Video processor versus lens sled: pros and cons - AVS | Home Theater Discussions And Reviews
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Old 05-17-2010, 07:35 AM - Thread Starter
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Hi all,

I have an ISCOIII and Cineslide. I'm waiting on Cedia this year to decide on a projector, but leaning heavily towards a JVC HD990.

Although I had originally thought I'd move the lens back and forth, depending on source, I'm now considering whether I should just leave it in place and use a video processor, such as a Lumagen XE. Sale of the Cineslide would go towards the Lumagen, so it's not so much a matter of money. I'm after convenience for the family and ultimately, best picture quality.

I'd be keen to hear and understand the pros and cons of using a video processor versus using an auto sled.

Mainly blu-ray adventure movies (tend to be in 2.35) and PS3 games.

Cheers,

Chris
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Old 05-17-2010, 08:41 AM
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Well I use a Kino linear Sled with my lens and when watching 16x9 material I prefer to remove the lens than have to scale it to 4:3. If you have a curved screen than I agree lens should stay in place.

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Old 05-17-2010, 04:05 PM
 
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I have a hard time believing a processor scaling 1920x1080 down to 1440x1080 could possibly look better, or even as good as an optical scaling of the 1:1 mapping (but this depends on seating distance).

The convenience factor I might understand, but you said ultimately "best picture quality", so I don't think there's a comparison here.

Of course, if convenience is the deciding factor, one touch instant AR switches and no lens movements would be quite an advantage. Can the Lumagen auto-detect 1.78/1.85/2.35 (black bar detection) and automate the proper scaling so it's hands free?

This method, you would have identical resolvable resolution from a certain perspective- 1440x1080 and 1920x810 are spot on in total pixel count.

Bottom line I guess if flexibility and convenience are deciding factors, go with the Lumagen. If best picture quality wins, keep the sled.
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Old 05-17-2010, 04:49 PM
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USE: It depends on who operates the system. If it was just himself, then given he has a flat screen, he could move the lens in and out of the light path. If his wife and kids are to use it, then it is best to leave the lens in place with a simple one button push on the remote .

PQ: I do leave my lens in place because of the following:
Same pixel density for all ARs
Same calibration setting for all ARs
Same Brightness levels for all ARs
Same geometry for all ARs due to the curved screen.

As for scaling 1920 down to 1440, yes it does remove H rez, however the lines removed are every fourth line, so the amount of detail is too small for the eye to resolve anyway based on single pixel display lines at 1920 x 1080 rez. The most noticeable thing I have found over the years is a brightness shift. The amount of added (restored when A-lens removed) detail is trivial in the scheme of things.

My suggestion to Chris1971 is to simply watch both lens in/lens out and make an informed decision based on what you see, not those around you. In the end, with his level of system, he is going to want a VP anyway, so why should that VP not be used to control AR as well?

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Old 05-17-2010, 08:04 PM
 
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Quote:
Originally Posted by CAVX View Post

My suggestion to Chris1971 is to simply watch both lens in/lens out and make an informed decision based on what you see, not those around you. In the end, with his level of system, he is going to want a VP anyway, so why should that VP not be used to control AR as well?

I was going to suggest that as well. Makes this decision easier- just add the Lumagen to what you have now, and enjoy the best of both worlds.

If it makes it easier, the scaling in the Lumagen should be able to do much better at the standard 1.33x vertical stretch needed for 2.35 content with the lens, and you will enjoy slightly better PQ with those films because of that.

I wonder at seating distances between 2.0x and 2.4x screen height, if you took an average HD950 with a Lumagen doing the scaling, and an HD990 with the PJ's internal scaling, which end result would be preferred to those who didn't know which was which.
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Old 05-17-2010, 08:11 PM
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Quote:
Originally Posted by LilGator View Post

The convenience factor I might understand.

Since he already has a motorized sled, isn't the convenience factor (i.e. single button push for AR change) the same as a permanent lens install?

If the above is true, then using the full 1920x1080 pixels will give better picture quality vs downscaling to 1440x1080. But it may not be noticeably better. Should be easy to verify.
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Old 05-17-2010, 08:48 PM
 
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Quote:
Originally Posted by ilsiu View Post

Since he already has a motorized sled, isn't the convenience factor (i.e. single button push for AR change) the same as a permanent lens install?

If the above is true, then using the full 1920x1080 pixels will give better picture quality vs downscaling to 1440x1080. But it may not be noticeably better. Should be easy to verify.

I guess it really is. Cineslide is about a 1-second adjustment right? VP would be instant, but there isn't much of an advantage there.

If it did auto-detection based on black bars, that would be foolproof for the family.

I think the advantage lies in the external VP being a better scaler for any type of sources, even 'scope films- so he'd have a PQ advantage, and the flexibility of lens or no lens with 1.78/1.85 material.

Of course it's the most expensive option, as you'd keep the slide. I'd probably order the options this way:

1. Add an external VP.
2. Keep the slide.
3. Sell slide, add VP.
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Old 05-17-2010, 10:11 PM
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Given that he said that we would sell the Slide to fund the VP purchase and given all of the pros and cons given, maybe a manual slide would work here to allow him (not his family) to move the lens should he wish to do so.

