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post #1 of 9 Old 06-25-2016, 04:00 PM - Thread Starter
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Conversion Lens and 4K

Hello,

I have been considering creating a home theatre for a number of years now. I have read many threads in the AVS Forum during this time and will continue to do so, but I am going to need some advice.
My first concern at this early stage is knowing whether or not what I am considering is worth doing (regarding projector and screen).

I do not have a projector yet.
I am going to take things step by step, so before getting one I would first like to know if it would work in my room.
To get a large screen size to work in my room, I would definitely need a conversion lens.
However, I do not know if a conversion lens will maintain the original quality of a 4K or pseudo 4K projector (like JVC e-shift) with a 4K source (like UHD blu-ray).
Help with this will aid me in deciding if I can proceed with getting the projector and conversion lens.

While things may change, the projector that I am currently considering is the JVC DLA-X750R (aka DLA-RS500U).
The JVC X750R has a throw ratio of 1.4:1 to 2.8:1.

My room is small, only about 12 feet long (closer to 11’ 10”) and roughly 94” high. The front and back walls have framing over heating duct work that extends about 7” down from the ceiling and about 26” into the room, so the ceiling height in these areas is about 87”. I will try to post a rough drawing.
If the projector is close to the back wall and the screen is tight against the front wall then I am guessing that the distance from projector lens to screen would be around 10 feet.
I think that a 2:35:1 or 2:40:1 screen that is about 110 inches wide (120 inches diagonal) or 115 inches wide (125 inches diagonal) would be a good size (but this could change once I get a projector and test the image size for preference). For now, I will consider these sizes as ideal.

My biggest question:
1) Based on the above info, how will the Navitar HDSSW08 and HDSSW065 conversion lenses perform regarding maintaining the video quality/sharpness coming out of a 4K projector with 4K sources?

Also:
2) Are there conversion lenses by other manufacturers that are worth considering?
I would especially like to hear from those with first hand experience (if there are any) using such a lens with a JVC (or other) projector.
I am not considering an anamorphic lens because from what I remember reading, the affordable ones would not work well from this distance (even with a curved screen).

3) Is there any other issue with using the conversion lens when the projector is at the closest/maximum zoom (i.e., projector is located as close to the screen as possible vs. farther away) as in my situation? For example, any issues with vignetting, distortion, chromatic aberration etc... ?

I would like to try it out and see for myself regarding the sharpness quality (not to mention other quality factors such as maintaining colour fidelity).
However, I need to try the lens and projector combo first in order to decide an appropriate screen size.
The problem with this is if I do not have a screen when I try the lens then I can not determine how good the lens is.

Thank you for your assistance.
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post #2 of 9 Old 06-27-2016, 05:12 PM
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Quote:
Originally Posted by neverwhere View Post
My biggest question:
1) Based on the above info, how will the Navitar HDSSW08 and HDSSW065 conversion lenses perform regarding maintaining the video quality/sharpness coming out of a 4K projector with 4K sources?
These Navitar lenses are first class glass. I had paired a Navitar HDSSW065 lens with a JVC RS4910 for a brief time and only in a setup on a table with the projector at 0% lens shift and with the lens almost perfected aligned to the center image axis. The focus uniformity was excellent. From what I recall there was minimal-to-no chromatic abberation at the image extremes with my nose to the screen. Overall, I was amazed at the quality of the glass and would expect it to work extremely well for 4K too.

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Originally Posted by neverwhere View Post
[LEFT]Also:
2) Are there conversion lenses by other manufacturers that are worth considering?
Not that I'm aware of.

Quote:
Originally Posted by neverwhere View Post
3) Is there any other issue with using the conversion lens when the projector is at the closest/maximum zoom (i.e., projector is located as close to the screen as possible vs. farther away) as in my situation? For example, any issues with vignetting, distortion, chromatic aberration etc... ?
For the HDSSW065+JVC (with using 0% lens shift with the Navitar about as close to the primary lens as possible) my measurement was that I was able to achieve a throw ratio of 1.02 without vignette and for 2.35 material a throw ratio down to 0.96 without vignette of the 2.35 portion of the image. If you use lens shift you need to align the lens to the image axis which causes the Navitar lens to be further from the primary lens which will further reduce your achievable effective throw ratio (sorry, I did not measure for this case).

I did not detect any issues in using the extreme end of the lens before vignette.


One point to be aware of is that when you use the Navitar lens your effective lens shift is also reduced by the same multiplier (0.65 or 0.8). Practically speaking, for the JVC with 80% lens shift and HDSSW065 at best you can position the projector at the top of screen height (80% * 0.65 = 52%). For my room this was the biggest reason that I sold my Navitar lens, since besides it being closely mounted above my head it also would block line-of-sight to my top-middle atmos speakers for those not sitting directly below the projector.

