Just got my French Prisms - Page 7 - AVS Forum
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post #181 of 303 Old 10-29-2008, 06:06 AM - Thread Starter
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Thanks myky,

I wouldn't be jumping anytime soon, the wife would have my head as I have given to much time to this project. Your right about the prisms only being coated on the sides, I also believe the other prisms in question are also coated only on the sides.

Do you have a link to the article? I'll have to check out a bond movie and see how it does.
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post #182 of 303 Old 10-29-2008, 08:57 AM
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Hmmm it seems that I forgot to actually give the link in the previous mail. Here it is: http://www.zuggsoft.com/theater/prism.htm
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post #183 of 303 Old 10-29-2008, 12:12 PM - Thread Starter
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Thanks for the link.

Here are some pics of my finished enclosure. It's as finished as it needs to be since the shelf you see it sitting on in front of the projector will be enclosed and their will simply be a port hole (square) for the image to shine thru.






On the shelf





Like I stated earlier the inside was lined with velvet and it looks better in person since the flash brings out imperfections which aren't normally seen.
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post #184 of 303 Old 10-29-2008, 12:54 PM - Thread Starter
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Just checked that out myky,

I had seen that before, but never read the whole thing thru, nice to know. Still very affordable solutions for us DIY'ers.
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post #185 of 303 Old 11-12-2008, 10:10 PM
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I have still not got the prisms. Waiting is futile so I already started building my enclosure. I have made two prototypes. One is like oman321 has and one is smaller. I will add to the box the fine tuning trimmers so that I can easily modify the lens angle.

I am about to drill the holes but I do not know the size of the small prism.
Is it like this:

I confirmed that the bottom of the prism is 1.20 inch wide (30,5mm) and it is 2.755 inch (70mm) high.
But are the two longest sides about 3.464 inch long (88mm)?

The reason to confuse my mind is that in this thread there was pictures were the two longest sides were only 3.346 inch long (85mm).

So which to believe?

Anyway I will send photos about the project soon
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post #186 of 303 Old 11-13-2008, 07:37 AM - Thread Starter
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Hmm. not sure the website says 88mm
http://www.surplusshed.com/pages/item/l9113d.html
but the pics I have say 85mm.

I will try and check for you when I have a chance but likely not till tomorrow night.

Also I had called surplus shed a few weeks ago to see if they were still producing them and they said they were but they are waiting for them to come in. I guess they have a delay of some sort.

Please do post pics when you have time.
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post #187 of 303 Old 11-13-2008, 11:30 AM
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What are the angles of the prisms that are used for DIY lenses?
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post #188 of 303 Old 11-13-2008, 12:01 PM - Thread Starter
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Different prisms have different angles, I believe these have like a 20 degree angle.
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post #189 of 303 Old 11-13-2008, 12:06 PM
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The angle is 20. Hmmm... I forgot that. You can calculate it.
If the bottom is 30,5mm and the half of that is 15,25. Then the angles are 10, 90 and 80 (total has to be 180). So then we shall use following math:
X = tan80 * 15.25 = 86.48mm

Well it seems that it is between those two values what we have seen.
I need to calculate the bottom again to get the real value.
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post #190 of 303 Old 11-13-2008, 12:37 PM
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I calculated the wrong side. The hight is 86.48mm and if the bottom is 15.25 then the longest side is then 88mm

It is long time since I have use trigonometry but I managed to get it right.
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post #191 of 303 Old 12-05-2008, 12:04 AM
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Hi!
Finally I managed to snap few pictures of the enclosure. Still waiting the prisms, but everything else is ready. You can see also the mounting solution.
Give feedback
It is quite small and does not look so ugly as I thought.

http://s463.photobucket.com/albums/qq355/myky_1/
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post #192 of 303 Old 12-05-2008, 06:11 AM - Thread Starter
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Looks great myky,

I had sketched and contemplated going with an angled design like that, but when I decided to make it hinged and because it was such a small enclosure already I decided to just go with what I have.

Your case looks very professional, you really did a great job. I know you had mentioned making it so you could adjust the prisms and I suppose that's what the 2 butterfly nuts on top are for. Is this how you also plan to access the enclosure once you get the prisms? Must be killing ya not having the prisms yet, any ETA on them?
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post #193 of 303 Old 12-05-2008, 07:53 AM
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Yeah it is pain to wait But then again I had time to think and finalize the enlosure. The best estimate is 3 weeks. So it will go to early next year.

