the projector. I thought maybe it was because I used two different materials for the surfaces so I have made a new prism now with lexan on both sides.

The square tubing is a good idea and should make construction much simpler.


Tor Arne

[tahustvedt]

I have moved the projector farther away from the screen and this enables me to reduce the zoom and fit the picture inside my previous smaller lenses. The prism with lexan on both sides didn't seem to induc any more focus-change. I guess it's just the correction that does it, then.

I haven't made any new lenses since my last post, I've been busy with other stuff. I did some thinking though. I think just bending one side (bottom, prism-peak side) of the surface is necessary to give a satisfactory correction. When the lens is angled to give uniform picture-geometry the barrel distortion is only visible at the sides and bottom of the picture. the top is straight. I don't know why, but I guess it's because the top edge is just projected almost straight out of the projector and not at such a dramatic angle like the other edges. Of course, this is when the projector is ceiling-mounted. Table-mounting means it goes the other way round.

If you look at posts made by owner of Panamorph-lenses on AVSforum they say that they have accepted that the lens compresses the bottom of the picture more than the top but I think they're just angling it improperly. They're probably angling it so that the barrel-distortion is equal around all the edges.

I will see what kind of square tubing we have at work that I can use for the new waterprism.

I'm not using the newest lens design now, I'm using the previous one that wasn't painted because the mounting came out better on that one, and now that the projector is not as zoomed out it's big enough too.


BTW.
If you're using flat prisms and don't get perfectly even focus top to bottom it's because of the lens'shift that the lenses give. It's just one of those things we'll have to accept I guess. At least for now. Angling the projector back up will fix the focus but the picture will be distorted.


Tor Arne

[chainsaw]

Hi Guys,

I only found this forum today, I was really the DIY lens project when it got going on AVS and was upset when it was removed. Glad to see the posts have continued.

I have finally got 2 weeks holidays and hope to get a chance at making one of these lenses. Just a couple fo things,

How do I go about determining how big to make the prisms. Do I use the measurements on the german website as a guide for my first prototype ?

I gather the glass is used for the oil prism, and the lexan used for the water prism ?

Tor, I noticed in your pictures one of your prisms is all glass on all sides and on other pictures you have a metal frame on some of your prisms?

Sorry if these questions sound stupid. There is so much scattered info, I am just trying to find a starting point.

FWIW, my projector is a VT540.

[tahustvedt]

No problem.

I make the turpentine-prisms all glass and paint the outside surfaces black after assembly and filling. They are glued together with two-component epoxy-glue. No leaks yet.

I make the waterprisms using aluminium frames to which I glue the two glass-surfaces or lexan surface. I have used epoxy-glue for most of my waterprisms too but most of them have sprung leaks and the prism I made with silicone sealant hasn't leaked so I'm switching to that now. The german website describe the same problem/solution.

I didn't use the dimensions from the german website, only the angles, instead I tried to make the prisms as small as possible. To find out how big the prisms need to be you can hold a piece of paper in front of the projector-lens and see how large an area the projection makes. The surfaces of my waterprism, which is the largest prism, are 100x110mm on the model I'm using now. You may want to make it a little larger than that to be sure the picture can actually fit inside the lens.

I only use lexan for the surface that I need to bend. I did make a prism with lexan on both sides but it turned out to be very flexible and the flat side of the prism didn't turn out completely flat. I recommend you either use glass on both sides or, if you're making a corrective prism, glass on one side and lexan on the other. The corrective prism isn't exactly perfect yet and it's very difficult to get right though. The last one I made turned out distorted.


Tor Arne

[rwhitley]

Chris,

If you are joining the rest of us, how about testing mineral oil instead of turpentive to see if it works?

Rick

[chainsaw]

Tor,

thanks for that. It is starting to become clearer now. Just a couple more things.

You mention that the water prism is the larger of the prisms, how do you determine the ratio of how big it should be compared to the oil prism ? If i hold the paper up in front of my projector, i will base that size on the water prism, is it possible to make the oil prism the same size ?

when you mention you paint the outside surfaces of the oil prism black, do you mean the whole prism ?

Thanks again.

[tahustvedt]

I only paint the underside and left/right sides. The optical surfaces can't be painted or the paint would block the light.

The ratio of how big it is doesn't seem to matter. You can make them as big or as small as you like, but to bring the lens as close as possible to the projector, I made the turpentineprism small. The smaller the turpentineprism is, the shorter the bottom surface will be, and the closer the waterprism will be to the projector.