I continue to use a first surface mirror for my 12'-wide by 10'-deep room with 2.35 100"-wide screen. I have plans (but no time for now) to build a 115"-125"-wide screen and use a combination of the mirror and my ISCO 1.42x A-lens (larger than the IIIL but non-1.33x expansion factor) plus Lumagen 2020 or maybe a Navitar HDSSW08 (for better height above screen and to avoid pincushion from the A-lens but at cost of overspill lumens).
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post #3 of 9 Old 06-27-2016, 05:56 PM - Thread Starter
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Quote:
Originally Posted by jjcook View Post
These Navitar lenses are first class glass. I had paired a Navitar HDSSW065 lens with a JVC RS4910 for a brief time and only in a setup on a table with the projector at 0% lens shift and with the lens almost perfected aligned to the center image axis. The focus uniformity was excellent. From what I recall there was minimal-to-no chromatic abberation at the image extremes with my nose to the screen. Overall, I was amazed at the quality of the glass and would expect it to work extremely well for 4K too.).
Good to hear. Sounds promising quality-wise.


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Originally Posted by jjcook View Post
For the HDSSW065+JVC (with using 0% lens shift with the Navitar about as close to the primary lens as possible) my measurement was that I was able to achieve a throw ratio of 1.02 without vignette and for 2.35 material a throw ratio down to 0.96 without vignette of the 2.35 portion of the image. If you use lens shift you need to align the lens to the image axis which causes the Navitar lens to be further from the primary lens which will further reduce your achievable effective throw ratio (sorry, I did not measure for this case).

One point to be aware of is that when you use the Navitar lens your effective lens shift is also reduced by the same multiplier (0.65 or 0.8). Practically speaking, for the JVC with 80% lens shift and HDSSW065 at best you can position the projector at the top of screen height (80% * 0.65 = 52%). For my room this was the biggest reason that I sold my Navitar lens, since besides it being closely mounted above my head it also would block line-of-sight to my top-middle atmos speakers for those not sitting directly below the projector.
Interesting.
I did not give any thought to lens shift.

It seems that at maximum vertical lens shift with the projector aligned near or at the top of the screen that the picture quality with Navitar lens in place is still as good as with no lens shift (projector at middle of screen)?

Is it difficult to properly align the Navitar lens when using a lot of vertical lens shift?
I have never had a projector, nevermind having tried to place another lens in front of one, so I have no experience with this.

Is special equipment needed to attach the Navitar lens to the projector if using a ceiling or wall mount?

How far out into the room from the projector are your top middle atmos speakers that they are still blocked by the conversion lens? And how high are your speakers relative to the projector and lens?
I was planning on doing atmos/DTS-X for the audio in my room, so this could potentially be an issue for me too.

Thanks for all the useful info!

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post #4 of 9 Old 06-28-2016, 09:44 AM
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Quote:
Originally Posted by neverwhere View Post
It seems that at maximum vertical lens shift with the projector aligned near or at the top of the screen that the picture quality with Navitar lens in place is still as good as with no lens shift (projector at middle of screen)?
There should be no picture quality difference for the case of using lens shift. Again the lens simply needs to be aligned along the central axis of the projected image. An open question is if when using lens memory if the "source point" of that axis within the projector moves significantly when changing from projecting for 16:9 to 2.35; if it does end up in a different location and you're trying to use the full magnification of the lens then you might have some vignette. As far as I know since the LCoS panels are not moving and just the lens you are probably okay but just want to mention it as a possible hiccup that could otherwise require a dynamic lens mount to move the Navitar (of course you could consider only using the Navitar for projecting 2.35 and so move it out of the way just like an A-lens).

Quote:
Originally Posted by neverwhere View Post
Is it difficult to properly align the Navitar lens when using a lot of vertical lens shift?

Is special equipment needed to attach the Navitar lens to the projector if using a ceiling or wall mount?
Assuming you have a mount for the lens that allows for the required 3 degrees of freedom (2 translational, 1 vertical rotation), no.

You attach the lens similarly to an A-lens, where either you get a metal plate attached to the projector that juts out over the front to attach the lens mount or you attach it to an independent ceiling mount. I don't have a simple solution to suggest, this may require some DIY of at least sourcing parts from camera/telescope lens mount parts as its unclear to me if Navitar has a mount solution for the 0.65x lens, their webpage is unclear on this point.

Quote:
Originally Posted by neverwhere View Post
How far out into the room from the projector are your top middle atmos speakers that they are still blocked by the conversion lens? And how high are your speakers relative to the projector and lens?