The butterfly nots are the "trimmers". I have 2 nots more for the bottom (not installed yet). I will glue those to prisms and that is it. The top of the enlosure is open so if I want to clean up the prisms, I just open the butterfly nots and open the hatch.

It took longer to design the mount solution
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post #194 of 303 Old 12-05-2008, 08:42 AM
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Hi myky,

the enclosure looks really nice Did you use MDF boards to realize this and painted the insides black?
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post #195 of 303 Old 12-06-2008, 01:08 AM
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The real hifi-people are going to laugh at me.......I used particle board!
The only thing I used that was because you can buy it smaller sizes.
You have to buy the whole board 220cm*140cm if you want the MDF(in Finland).

It was real pain to work with. All the edges were damaged and I had to use the putty (filler) to cover up those.

The inside of the enclosure is normal felt sticker what you usually put under the chairs. Eats the light and is soft enough to cover the prisms.
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post #196 of 303 Old 12-06-2008, 04:00 AM
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Quote:


You have to buy the whole board 220cm*140cm if you want the MDF(in Finland).

It's the same thing like here in germany. I also would have to buy a whole plate, although i don't need most of the material.
So i've asked several local cabinet makers if they could build such an enclosure for me. I'm still waiting for the response of one of them, who had 16mm black colored MDF boards.

The idea to use the felt stickers sounds good and it seems to work nice
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post #197 of 303 Old 12-11-2008, 07:38 AM
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Quote:
Originally Posted by myky View Post

Do not worry about the ghost image. All trophies that people are using for anamorphic lenses will have ghost image. So do not jump from one ghost image to another

Please read the great article about the DIY anamorphic lens (award plaques). Read specially the section "Reflections".

It just happens if you do not have good anti reflection coating. I believe that the French prisms are only coated from the sides, but how about the actual "lens" part? Anyway you will not get rid of the ghost image unless you will order your prisms from optic company or something (which will make the real AR coating and that means a special layer(s) to the surface of the lens where the light hits).

Personally I found the ghosting intolerable. I tried the HTB and CAVX lenses and their preformance was comparable to these prisms--but no ghosting! Frankly, the ghosting is so bad it is completely unacceptable. I don't think a few hundred bucks more is too much to pay for a markedly better image.
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post #198 of 303 Old 12-11-2008, 08:01 AM
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Hmmm... I have heard that in here (Finland) people have managed to get rid of the ghost image with fine tuning the prisms angles.
It might be that they do not see it or something. As you mentioned earlier that the projector plays one part in this (contrast ratio).
Anyway I will get into this when I get my prisms. If there is a way to get rid of the ghost image (or reduce it heavily), you will be first to know.

Do you still have the prisms?
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post #199 of 303 Old 12-11-2008, 08:07 AM
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Quote:
Originally Posted by myky View Post

Hmmm... I have heard that in here (Finland) people have managed to get rid of the ghost image with fine tuning the prisms angles.
It might be that they do not see it or something. As you mentioned earlier that the projector plays one part in this (contrast ratio).
Anyway I will get into this when I get my prisms. If there is a way to get rid of the ghost image (or reduce it heavily), you will be first to know.

Do you still have the prisms?

Yes, I still have the prisms.

I've tried fine tuning them ad infinitum. But good luck and hopefully you'll figure something out.

I think reflection also is effected by the internal angles of the prisms. If you look at the angle the prisms are placed at with regard to each other, on Mark's CAVX lens or the HTB lens, it is quite a bit larger than the angles at which the these lenses get placed at, so the internally generated reflection get reflected out of the back of the lens to the back or side wall instead of a portion being reflected back to the screen as a ghost image.
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post #200 of 303 Old 12-12-2008, 03:44 AM
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Just wondering that if you want to get rid of the prisms I would be interested of buying them I have been waiting the new prisms since 17.10.2008.

