Does pincushion cause softness ? - AVS Forum
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post #1 of 26 Old 11-23-2010, 12:38 PM - Thread Starter
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I seem to have quit a lot of pincushion with my projector using my prismasonic lens.

For me the image looks like its lacking in sharpness, or it could just me being picky!!

Just wondering if pincushion would = lack in sharpness in some way ?
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post #2 of 26 Old 11-23-2010, 03:08 PM
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Pincushion generally results in geometric distortions. You can correct this using a curved screen.

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post #3 of 26 Old 11-23-2010, 03:43 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

Pincushion generally results in geometric distortions. You can correct this using a curved screen.

Its to late I dont have a curved screen installed. Will tilting the lens down more help ?

All so would it reslult is a less sharper image ?
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post #4 of 26 Old 11-23-2010, 04:15 PM
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Did you try my suggestion from your other thread re softness? It sounds like you've got a less than ideal setup so you're suffering from both pincushion due to a short throw and softness due to a prism lens. While there are lots of adjustments you need to make when setting up a lens, it could be that you might have to accept some limitations in your particular setup.

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post #5 of 26 Old 11-23-2010, 04:18 PM
 
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Quote:
Originally Posted by jamieuk147 View Post

Its to late I dont have a curved screen installed. Will tilting the lens down more help ?

All so would it reslult is a less sharper image ?

If ceiling mounted, the lens will need to be tilted down slightly. What you want to achieve is an EVEN amount of pin cushion top and bottom. Use a white field or a bright image so you can see on screen clearly.

Then to check alignment, you should lens shift up and down and you will see the curved come down off the frame. It should start to appear right in the middle of the screen at the top. The JVC has a good green grid to check this. What PJ are you using?

You should also check rectangular alignment on screen before the lens goes into place. This will ensure everything is aligned so once lens is added, the alignment will be easier.
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post #6 of 26 Old 11-23-2010, 05:32 PM
 
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Pincushion has nothing to do with soft focus. Unless you have a Panamorph with a corrector piece it will always be soft at the edges. If you do have the corrector, you may not have the appropriate one. Correctors are pre-set for certain throw ranges. Panamorph make several different ones. If you have the wrong one your image will be softer than expected.

The beam of the projector should pass through the center of your anamorphic lens. You have to tilt, vertically and horizontally offset, and yaw the lens to achieve this. If your projector image is offset to one side then you may have to rotate the Panamorph lens as well, as you will have some slight geometric distortion on the side furthest away from the projector that can only be adjusted by rotation (and then not perfectly).

If you are using offset with your projector, even though the projector casing is level and at right angles to the screen (or should be), the beam will be angled. This - the beam - is what you have to align your lens to, not the projector casing.

If your soft focus is to one side, you might not have the lens centered horizontally on the beam. Even a couple of millimetres out can be critical with prisms. If the softness is at either top or bottom, the tilt of your lens may not match the beam's angle of tilt. It's an iterative process, getting lens alignment right.

Another thing with prisms is that they slightly displace the image to one side or the other, by up to a couple of inches. You can center your 16x9 image and then find that your scope image is offset to the right or left. There's no cure for this, unfortunately. It's a "prism thing". You just have to decide on the best compromise position.

What Richard said about evening up pincushion is right. If the tilt of your lens is not correct then either the top or bottom edge will have more or less than the opposite edge. The sum of the pincushion a lens will induce is shared between top and bottom edges. If your tilt is wrong it can be all to one edge, top or bottom. The aim is to even it up by tilting the lens appropriately, so that the pincushion sum is shared (and thus at least subjectively minimized).

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post #7 of 26 Old 11-24-2010, 12:34 AM
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Quote:
Originally Posted by jamieuk147 View Post
Its to late I dont have a curved screen installed. Will tilting the lens down more help ?

All so would it reslult is a less sharper image ?
Tilting helps to even the pincushion out top to bottom, but it won't correct the pincushion. What projector are you using and what is the TR your using with your PRISMASONIC lens? What model is this? Does it have the FE (front element)?

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post #8 of 26 Old 11-24-2010, 01:09 AM
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I believe it is a Prismasonic FE1500R combined with an Epson 8500UB, hopefully Jamie will confirm this.