Thanks for all the useful info!
My ceiling is 9' high and the speakers (Triad InCeiling Gold Omni/SE) are in-ceiling with a 45-degree baffle pointed toward the MLP in the center of the room; they each are approximately 5 feet laterally from the MLP and aligned with my one row of seating. It is the projector not the lens blocking the speakers; if the projector is mounted at about 3' from the ceiling (~2' from head height) and above the one row of seating (along the rear wall) the ceiling speakers are blocked for the two seats on either side of the center -- which I often end up in when casually seated with the family.
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post #5 of 9 Old 06-28-2016, 01:59 PM - Thread Starter
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Assuming you have a mount for the lens that allows for the required 3 degrees of freedom (2 translational, 1 vertical rotation), no.

You attach the lens similarly to an A-lens, where either you get a metal plate attached to the projector that juts out over the front to attach the lens mount or you attach it to an independent ceiling mount. I don't have a simple solution to suggest, this may require some DIY of at least sourcing parts from camera/telescope lens mount parts as its unclear to me if Navitar has a mount solution for the 0.65x lens, their webpage is unclear on this point.
Finding a mount for the lens might prove to be difficult.
A quick search has turned up nothing, but I will keep trying.

A DIY is not ideal as I have limited ability and little free time. I doubt I would even be able to find an installer with experience with this lens since it is a small market application (no home theatre store rep or installer that I have talked to so far has even heard of a conversion lens for this purpose).

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post #6 of 9 Old 07-01-2016, 07:10 AM
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Quote:
Originally Posted by neverwhere View Post
Finding a mount for the lens might prove to be difficult.
A quick search has turned up nothing, but I will keep trying.

A DIY is not ideal as I have limited ability and little free time. I doubt I would even be able to find an installer with experience with this lens since it is a small market application (no home theatre store rep or installer that I have talked to so far has even heard of a conversion lens for this purpose).
If you work out what is needed, then you could hire someone to install.

1. Buy table top stand. https://navitar.com/products/project...ts-and-stands/
2. Buy a couple Chief plates. http://www.chiefmfg.com/Products/CMA105
3. Small block of wood.
4. 1.5" NPT threaded pipe.

1. Measure the distance from ceiling to center of projector lens.
2. Subtract from that stand height to center and thickness of wood block.
3. What you have left is the height of the two plates and the pipe.
4. Have a piece of pipe cut and threaded to match the height needed.
5. If no blocking in place for attachment to the ceiling, then add blocking to ceiling and deduct blocking thickness from pipe length needed.
6. Thread pipe onto plate.
7. Attach wood blocking to second plate.
8. Attach second plate to pipe.
9. Attach stand to wood blocking.
10. Place conversion lens in stand.
11. Hold the whole assembly to the ceiling to find the right location for attachment and mark holes.
12. Drill pilot holes and then bolt the ceiling plate to the ceiling.
13. Adjust lens angle as needed.

If you do the measurements, then it should go together pretty easy.

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post #7 of 9 Old 07-01-2016, 02:27 PM - Thread Starter
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Originally Posted by Mike Garrett View Post
If you work out what is needed, then you could hire someone to install.

1. Buy table top stand. https://navitar.com/products/project...ts-and-stands/
2. Buy a couple Chief plates. http://www.chiefmfg.com/Products/CMA105
3. Small block of wood.
4. 1.5" NPT threaded pipe.

If you do the measurements, then it should go together pretty easy.
Thanks for the suggestion.
According to the Navitar website, the table stand does not fit the HDSSW065 though.

However, I think that a Chief adapter mount like the NAV1 might work (it has a pitch of +10 degrees and -20 degrees).

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post #8 of 9 Old 07-01-2016, 02:48 PM
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Quote:
Originally Posted by neverwhere View Post
Thanks for the suggestion.
According to the Navitar website, the table stand does not fit the HDSSW065 though.

However, I think that a Chief adapter mount like the NAV1 might work (it has a pitch of +10 degrees and -20 degrees).
Sorry, did not pay attention to which lens. Yes the NAV1 will work if you have RPA mount.

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post #9 of 9 Old 07-01-2016, 03:03 PM
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Quote:
Originally Posted by neverwhere View Post
According to the Navitar website, the table stand does not fit the HDSSW065 though.

However, I think that a Chief adapter mount like the NAV1 might work (it has a pitch of +10 degrees and -20 degrees).
Quote:
Originally Posted by Mike Garrett View Post
Sorry, did not pay attention to which lens. Yes the NAV1 will work if you have RPA mount.
I have a NAV1 mount that I briefly used with a SSW08 lens. From my recollection, I do not believe it can even support the weight of the SSW065 let alone the HDSSW065.

You should call Navitar to check if the table stand does support the HDSSW065 (since the page has conflicting statements about compatibility) and also that it is ok for a ceiling mount application.
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