As rwhitley say, you could try mineral oil instead of the turpentine. I won't guarantee that it works as well as the turpentile as I haven't tested it myself.

I'm not sure if the mineral oil will work with the angles we are using, the light may be refracted sifferently in the mineral oil. I dunno!


Tor Arne

[chainsaw]

so the larger water prism is the one that is placed infront of the projector lens ?

I just noticed that my vt540 has the air vents blowing out the hot air directly under the lens ! I wonder if this will be a problem !

[tahustvedt]

No, the smallest turpentine-prism should be closest to the projector-lens. The projection-beam wouldn't fit inside the prisms if the small prism is farthest from the projector.

I don't think the heat would be a problem as long as it doesn't blow directly at the prisms.


Tor Arne

[rwhitley]

Mineral Oil has the same (or very close) refractive index, so in terms of the compression of the picture it should work. The question is more on dispersion.

The water prism causes a blue blur, the turpentine a red one so they offset each other. The mineral oil may not do this as well, however the Panamorph uses minerial oil so it likely does as good or better a job.

I am currently having focus problems with prototype 1.5, but I believe my 24 degree angle prism may be more like 26.5 degrees (can't seem to find my protractor and I keep forgetting to buy a new one). If this is the case, would this potentially cause my focus problems?

Rick

[tahustvedt]

I don't now. I don't get any problems with focus with my non-corrective lens, but my corrective lenses have so far been impossible to focus completely. The less correction the better the focus has been though.

I still haven't made any new parts, I'm flying south to visit myparents today so I won't be able to do any work this weekend either.


Tor Arne

[woneill]

Tor,

I am crap at glueing things - especially where liquids are concerned, so I went and bought a cinema anamorphic projection lens cheap off Ebay.

I'm crap? Yeah, but I found out something interesting:

Your issue about focus shift between top and bottom is something the designers of this lens faced, and they solved it by having TWO sets of corrected prisms.

Yup, there are two identical prism combinations in my apparatus (each a prism doublet corrected for chromatic aberations) - the first set shifts upwards, and the second set, arranged upside-down, shifts downwards again.

The trick is to angle the two sets so that the shifting and compression is even in both directions (up and down) and thus the image is largely undistorted. Each prism only provides half of the anamorphic compression, resulting in a really nice image.

Hope this helps.

Keep up the good work,

Bill.

[tahustvedt]

Cool!

What lens was that? The Super Panatar?


Tor Arne

[woneill]

Hi Tor,

I don't exactly know the details. It was sold as a "Hilux" and adjusted for a 200ft throw, but other than that I don't know more than I can tell from simple observations.

It doesn't have any lenses as such - just the two sets of prisms. It is about a foot long and four inches in diameter (obviously not intended for a very wide-angle setup), and on first tests produces a very nice image on my wall despite the fact that it needs a real good cleaning. (I'm also going to put a tripod mount on it so that it is fully compatible with my OHP-style optics.)

I manually tweaked the angles on the prism sets until they were balanced and gave the appropriate compression, and sat down to enjoy The Matrix...

I was also thinking of your corrective problem, and am wondering whether it would be better to use a converging lens on input to your system, and a diverging lens on exit. (I might try this on mine if I spot any annoying effects once the rose-coloured spectacles come off.)

The idea is that if you can counteract the divergence of the beam on entry to the system, and then re-apply that divergence on exit, you would be working with parallel rays through the prisms.

You would need to match the converging/diverging lenses with each other and with the focal length of your projector, but it might be a good alternative to trying to glue bent tensioned pieces of glass...

Bill.

[Michael F T]

Is the lens like this??
Sounds the same.
Where did you get a double prism lens?

http://www.widescreenmuseum.com/widescreen/wingtr2.htm

[woneill]

no, more like this:

[woneill]

And this:

[Michael F T]

Does anyone know the specs for the solid versions of the prisms?

What are the Prismasonic dimensions and angles?

There is a company in the UK (and probably one in the US) that will make solid glass prisms based on specs provided.

But what specs?

Is there a formula that could be used?

[tahustvedt]

Here's a downloadable program for calculating optics:

http://www.astrion.de/download/download.html

I downloaded it but couldn't make much sense of it, but I haven't tried very hard either.