If they are OK and no scrathes on them give me a prize to work with
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post #201 of 303 Old 12-12-2008, 06:07 AM
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Quote:
Originally Posted by Person99 View Post


I think reflection also is effected by the internal angles of the prisms. If you look at the angle the prisms are placed at with regard to each other, on Mark's CAVX lens or the HTB lens, it is quite a bit larger than the angles at which the these lenses get placed at, so the internally generated reflection get reflected out of the back of the lens to the back or side wall instead of a portion being reflected back to the screen as a ghost image.

The CAVX MKII used 15 degree prisms where these "french" prisms are 20 degrees. You should therefore find that the displacement (angles required to produce anamorphic stretch) should be less, not more.

Even though these prisms are coated, you will still get some reflections on the side walls due to the fact that the prisms faces are flat. Ghosting on screen is an aligment issue, but also may be due to the TR where the further back you can mount the projector, the better.

Mark

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post #202 of 303 Old 12-12-2008, 07:10 AM
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Quote:
Originally Posted by CAVX View Post

The CAVX MKII used 15 degree prisms where these "french" prisms are 20 degrees. You should therefore find that the displacement (angles required to produce anamorphic stretch) should be less, not more.

Yes, that is what I said, sorry if I didn't communicate correctly.

Quote:
Originally Posted by CAVX View Post

Even though these prisms are coated, you will still get some reflections on the side walls due to the fact that the prisms faces are flat. Ghosting on screen is an aligment issue, but also may be due to the TR where the further back you can mount the projector, the better.

Mark

Yes, they all do that. My point was, yours do not put a ghosted image on the screen. HTB lens does not put a ghosted image on the screen.

I have tried every alignment you can imagine with the "French" prisms. At TRs up to 1.7 (my current PJ does not go higher than that), there is a ghosted image on the same side of the screen as the screen side prisms "fat" end. On the stretched picture, if credits are rolling up the center, then the ghosted image be at the edge of the screen. You will see about 60% of the credits (the other 40% are "off the screen").

If I feel like it, I'll try them with a friends projector at a 2.0 throw and see if the ghosting goes away.

The French prisms are two different sizes unlike yours or the HTB--one must be the "back" and one must be the "front". Further, the "front" prisms "short" side (i.e. fat edge) is not like yours and the HTB. The "front" prism of the "French" prisms is NOT an isosceles triangle like yours or the HTB. The front side of the front prisms is longer than the back. This means the "base" of the prisms is at a vastly different angle relative to the light path and screen that yours. I think the ghosted image is being reflected off that edge and to the screen as the angles look correct for that. I've tried every opaque thing I could to coat the edges and nothing stopped that reflection. I have to wonder if that front prisms was an isosceles triangle, would there be no reflection?
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post #203 of 303 Old 12-12-2008, 07:15 AM
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Quote:
Originally Posted by myky View Post

Just wondering that if you want to get rid of the prisms I would be interested of buying them I have been waiting the new prisms since 17.10.2008.

If they are OK and no scrathes on them give me a prize to work with

Hyvää huomenta, too bad I'm not going to Finland every 2 months like I used to, I might have been able to drop them off.

Let me see if I can try them at a 2.0 throw at a friends to see if he wants them (assuming they don't ghost at that throw). If he doesn't want them then I have not use for them and my wife is hounding me to get rid of much of the stuff I don't use!
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post #204 of 303 Old 12-15-2008, 12:47 AM
 
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wow wow wow. very good
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post #205 of 303 Old 12-31-2008, 01:23 PM
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Person99 how did it go with the prisms?
I have still have not got the prisms, but one thing is sure and that is they will not arrive for me this year
Happy new year and prisms!
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post #206 of 303 Old 03-27-2009, 10:52 AM
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Just got the prisms and they are working like trains toilet (cruel but works).

First findings:
-Picture quality ok (good sharpness)
-a little ghost image, but only can be seen in beginning of james bond Nothing with other material.
-can be used in very, very short projector distance. projector is 3m from the screen and with these prisms you can get 282cm wide and 120cm high image without any problems.
-a little smutty from the edges if you look computer test screen, but in movie you cannot see it.

What can I say. Best project I have ever done. Money to the bank I say!!!
I have seen Prismasonic's best product in action and I can say that this one does not loose too much. Of cource there is difference, but this is good product.

I will post few images soon.
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post #207 of 303 Old 03-27-2009, 11:19 AM
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Quote:
Originally Posted by myky View Post

I have seen Prismasonic's best product in action and I can say that this one does not loose too much.

