DIY anamorphic lens

[DArthur]

Craig, Jude,

I just check out the Image Perfect glass at "The Frame Depot" - It is not suitable for anything but pictures. The glass has a depth of field of about 3-4 inches. Anything beyond that gets very fuzzy. Looking through a sample at the store made me think of opening my eyes under water (with out goggles) - everything was blurry after about 4 inches.

I'll try plain glass first.

Darryl

[tahustvedt]

What kind of mineral oils did you use? What does the label say?

I asked for mineral oil at the pharmacy but they said there were so many different kinds for different applications and they couldn't help me.


Tor Arne

[JudeBarnes]

That type of glass is probably for UV protection (so that whatever you frame in it is protected from any sunlight, from deteriorating.)
It may be the same stuff I talked to them about. There may be another type, I forget the term now, which is clearer thatn normal glass. I watched Star Wars episode 2 last night and removed my keystone problem from earlier. I still do not have any barrel distortion but for some reason last night I noticed a very feint duplicate reflection of very bright spots of light on the screen itself. I think I need to make a new model with non-glass sides to defeat this.

[JudeBarnes]

The type of mineral oil I used had a label of the store itself. There were no other types to choose from that I could tell at the store I went to (a common pharmacy chain here in the USA)

It was "Walgreen" brand mineral oil. I will try to get some more specifics tonight from the label on the bottle. I wonder if possibly all the different mineral oils they had have the same "refractive index" ? (maybe try buying the cheapest, most common, first)

[tahustvedt]

So did you use water and mineral oil or mineral oil in both prisms? I'm starting to gain interest in this again.

I talked to Hitachi again today, I'm sending the projector back for repair (again)!


Tor Arne

[JudeBarnes]

I used water in one (larger) and mineral oil in the other (closer, smaller prism). As I understood it from talks with you Tor and other research, both have "chromatic abboration" unless you use them both together to cancel it out. I am curious though because the commercial model has both prisms filled with oil if I understand correctly.

By the way I did notice barrel distortion start to occur when I tried to squeeze the 16:9 image even further by tilting the front prism further. Even if the distortion is somewhat signficant I'm probably still interested in getting a full panel 2.35 film and just cropping the top off the image with masking.

Not sure if I'll make a second DIY screen that is 2.35 or just jimmy-rig my existing 16:9 screen so that I can quickly adjust it to 2.35 as needed.

[JudeBarnes]

By the way Tor now that you're interested in this project again I'm really curious if you (or all of us, together) can figure out some angles for optimal 2.35 -- I sent a pm to 'decinema' on avsforum to see if he knows. I'll post anything I can find.

IDEA: If the existing model prisms we are creating can be merely rotated futher to form a 2.35 squeeze -- with a similar amount of barrel distortion as the 'commercial model' -- seems to me you could make a new design that simply had the two prisms both independently rotatable... and marks on the side of the frame to designate where to turn them depending on which squeeze ratio you wanted. (thereby only needing the one lens to accomplish either).

Tor: On this subject, have you gotten an HTPC up and running yet or are you still using a standalone DVD player?

[tahustvedt]

I have no idea how to calculate the angles, I don't have the math-smarts to figure out the formulas for myself.

I wanted to try making a lens with hinged prisms, but I fear it may be a waste of time. If such a lens is to be made the prisms will need to be re-designed a little. I don't mean the angles, but you need to make sure that the edges have enough room for the picture as you rotate the prism. The peak tip of the waterprism will need to be higher or else when you tilt the prism down it will interfere with the picture.... I think.

I'm still using my standalone DVD-player, My projector had been away for three months so I kinda lost interest. But seeing the picture quality with my new ATi 9700 PRO I'm gonna build one when I have the money. The ATi kicks GeForce2 GTS bee-hind!


Tor Arne

[Nox]

After reading about this for some time, I finally decided to make a lens for myself.

I used mineral oil and the 24° angle.

It doesn't work well at all. Maybe I made it wrong. The image cannot be focused, the red and blue colors are seperating (even when simply looking through the lens) and it also creates a very bad barrel distortion (it bows extremely). To sum it up, the image is unwatchable.

I still don't know a lot about making these, so if anyone has explinations as of why these discrepancies occur, it would be most helpful if I were to make another.

[tahustvedt]

You have to make two prisms for it to work, did you do that?


Tor Arne