Tor Arne

[Michael F T]

What do you think of the concept of using a solid prism over a water/oil prism.

If I had a 2 special blocks of glass that could be cut with a standard knife and then cut them at some angle, is that a prism?

Is it just the glass that is bending the light?

If so, what about using a optically clear liquid plastic and form a prism?

Or have a prism manufacturer create the prisms?

Is it all about the angles involved or are the materials special?

Last question, have you ever tried putting the prisms on their sides and see if that makes an expansion lens?

[rwhitley]

The prisms on their sides do make an expansion lens.

You can use solid glass for the prisms, it is just extremely expensive to do so, and the angles would be different.

Rick

[woneill]

The reason that two prisms are normally used (oil/water) is the same reason that good quality optics use doublet lenses (glass/flint).

It is to correct for chromatic aberation.

The prism is the simplest way to demonstrate this - hold a classic glass prism up to white light and it will disperse it into its constituent colours. A lens is just a curved prism, and will also disperse light into its constituent colours. The shorter the focal length, the more the dispersion.

This is due to the refractive index actually being different for different wavelengths of light.

In optics, an achromatic converging lens is produced by matching a glass converging lens with a flint diverging lens. If the lenses are matched for chromatic distortion (the flint cancels out the chromatic distortion of the glass), the overall produced lens is still converging (glass has a more consistent overall refractive index than flint).

Thus, you get the classic achromatic doublet.

That is all that is going on with the two prisms (oil and water): their chromatic distortion properties cancel while allowing for an overall bending of the light.

You could do it with any two refractive media - as long as a balance can be achieved where the two prism materials cancel out the chromatic dispersion while giving an overall converging effect.

Thus if you could get the correct formulae and find appropriate materials from amongst the liquid plastics, transparent epoxies, glass etc. you would be able to make your prisms without TOO much trouble (people are able to grind their own reflectors for telescopes, which are FAR more difficult to do acurately than plane surfaces...)

Bill.

[Michael F T]

Thanks for the response, makes sense.

The transmission of the light would probably be lower too through a plastic. However, maybe not too much.

So the trick is getting the correct data to apply to a prism of different refractive indexes.

I still don't understand why 2 glass prisms would be all that expensive. I just can't figure out the sizes and angles for them.

I was hoping someone would have documented the details much like the Oil/Water version.

I'm still a little uncomfortable with liquid being so close to the projector.

[woneill]

Generally, prisms are made to very accurate tolerances for optical instruments. Anything specialised is very expensive.

If you wanted to make them yourself, or have blanks made to rough spec and finish them yourself, the price and quality would not be anywhere near the commercial ones, but that is not necessary for projectors.

Literally, with the correct materials, they would not be TOO difficult or expensive to make (or have made...)

Bill.

[ap0the0sis]

Could someone explain to me what a anamorphic lens is does and what its used for?

I read on a site that it is used to squeeze a 4:3 image to a 16:9 but wouldn't that distort the image? Doesn't make much sense to me right now....

I have a 4:3 projector, would i benefit from this?


ap0the0sis

[Glenn Refling]

ap0the0sis,

The anamorphic lens does indeed squeeze the image. The reason they're used by owners of 4:3 projectors is that they allow all of the pixels in your projector to be used in generating the image.

The trick to avoid distortion in your squeezed image is to pre-apply a distortion in the opposite direction. There are two means generally employed to do this. One way is to use an external scaler or PC to re-scale a 16:9 image to fill your whole 4:3 panel.

If you viewed this image without an anamorphic lens, it would show people tall and skinny and all things stretched vertically. Now placing an anamorphic lens in front of your projector causes the image to be squeezed back to 'normal' geometry. The big advantage is you are now using many more pixels to create the picture giving you a better resolution.

The second way of doing this is using a DVD player that allows aspect ratio settings. If you tell the player the aspect ratio is 16:9 and tell the projector it is 4:3 then the picture takes on that tall and skinny people look.

Hope that helps.

Regards,
Glenn

[ap0the0sis]

ahh, i see. make some sense to me now. i dont think this lens setup would work well for someone that is switching between tv viewing (4:3) and movie (16:9) right? This is more like one time setup and leave it for movies


got another question. how come these lenses are filled with fluid? Wouldnt it be better to use a solid piece of plexiglass and grind the prizm shapes from that? This way you can get the right curves to compensate for distortion?


justa thought

ap0the0sis