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post #9 of 26 Old 11-24-2010, 03:56 AM - Thread Starter
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Quote:
Originally Posted by Kelvin1965S View Post
I believe it is a Prismasonic FE1500R combined with an Epson 8500UB, hopefully Jamie will confirm this.
Yes Kelvin you are right!

I have the HD dune base player doing the V stretch

This might not make sence but when I see closeup images on my ptojector, like a face, it looks super sharp! but the mid to long range shots dont look that sharp to me.

My 8500UB doesnt support v stretch mode so I am using a zoom option on my HD dune base player which seems to stretch the screen verticaly, but not sure if this is the normal v stretch Method that most projectors use
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post #10 of 26 Old 11-24-2010, 04:53 AM
 
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Quote:
Originally Posted by jamieuk147 View Post
Yes Kelvin you are right!

I have the HD dune base player doing the V stretch

This might not make sence but when I see closeup images on my ptojector, like a face, it looks super sharp! but the mid to long range shots dont look that sharp to me.

My 8500UB doesnt support v stretch mode so I am using a zoom option on my HD dune base player which seems to stretch the screen verticaly, but not sure if this is the normal v stretch Method that most projectors use
When you say 'mid to long range' shots... Do you mean things in the background?? They will be out of focus in any setup as the camera will be focusing on the main characters etc.. Or do you mean something else? Because LCD projectors are not renowned for being DLP sharp.. Could be a projector setting you might to play with...

To know if you have vertical stretch working. Put on a scope film (not the main menu) where you have black bars top and bottom. (Some dvd players and PJ's also call vertical stretch zoom). When you apply this you should see the black bars disappear and the image will now fill the entire height of your screen. Everyone on screen will look tall and thin.. That's vertical stretch..

Your lens will then stretch the light beam by 33% in the horizontal plane to restore the geometry. The result will be cinemascope but with no black bars.
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post #11 of 26 Old 11-24-2010, 05:07 AM
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Quote:
Originally Posted by jamieuk147 View Post
Yes Kelvin you are right!

I have the HD dune base player doing the V stretch

This might not make sence but when I see closeup images on my ptojector, like a face, it looks super sharp! but the mid to long range shots dont look that sharp to me.

My 8500UB doesnt support v stretch mode so I am using a zoom option on my HD dune base player which seems to stretch the screen verticaly, but not sure if this is the normal v stretch Method that most projectors use
You should use a grid test pattern to judge sharpness. You can generate your own, or there are several available online. Here's one from AVS:

http://www.avsforum.com/avs-vb/showthread.php?t=948496
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post #12 of 26 Old 11-24-2010, 01:15 PM
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Quote:
Originally Posted by ilsiu View Post

You should use a grid test pattern to judge sharpness. You can generate your own, or there are several available online. Here's one from AVS:

http://www.avsforum.com/avs-vb/showthread.php?t=948496

he did start another couple of threads earlier this month on this exact topic:

http://www.avsforum.com/avs-vb/showt...125&highlight=

http://www.avsforum.com/avs-vb/showt...055&highlight=

And the issue of softness has come up a couple of times already, so those trying to help have a background of the issue:

http://www.avsforum.com/avs-vb/showt...734&highlight=

http://www.avsforum.com/avs-vb/showt...268&highlight=

OP, what proejctor technology have you owned before? It maybe going from a DLP (as example) to LCD, the differences in sharpness are becoming more apparent as you spend more time with your new projector.

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post #13 of 26 Old 11-24-2010, 01:43 PM
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Quote:
Originally Posted by rboster View Post

he did start another couple of threads earlier this month on this exact topic:

http://www.avsforum.com/avs-vb/showt...125&highlight=

http://www.avsforum.com/avs-vb/showt...055&highlight=

And the issue of softness has come up a couple of times already, so those trying to help have a background of the issue:

http://www.avsforum.com/avs-vb/showt...734&highlight=

http://www.avsforum.com/avs-vb/showt...268&highlight=

OP, what proejctor technology have you owned before? It maybe going from a DLP (as example) to LCD, the differences in sharpness are becoming more apparent as you spend more time with your new projector.

