My time spent with Prismasonics new HD-5000R

So is this quite comparable to an ISCOIII or Schneider, or do you get a substantial performance increase when moving up to those units? Was planning on using with a SIM2 C3X 1080p 3 chip.
Also, 2.35:1 or should I order 2.40:1?

If you buy the cylindrical lens, your going to need a 2.37:1 screen where
1.7777777 x 1.3333333 = 2.3703702. Technically, that would be the correct AR for all 1.33x stretch lenses, but if you have out board video scaling, you can alter the out put to suit a 2.40:1 when using a varible stretch lens like the Prismasonic HD5000. Having seen one of these in action, I agree with Alan, they are razor sharp corner to corner with no CA.

In the cinema, the AR is actually 2.39:1 yet we seem to know this as 2.35:1 which I am assuming is more to do with "market rounding" than actual AR...

Mark

Alan,

In your review you indicated you used Prismasonic's own curved screen for your testing. Do you feel that with the reduced geometric distortion of this lens, a curved screen is still worthwhile, or do you think the distortion at this point is so low that a flat screen would maintain the best geometry?

Not sure what Alan found, but the one I got to test was running infront of a BenqW20000 at TR of about 2.2:1. I could see pincushion, but it so small (less than 1/2" on a 10' wide screen) that I considered a flat screen to be quite OK...

Mark

Think about it...

The reason Prismasonic introduced a curved screen in the first place is because a flat screen exhibits distortion. The curved screen was built to eliminate distortion.

If a curved screen presents 99% perfect geometry, how could a flat screen possibly do better?

I was under the impression that the curved screens were introduced to combat the geometric distortion often caused by the anamorphic lenses. If we assume the distortion is either extremely low or non-existent on this lens, then in theory a curved screen shouldn't really be needed as there won't be anything to correct, and in fact a curved screen could skew things in the other direction if that were the case.

I'll admit I'm still iffy on a lot of the details of both projectors in general as well as anamorphic lenses and the overall impact of both, so my understanding could indeed be off. But that's why I asked!

I'm considering going with this lens before the sale runs out in a few days, so I just want to understand what the impact of ordering this lens might have on the screen for me.

Yes it does work to correct pincushion, but the exact amount of curve will be projector/lens/TR dependant. You can't just assume one radius for all cases...

Mark

Papajin, what I was trying to do was to get you to think for yourself.

Ask yourself this question: If there is no distortion on the new Prismasonic lens, why does Prismasonic itself market a curved screen to combat distortion, presumably for its own lenses?

The distortion is "extremely low or non-existent on this lens" only because the demo was performed using a curved screen. On a flat screen the distortion all comes back again.

There are two principal types of distortion associated with expansion anamorphic lenses: geometric and pincushion. Pincushion you know about: the height at the edges is greater than the height at the center. Grid distortion is when a rectangle of nominal size is greater in width at the edges than the same rectangle would be at the center. For example, a 1" square, expanded by a 1.33x anamorphic lens should be 1.33" everywhere on the screen, in theory. But in fact it will be slightly smaller in the center and slightly larger at the edges, say 1.31" and 1.35" respectively. This difference in size of the rectangle between the center and the edges is grid (or "geometric") distortion.

To a large extent, both are associated with the simple fact that the distance from the projector's lens to the edges of the screen is longer than the distance to the center of the screen. The longer the distance, the greater the magnification. The greater the magnification, the greater the height and the greater the width of the image. In short, as you move to the edges of the screen, the image is going to get gradually bigger because it's being projected over a longer and longer throw towards the edges.

How to fix this?

Because the addition of an anamorphic lens means that the total system - projector lens and anamorphic lens - now wants to project onto a curved field, we construct a curved screen which rectifies almost all pincushion and grid (or "geometric") distortion. This is what the top photo above represents: a 1.33 stretched 16:9 image with little or no grid or pincushion distortion but only if projected onto a curved screen of suitable radius of curvature. Project the raw image onto a flat screen and you get pincushion and grid (or "geometric" distortion).

Prism designs are ancient in their lineage. Anamorphic prisms go back to the 19th century. Two prisms with a simple corrector lens cannot solve the problem of grid and pincushion distortion on a flat screen, unless the laws of optics have been repealed and re-enacted (which they have not).

The extra corrector lens that Prismasonic have added does not fix either type of distortion. It is there to fix astigmatism, which is most simply expressed as the vertical and horizontal dimensions of the image having two separate focus points. The corrector lens makes these two points the same within a certain "Sweet Spot" range of throws. It is usually a very weak cylindrical lens curved only in the horizontal direction. This is why the new Prismasonic is so sharp, edge to edge. However, the corrector does not fix distortion.