All I can say is I disagree COMPLETELY with this. Either you really have low standards or you have only done a very cursory look at these. The ghosting on these is REALLY bad. The better the CR of your PJ, the more visible this ghosting is.

Prismasonics best does not have the ghosting, the color fringing, or any of the problems of these. Honestly, it is well worth the money to step up at least to the CAVX or HTB lens (I've compared all of them). You get even more bang stepping up from that.
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post #208 of 303 Old 03-27-2009, 01:16 PM
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I watch the movie and not the defects No really, I know what you are saying and this product is not for all projectors. I am nearly saying from my point of view (Panasonic AX200, less than 6000:1 contrast ratio).

And I have quite high standards when it comes to the picture (e.g. see my posts about the rainbow effect in the backlight lit LCD TV).
I have really tried to get the ghost image to pop-up to my eyes, but james bond is the only one. At least with my projector. It is so faint the I can babrely see it. It was quite an effor to take a photo off it.

For those who own better projectors WILL not like the image. I am writing an article about the whole project to dedicated magazine, so trust me I know what I am talking about.

And yes the prismasonic has 0 problems and so on (seen it in action more than one second).

I was about to order the bigger awards prisms, but then I managed to see few photos of the real size and they were really too big. I mean you have to be quite an artist to create a nice box out of those.
I knew that with small and quite good looking box I will get also ghosting.

I will post one ghost image and you will see how faint it is with ax200.
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post #209 of 303 Old 03-27-2009, 03:16 PM
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More details about the whole project:

The ghost image is there and you can see it in every scene where there is bright white object on black background. This means every start/end credits or very rare night scenes (watched the sin city without problems).
With higher contrast projectors it is an issue!!!

But here is for those who has ability to move your projectors:

I measured the size of the picture when the ghost image will sift to right so much that it can be removed totally with masking.
Details are: from 3m distance you need to project 62cm high and 146 wide image and they go over the screen. Of cource you need to finetune the prisms and stuff, but it works. You can now calculated your own distance from the screen and do the math.

The ghost image will become clearer with playing your projector zoom.
Look e.g. MIRAMAX logo. I can see the ghost image on right hand side (all depends which side your front prism is open, left or right). How close it is with the real logo, depends your zoom level and angle of the prisms.
So let me make clear. It is totally ghost free in the projected image with one precise setup. All others need to "suffer" it. For my projector it is not a problem. I will anyhow ignore at least the end credits, unless there is some joke coming up or some movie misstakes.

I could see the ghost image from ax200 with dynamic mode and only in the start/end credits or bond. With lamp mode cinema I had to really watch it.

So I really, really recommend these prisms to all the DIY people IF you have projector what is "bad" enough

When you really watch the movie you cannot see it. My earlier projector (panasonic ae300) had 2 dead pixels and I could see those from 4.5m away and the screen was only 200m wide and 114cm high. The knowing of the problem makes it worse. You will start to look that from every frame you can see. Same thing in the LCD TVs where you can see the rainbow problem.

This sounds like "Yes we can!" speech, but really the point is clear. Ghost is there permanently(except one setup), but you can live with it if you have low end projector and finetune the system enough.

Sorry about the long reply!

Sincerely
Myky
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post #210 of 303 Old 03-27-2009, 06:27 PM - Thread Starter
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myky, glad to hear you finally got your prisms. I was feeling bad for you. Yes there is some ghosting. My ghosting was greatly improved when I lined the inside of the lens case with velvet. I can barely see it like you said when there is a black background and white lettering. Terminator the Sarah Connors Chronicles has a "BARTLEBY" logo at the end where I see it to the right of the logo. I don't see it with subtitles, which is where it would really bother me. $125.00 vs. $600.00 is simply to great a difference for a very marginal improvement from all the reviews I have read.

I really don't have color fringing issues, I can see color fringe or CA at the very edge of the left side of the image which is simply taken care of with just slightly shooting the edge image on to the velvet border.

Overall my image is very pleasing and if I remove the lens the image without the lens is very comparable.

While I know screen shots can't do a projected image justice, this is one of my favorite screen pics which I have taken with the lens because of the fact that it shows a real world movie image with a grid. No ghosting, color fringe, simply a great picture and all who have seen in person agree.
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