Why so he did! Maybe you could create a sub-forum called "questions from jamieuk147" so it'll be easier for him to track the answers (and remember if the question had already been asked)
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post #14 of 26 Old 11-24-2010, 01:57 PM - Thread Starter
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Quote:
Originally Posted by ilsiu View Post

Why so he did! Maybe you could create a sub-forum called "questions from jamieuk147" so it'll be easier for him to track the answers (and remember if the question had already been asked)

hahahaha!!!!!!
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post #15 of 26 Old 11-24-2010, 09:02 PM
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It would be interesting to hear from the OP as to whether or not he gets a much better picture by NOT using the lens and just doing simple zooming!
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post #16 of 26 Old 11-25-2010, 01:10 AM
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I did ask that question on (another) one of the OP's threads, but I guess he was too busy creating the next thread.

I did have to wash afterwards though as I felt dirty mentioning the zoom thing.

Zooming: Been there, done that, bought the lens...
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post #17 of 26 Old 12-06-2010, 04:31 PM
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You should use a grid test pattern to judge sharpness. You can generate your own, or there are several available online.


Yes, a grid pattern will allow you to adjust your focus such that both the vertical and horizonal lines share an equal amount of "fuzzieness". This would represent the best focus you could get...all other things being dialed in. Two prism setups also introduce an amount of chromatic aberration or CA. In many cases the CA is the greater offender in terms of apparent focus.

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post #18 of 26 Old 12-06-2010, 07:13 PM
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Quote:
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You should use a grid test pattern to judge sharpness. You can generate your own, or there are several available online.


Yes, a grid pattern will allow you to adjust your focus such that both the vertical and horizonal lines share an equal amount of "fuzzieness". This would represent the best focus you could get...all other things being dialed in. Two prism setups also introduce an amount of chromatic aberration or CA. In many cases the CA is the greater offender in terms of apparent focus.

Based on this there is absolutely no question in my mind that I would settle for a prism based anamorphic lens. I will stay with zooming until I get drunk enough to squander $10,000 on an Isco 111 !
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post #19 of 26 Old 12-06-2010, 07:33 PM
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Quote:
Originally Posted by taffman View Post

Based on this there is absolutely no question in my mind that I would settle for a prism based anamorphic lens. I will stay with zooming until I get drunk enough to squander $10,000 on an Isco 111 !

When you're ready to pay that price for an Isco, let me know - I'll sell you mine, then buy a brand new one with a CineSlide and still have a several grand left.

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post #20 of 26 Old 12-06-2010, 08:15 PM
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Clearly, he has no idea

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post #21 of 26 Old 12-07-2010, 12:08 PM
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Quote:
Originally Posted by taffman View Post

Based on this there is absolutely no question in my mind that I would settle for a prism based anamorphic lens. I will stay with zooming until I get drunk enough to squander $10,000 on an Isco 111 !

Squander would be right at that price. I'm second in line behind HogPilot for that . We can fix you up and have an open bar AVS party afterwards. Cheers!
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post #22 of 26 Old 12-07-2010, 06:32 PM
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So what is the going rate for an Isco 3 in the US?
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post #23 of 26 Old 12-07-2010, 06:44 PM
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No "real" price talk allowed. I was pushing it already (Sorry bout that admins).
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post #24 of 26 Old 12-07-2010, 09:30 PM
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So what is the going rate for an Isco 3 in the US?

Considerably less then 10 grand

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post #25 of 26 Old 12-08-2010, 09:06 AM
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Quote:
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So what is the going rate for an Isco 3 in the US?

If you want to do "street price" discovery, please do that outside of AVS.

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post #26 of 26 Old 12-09-2010, 05:35 PM
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Quote:
Originally Posted by taffman View Post

Based on this there is absolutely no question in my mind that I would settle for a prism based anamorphic lens. I will stay with zooming until I get drunk enough to squander $10,000 on an Isco 111 !

I own an H-FE1500 and while I prefer my Schneider the 1500 is very sharp. I could see pixels on the screen. The only issue I have with prism lenses is reflections out the input of the lens. I don't lose much light but I see almost nothing with the Schneider.
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