AVS Forum banner
Status
Not open for further replies.
1 - 20 of 135 Posts

·
Registered
Joined
·
122 Posts
Discussion Starter · #1 ·
Compression varies over the height of the image. It's extremely annoying when there are vertical pans or if there are circular objects on the bottom of the screen (like car wheels).


http://www.csua.berkeley.edu/~ricky/temp/grid.jpg

http://www.csua.berkeley.edu/~ricky/temp/pattern.jpg


(These images will disappear in about a week from now - Today is August 23, 2001)


Is this due to the fact that my DL450 has too much of a vertical shift?


My screen width is 75" and the distance between the screen and the front of the projector lens is 113", not including the Panamorph.


It is floor-mount setup. If it were ceiling mounted, there would be more compression on the top of the image and less compression on the bottom of the image.


Other than the compression variations, everything else is amazingly good.


Any help would be greatly appreciated. Even someone telling me that there's nothing I can do about it other than buying a new projector with longer throw would be appreciated.
 

·
Registered
Joined
·
1,585 Posts
Its really strange that it is not a uniform distortion. Is your lens face parallel with the panamorph, i.e. is the projector tilted while the panamorph is vertical or vice versa?


------------------

David R. Smith


System info: NEC 9PG in progress, Dalite 60X80 Matte (I know), ATI Radeon 64mb VIVO, ATI 7.1 player w/DC's O IRE patch , WinME.
 

·
Registered
Joined
·
3,667 Posts
I've found that there is an optimal height of entry to the Panamorph. One has two major degrees of freedom, height and tilt.


Getting the optimal height and tilt isn't obvious. I eyeball the height and adjust the tilt by looking at the scattered light going through the Panamorph. I have a 4:3 screen so I can arbitrarily adjust the tilt. I suspect this has a major impact on how much vertical distortion one sees.


------------------

Ken Elliott
 

·
Registered
Joined
·
122 Posts
Discussion Starter · #5 ·
Projector is tilted slightly downward and Panamorph is tilted up slightly. This was all necessary to form correct 1.778 aspect ratio while keeping the projected image at the spot I want. Regardless of other movements, this distortion is unavoidable to me if I want to get the correct 16:9 aspect ratio.


As for light entry into Panamorph, I'm keeping the output light as centered as possible on the Panamorph output. One can see the outline of the light path on the Panamorph glass and I just make sure it's using the middle portion of the prism glass. I tried moving it around, but it did not change anything, which in itself is a good thing for Panamorph.


I've been trying to figure out how this works and I'm pretty sure that if my projector didn't have so much up-shift, it wouldn't cause this kind of distortion. I'm not too put off by it. I think I can get used to it for the most part. Movies with 2.35:1 or 2.40:1 ratio are not affected by this much at all because they have black bars at the top and bottom.
 

·
Premium Member
Joined
·
25,261 Posts
Doesn't the Davis have about the same tilt as most other projectors? Isn't the lens about the same height as the top or bottom of the image?


------------------

Noah
 

·
Premium Member
Joined
·
807 Posts
Shawn,


I see that positioning make a difference but can positioning also eliminate this vertical non-linearity? I will have once my new screen arrives the ability to adjust the total position of the screen on the fly.


Larry




------------------

DFAST is EVIL! BOYCOTT ANTI-CONSUMER 5C/DVI/HDCP/DMCA MANUFACTURERS!

Join Electronic Freedom Foundation
http://www.eff.org/
 

·
Registered
Joined
·
4,836 Posts
I personally find that non linearity to be unacceptable, especially for a product that is going to cost 2 grand.

I would like to see similiar images as projected through a Isco II lens.


Frank
 

·
Registered
Joined
·
6,227 Posts
Is this non linear compression being admitted or stated as an 'acceptable' compromise ???


When I initially saw it I assumed this was just a function of the projector / lens positioning and I noted the comment while keeping the projected image at the spot I want with this in mind I was assuming that a projector remount would allow for the exact 16:9 and no distortion...


Any other DL450 owners achieved a perfect Pannie install yet ??


Anyone else seen this distortion ???


------------------

[email protected]
HTPC without using windows... GUI Front Ends for Home Theater
 

·
Registered
Joined
·
1,286 Posts
That distortion looks pretty bad to me, but maybe it's not so noticable with video material?


In any case, FerretLover, what is the vertical position of your lens relative to the bottom of the screen? Is it at the spot specified with the Panny Lens calculator? If not, perhaps that is the problem. Can you reposition the image, keeping the 16x9 aspect ratio, but moving it off the screen, such that the distortion goes away? If so, those of us who are free to move our screens (unfortunately, I'm not one of them), would be able to get 16x9 with no distortion.


- Dave
 

·
Registered
Joined
·
122 Posts
Discussion Starter · #11 ·
Okay, so the distortion is unacceptably bad.


I've fiddled around with this stuff for hours now. I think I've got the hang of it. Given a DL-450, there's nothing I can do to avoid the unacceptable level of distortion if I want 16:9 aspect ratio. On the other hand, I found that the distortion starts getting unacceptable at around where the bottom plate of the Panamorph is parallel to the ground (or ceiling). At this point, I get just about 1.66 ratio. I've settled on 1.66 ratio. With dScaler, I just set my screen aspect to 1.66 and everything is cool. With WinDVD, I used YXY to create a profile that works for 1.66 ratio. dScaler just kicks too much arse!


At 1.66 aspect ratio, distortion is very much down to acceptable level (and I'm a picky man). Besides, I watch a lot of 4:3 stuff, so this is a good compromise for me.


