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Anamorphic Lens...

Discussion in 'Projectors, Screens & Video Processors' started by cyberheater, May 25, 2005.

  1. cyberheater

    cyberheater
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    I've just purchased an anamophic lens

    [​IMG]

    To try out on my BenQ PB6100 800x600 DLP PJ.

    I'm looking forward to converting it to 16:9 but using the full vertical resolution of the panel which should reduce SDE and increase brightness and also get rid of the faint dark grey boarders top and bottom.

    I'll be picking it up from the post office tomorrow.

    I just need to figure a way of attaching it to the front of the PJ (now where did I put my gaffer tape).
     
  2. GrahamMG

    GrahamMG
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    Urm..... The only way you get true 16:9 is to have a true 16:9 panel, if you use your current full vertical res, the picture will be cropped at the sides when displaying a 16:9 native image.
    Sorry but I'm not sure what you are trying to achieve here...
     
  3. Peter Parker

    Peter Parker
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    Graham,

    If it's like the various anamorphic lenses available (including the one I had on my HT100), it will opticaly squish the image down to the correct ratio (or stretch it sideways like some do).

    Here's a link to Prismasonics site for more info:

    http://www.prismasonic.com/finnish/

    By displaying a 4:3 anamorphic image directly from a DVD player, you'll be seeing tall and skinny people (you sucking eggs yet?), and using all available pixels, so with the lens in place, you'll have no light spill, more brightness (if the lens is good) and better resolution.

    Cyber,

    Looking forward to the results - what type of lens is it? A cinemascope one or something meant for a true cinema projector? I want pics!

    Gary.
     
  4. cyberheater

    cyberheater
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  5. Peter Parker

    Peter Parker
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    What's the diameter of the lens glass? The anamorphic lenses I've seen for digital pjs have all had quite a large flat surface area, so I'm curious how well this one will work.

    This one keeps the image height but stretches it sideways, so you'll have to move the pj closer to fit the screen unless your zoom can accomodate it. Have you tried it up against the 6100 yet? That's a bargain price though so it's not a great loss if it's not suitable. If only all anamorphic lenses were that cheap. :)

    Gary.
     
  6. cyberheater

    cyberheater
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    I'll be picking it up today so will find out about dimensions etc...

    It's gonna be a long work day that's for sure.
     
  7. GrahamMG

    GrahamMG
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    OK Gary I'm listening (and sucking), how do you get a 4:3 anamorphic output from a DVD player, I sort of understand what your saying but it doesn't really compute in my head yet. I've fitted such lenses to an Epson LCD 4:3 and they are very big buggers (front element well over 6 inches across) and bloody expensive (well over £4k...) and frankly the result was not that great but did stop the panel light spill. I just don't see how you can improve resolution when all you have to start with is 800 x 600 pixels as that is all the panel can provide. Be gentle on me it is early.....
     
  8. Peter Parker

    Peter Parker
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    lol,

    Morning Graham. :)

    OK, as you know, basic DVD resolution is 720 x 576 for the image, so a 16:9 ananmorphic DVD will fill that and the image will look like it's stretched upwards (as stored on the DVD). The DVD player will send that to the display as either a letterboxed image of the correct ratio, with black bars top and bottom, or it will send it unaltered to the display, for the display to manipulate accordingly and make it look correct.

    The 4:3 pj will scale that up to 800 x 600 so all of the panel and light output is used, but the AR is wrong. Normaly you would get the pj to remove lines of resolution so that you end up with an image using 800 x 450 lines, and the correct aspect ratio, but the pj will be projecting black bars as well. So far you know all that (and much more) but I thought I'd say in case somewone else was curious. :)

    Now, if you let the pj display the stretched image as 800 x 600 with an incorrect ratio, you're using all lines of resolution available in the pj, and all of it's light output, since it's projecting only image, and not black bars. By attaching the lens, it opticaly squishes it down, or optically stretches it sideways (depending on the lens) so that the ratio is now correct. By doing this, you're using all the pjs lines of resolution and all of it's light output to display the image. If the lens is good, you will gain brightness as well, if it isn't it will remain about the same. Either way you will lose the light spill (if you see it) above and below the image that may appear as dark grey bands.

    Hope that makes sense. The Prismasonic link should be of some help, and avsforum has had the Panamorph lens available for a few years now, and is very similar to the Prismasonic lens. The NEC HT1000 had its own Optimorph lens which fitted onto its lens rather than mounted independantly in front of it. Initialy they were around $1000 or more, but prices have dropped considerably since they've become more common. I bought mine for £300 and sold it for £210 so they can be got quite cheaply if you look around.