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Old 05-24-2010, 02:34 AM
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Having used this method, I see no loss of resolution at all. From
a foot from the screen the only difference I can discern is the shape of the pixels. As stated many times here, loss of res on the horizontal doesn't have the same effect as on the vertical plane. Speaking from experience the only problem I have is the lighter pillarbox as I don't use masking. It's really not an issue.
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Old 06-14-2010, 03:54 PM
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With a film projector you really don't have a choice as the aspect ratio is different between 1.85 and 2.39 formats. With a digital projector the advantages of leaving the lens in place is the relative brightness stays the same whether the format is 2.39, 1.85 or 1.33. Yes there is video processing but mentioned in a AVS forum the compression of a Blu-Ray is so high (50-1) was an example the 33% vertical expansion is not really noticed on film material. Now if the application is video computer graphics yes there is a improvement with removing the lens for a 1:1 bit mapping of the projected image. For example one should set their computer video card to the same resolution as the native resolution of their monitor for the sharpest image. For me I would rather leave the lens in place and keep the same relative image brightness when switching to different aspect ratios. There is no wrong answer, it is your personal preference.
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Old 06-14-2010, 04:03 PM
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Quote:
Originally Posted by CRGINC View Post

Now if the application is video computer graphics yes there is a improvement with removing the lens for a 1:1 bit mapping of the projected image. For example one should set their computer video card to the same resolution as the native resolution of their monitor for the sharpest image. For me I would rather leave the lens in place and keep the same relative image brightness when switching to different aspect ratios. There is no wrong answer, it is your personal preference.

Just an FYI, I've been playing with streaming HD and found that there is a "scale to 16:9 TV) built in and it therefore outputting a scaled image made up of 1920 x 1080 pixels. The projector gets set to "real" mode for a 1:1 mapping of the program it is being sent, so therefore any possible scaling artifacts (and I don't see them with the BenQ anyway) is removed.

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Old 06-16-2010, 03:55 PM
 
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Quote:
Originally Posted by CAVX View Post

Just an FYI, I've been playing with streaming HD and found that there is a "scale to 16:9 TV) built in and it therefore outputting a scaled image made up of 1920 x 1080 pixels. The projector gets set to "real" mode for a 1:1 mapping of the program it is being sent, so therefore any possible scaling artifacts (and I don't see them with the BenQ anyway) is removed.

If the source isn't truly 1920x1080 pixels, then there will still be scaling artifacts.

It's just the same when you use a HTPC to feed 2.35 Blu-ray's anamorphically 1920x1080 to your projector. Yes, you are providing 1:1 to your projector, but scaling still occurs!

You've just moved the scaling from your projector to your HTPC. Ideally of course, you want the best scaler you own to be doing the job, and only one scaling operation. So if your HTPC video card (or software scaler) does better than your projector, why not.

But just because your projector is fed 1:1 pixel mapped, doesn't mean scaling artifacts have been eliminated in the chain.
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Old 06-16-2010, 04:09 PM
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Quote:
Originally Posted by LilGator View Post

If the source isn't truly 1920x1080 pixels, then there will still be scaling artifacts.

It's just the same when you use a HTPC to feed 2.35 Blu-ray's anamorphically 1920x1080 to your projector. Yes, you are providing 1:1 to your projector, but scaling still occurs!

Yes I get that. What I am saying is that scaling artifacts a projector might introduce is now removed. The projector can then scale that image 1:1. EG: I've seen a "ripple effect" on a JVC HD550 (RS15?) with a certain title that I have not seen on my BenQ W5000 for the same scene. This "ripple" was not there on the JVC when playing the scene back in letter boxed format (V-Stretch OFF), hence I would say that was a scaling artifact.

Quote:


You've just moved the scaling from your projector to your HTPC. Ideally of course, you want the best scaler you own to be doing the job, and only one scaling operation. So if your HTPC video card (or software scaler) does better than your projector, why not.

Exactly.

Quote:


But just because your projector is fed 1:1 pixel mapped, doesn't mean scaling artifacts have been eliminated in the chain.

Given a chain is only as strong as the weakest link, if one can change out the weaker link for a better one, then it has to be seen as an improvement.

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Old 06-18-2010, 09:41 AM
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After spending hours comparing test material and movies, I've come to the conclusion that I can't see a difference between the two. It actually looks a little better with the lens in for 19x9 on sharpness patterns due to the documented focus issues on the left side of screen with the Benq W5000. I've yet to run numbers for contrast with and without lens in but it appears close.
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Old 07-11-2010, 06:43 PM
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Quote:
Originally Posted by coolrda View Post

After spending hours comparing test material and movies, I've come to the conclusion that I can't see a difference between the two. It actually looks a little better with the lens in for 19x9 on sharpness patterns due to the documented focus issues on the left side of screen with the Benq W5000. I've yet to run numbers for contrast with and without lens in but it appears close.

coolrda,

Really nice theather. Reminds me of my own. It has a 9' screen almost wall edge to edge. The room size is about 9'7" or so wide and almost 20' deep. When I built it projectors were only 4:3. It is fine for personal viewing but not for a crowd.
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