I'd love to hear from people with other projectors and Panamorph. Then again, I'd love to hear from other people with DL-450 as well.
 

·
Premium Member
Joined
·
807 Posts
I am not saying it's necessarily unacceptable however I would love to see the same images thru and isco II as well!


Larry


------------------

DFAST is EVIL! BOYCOTT ANTI-CONSUMER 5C/DVI/HDCP/DMCA MANUFACTURERS!

Join Electronic Freedom Foundation
http://www.eff.org/
 

·
Registered
Joined
·
6,227 Posts
Ferretlover, Just to try and get some clarification (I am a DL450 user too) are you really saying that you are unable to get a distortion free image at 1.78 compression at any image placement (in other words perhaps missing your screen)??? I was hoping that this distortion was purely to accommodate a Pannie and get your screen position right...


------------------

[email protected]
HTPC without using windows... GUI Front Ends for Home Theater
 

·
Registered
Joined
·
122 Posts
Discussion Starter · #15 ·
PhatPhreddy, as far as I can tell, there's nothing I can do to get rid of the distortion. I have a 4:3 screen. Heck, it's just a WalMart(TM) bedsheet painted with flat white paint. I just used some black bedsheet (again from WalMart(TM)) to cover the top and bottom portion of the screen for wide-screen effect.


One could probably reduce the distortion slightly (very slightly) by moving the projector higher up off the ground whlie tilting it downward. Basically, by trying to artificially reduce the vertical shift, I think one can reduce the distortion slightly. Even so, I just don't see how this distortion can be avoided. I have a feeling that a projector with less vertical shift will do much better with Panamorph.


I could be wrong, but I just don't see how. I am happy with 1.66 ratio, though.


By the way, if you look at the images from Cygnus openhouse, you'll notice that the bottom plate of the Panamorph is more-or-less flat with the ground. I don't know what projector they were using, but that one must have less vertical shift than DL450. Either that or the image they were projecting wasn't really at 1.778 compression. On that image (Flight Sim), if you look carefully, you'll see that there is non-linearity. It's just slight, but I'm sure you'll be able to notice it.


Since their link was broken the last time I checked, here it is: http://www.cgns.com/721openhouse.htm
 

·
Registered
Joined
·
1,286 Posts
Ferret:


So the DL450's lens isn't even with the bottom of the projected image (with a floor mount)? I thought all projectors lined up with the bottom of the image. If not, I can see how it would be tricky to get it to work, but your idea of moving the lens off the ground seems like it might have merit. Perhaps Shawn can jump in and enlighten us?


(And, Dave - greetings to Caldwell. I grew up in Montclair.)


- Dave
 

·
Registered
Joined
·
6,227 Posts
I am beginning to think this may be a problem... The image shift is very common among 4:3 projectors and is especially common among the business machines, which must make up most of Cygnus's intended market. After all, most HT oriented PJ's will be 16:9 now or very soon and the design goal of the Pannie was (I believed) to assist in utilizing a 4:3 business machine and converting it to HT use...


I am amazed (if this is truly the case) that this has not come up during testing and design phase or been mentioned in any of the reviews so far.


To my eyes the above images are extremely distorted and if this is the best that can be achieved with a DL450 I am (getting worse by the minute) worried. Also (Shawn please forgive me here) the comment above "those are nice examples. You are absolutely correct, the process does introduce a vertical non-linearity to the image which increases with shift" does not sound as if this is something that is fixable.


Does no one else with a Pannie also have a DL450 or clone ??

Shawn, anything further to say on the subject ?? Have you been able to test with off axis projecting PJ's ??


At this stage I still fail to believe that this is the final outcome for so many projectors currently in use...


------------------

[email protected]
HTPC without using windows... GUI Front Ends for Home Theater
 

·
Registered
Joined
·
301 Posts
Quote:
Originally posted by Dave T:



(And, Dave - greetings to Caldwell. I grew up in Montclair.)


- Dave
Well, Dave, so did I! Nice place. I moved here in '90.

-Dave


[This message has been edited by dcarl (edited 08-25-2001).]
 

·
Premium Member
Joined
·
16,976 Posts
I brought home a Davis 450 so I could try it with my Panamorph.

My thinking was if I tilt the projector in a downward position the image exiting the lens would appear to be shooting straight ahead and the problem would be corrected.


So much for my idea. This did not work. I also tried rotating the Panamorph so the top was the bottom and the bottom was the top. All this did was to reverse the distortion. Problem still there.


This is not an issue with the Isco 2 because it is just stretching what is there. I tried it, works fine.

The downside is you need to zoom the projector to its smallest size to fit the picture inside the Isco.


The problem with the Davis ( not the Panamorph) is the lens has a deep curve. Part of the image is further away from the Panamorph then another part.

I think this could be what is causing the problem.



------------------

Alan Gouger

Thanks for supporting AV Science.
www.avscience.com
 

·
Registered
Joined
·
6,227 Posts
Stop the presses !!! This is pretty drastic news for me... So basically it is a non starter for Pannie + DL450 if you don't feel you can live with this distortion ?? I am curious how many other pre orders are DL450 users ???


Also I had the impression that many of the business PJ's shot an off axis image... Does this mean that this will apply to all of them ???


I am reeling from this news... After waiting this time and buying a second Pannie spot this week this is kind of a biggie...


------------------

[email protected]
HTPC without using windows... GUI Front Ends for Home Theater
 
1 - 20 of 135 Posts
Status
Not open for further replies.
Top