    It doesn't stop there either. Some use an anamorphic lens on their 16:9 projectors for 2.35:1 movies. Either the pj, the source or a scaler inbetween will stretch the 2.35:1 movie up so that it fills the 16:9 display, then use the anamorphic lens to squish it down or stretch it sideways to the correct AR again. It allows the use of the full panel and light output, and removes the black bars above and below, so it still has it's advantages with true 16:9 projectors.

    Gary.
     
  9. GrahamMG

    GrahamMG
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    Hi Gary.
    OK, I get all that, can't this be done electronically just as well? I know my scaler and pj combination can be set to get a full screen 16:9 image from a 2.35:1 source but I thought I'd loose picture information somewhere along the line, I just hadn't considered that an optical way might be better/worse? Mind you electronically is easier to turn off and on?

    Good stuff, nicely put.
     
  10. Peter Parker

    Peter Parker
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    Hi Graham,

    if you mean stretching up 2.35 material to fit a 16:9 display, then yes it has to be done electronicaly in the source, scaler or pj. Typicaly pjs can't do this (some can but not many as far as I know), so an external scaler (or an HTPC) is the most common way.

    You shouldn't be losing picture information, but with 2.35 stuff, the scaler will have to invent data to fill the lines that aren't there from the source. That's happening to some degree with 720 displays anyway, as 576 and 480 sources have to be scaled in both directions and data interpolated to make it fit into 720. If you're not seeing anything detrimental as a result of this, then the chances are stretching a 2.35:1 movie to 16:9 will be equaly good.

    Opticaly is the only way to use all the panel resolution and lumens and to remove the black bars. Using an anamorphic lens is better if the lens is good, and most are. The only downside might be some barrel distortion (some anamorphic lenses have it to some degree, and others don't but it can be lost in the screens black border). If you want to 'switch it off', some lenses are hinged and can be flipped out of the way, and some have a sliding bar so that it can be slid out of the way.

    Gary.
     
  11. cyberheater

    cyberheater
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    Which is key here. You get to use the whole panel resolution which gives you 33% percent improvement in resolution and 20% increase in brightness.
     
  12. cyberheater

    cyberheater
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    Gary,

    Your not going to believe it. I've just bought a Prismasonic from ebay at 200 quid cause I figured if i'm going to down this route. I might as well do it right.

    It had only just been listed.

    Mine is the V-200.

    What is your experience of it?
     
  13. Peter Parker

    Peter Parker
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    I've not seen one of those, but they're meant to be pretty good. Excellent price for one of those, especialy when you consider how much they were going for a few years ago. It'll be an interesting comparison betwen them.

    Gary.
     
  14. cyberheater

    cyberheater
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    Well. I had a go at installing the anamorphic lens and have run into 3 problems.

    1/ I can't get the lens near enough to the light source (it's actually touching the glass) which causes the edges of the screen to be masked out by the tube of the anamorphic lens.

    2/ The anamorphic is severe. It easily stretches is out to at least twice the width of the original picture. I was hoping for less then that. It's too wide.

    3/ A lot of barrel distortion.

    It was fun and worth a go but not worth taken a piccie of.

    At least i've got my Prismasonic to look forward to.
     
  15. Peter Parker

    Peter Parker
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    Can you zoom the image to it's smallest so that the projected beam is at it's narrowest, or have you already tried that?

    Would it be possible to cut away the thread of the lens so that the glass is nearer to the pj or is it not as simple as that?

    Worth a try and at that price all the same, and not a great deal of money to lose - worth it for the experiment/learning experience IMHO.

    The Prismasonic will not dissapoint after this 'trial run'. My only issues with the anamorphic lens I had were that I had to move the pj closer to the ceiling as the projected image was now dead center to the 4:3 image it would be projecting, and my 16:9 screen was too low. I couldn't move it any higher, so the pj had to go flush to the ceiling, and also further back so that the bottom corners of the light beam weren't fouled by the lens housing (similar to the cheap lens). It was a noticable improvement over standard, but I didn't get round to moving the pj further back before I bought the optoma H77, so that was a failed experiment too. :)

    Anamorphic lenses are an improvemnet for any 4:3 pj IMHO and at £200 are almost a no-brainer.

    Gary.
     

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