So, finally, in answer to your question, if you use a flat screen expect very little (or no) less distortion between this version of the Prismasonic and the previous version. The new design most likely does not address distortion at all, only focus. The simplest fix for distortion is a curved screen, which is what was used to demonstrate the lens in the photos above (and which Prismasonic manufacture to make their lenses - and any other anamorphic lens, prismatic or cylindrical - look as good as they can be).

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Addenda: there's a second way to fix pincushion and grid distortion. Use a long throw ratio. At long throw ratios (throw/screen_width), say over 3.0, the differential distance between the edges and the center of the screen is much less. Therefore the differential magnifications between edges and center will be about the same... no pincushion, no grid distortion. At long - very long - throw ratios you don't need a curved screen, as the flat screen is a good enough approximation of a short section of a large radius curve.

CAVX (Mark) has listed an experiment he did at a longer than usual throw ratio of 2.2:1 where pincushion on a 10' screen was half an inch. This is "stock standard" pincushion for this throw ratio and screen size. Nothing remarkablly small about it at all. But Mark's experiment proves the point: longer throw ratios equal better distortion performance on a flat screen. If his throw ratio had been 3.0 instead of 2.2 the pincushion would have been 1/4", virtually negligable.

***********

Lastly: Why don't projector lenses induce distortion?

Simple answer: because they have up to 20 individual elements in them to do just this.

An anamorphic lens only has a few elements, and thus cannot correct as well as a custom designed projector lens.

When the Prismasonic lens is touted as a "five element" lens, all this means is that it has two prisms of two elements (cemented together, to fix color aberration) each, plus a corrector lens.... actually three functional "lens groups", not five. Compare this to a 20 element projection lens, with six or more groups of elements, and you may see why distortion is not a great problem with projectors on their own, but is with an anamorphic lens tacked onto the end of them.

**********

Final comment: this has been a short layman's explanation. If you want a longer, more technical one try any reputable optics textbook. Sit down with a pot of coffee and be prepared to read 800 pages of dense mathematics and trigonometry. Otherwise, the above is a reasonable explanation that covers the basics.

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This is true. Perhaps a better way to ask my question is, assuming a longer throw ratio (2+), and this lens, is a curved screen likely to provide any noticeable benefits? For my own room, I'm currently thinking about a 2.35'ish TR to be more specific.

I dunno. Maybe I'm just asking a dumb question. I'm still learning about projectors, and more specifically how an anamorphic lens may impact room design (mostly where to put the projector), projector choice, and screen type.

So what projector are you looking at? The thing TRs and HT projectors is that longer the TR, the further back you have to mount the projector and the less zoom you use. With my Benq at the least zoom (smallest image), I max out at about 2.2. There are some projectors that allow TR to extend back to 2.5, and the only ones I've seen (without a long throw adpator) that could give you 3.0 or better is Panasonic and Epson - both of which are LCD...

Your TR is found by dividing the distance from the screen to the projectors lens (not the anamorphic lens) by the width of the native 16:9 image. As I said with my Benq, I am limited to 2.2 max at the smallest image size.

Remember, TR won't change with screen size as it is proportional. If you increase the screen size with the projector at a given distance, you reduce the TR. If you reduce the TR, you increase pincusion and other goemetry related issues like grid distortion that Aussie Bob speaks about is his very informative post earlier.

So lets start with identifying what projector you want to use...

Mark

I'm leaning towards the Panasonic PT-AE2000U at the moment.

Screen would be 2.40 AR, 120" x 50" more than likely. This will give us a 88.9" x 50" 16:9 screen. Screen to projector lens distance would be approximately 17.5 feet or 210 inches. That means a TR around 2.36 if my calcs are correct.

That's the current plan. I am waiting to see what CEDIA brings to the table, however.

Just ordered mine, first CIH set up.

I just ordered the manual version.

Papajin, I'm in a very similar situation to yours. Considering a 110" x 46" screen (which by my calculations is 82" x 46" in 1:78 format). Looking to mount the PJ somewhere in the 15 feet to 17 feet range.

I figure my throw ratio to be in the 2.19 to 2.48 range. I am hoping that the pincushion effect is minimal at these numbers.

I am considering the Panasonic AE2000U and the JVC RS2. The Panasonic would allow a flush ceiling mount but the JVC is less forgiving and will likely need an extension rod from the ceiling. Top of the screen will be at 24" down from a ceiling height of 9 feet.

I'd like to wait for CEDIA but wife wants the project finished yesterday.
OTOH, new products introduced at CEDIA will likely not ship until November. Panasonic have introduced a new model every year at the show for the past 6 years. From what I've read, JVC are not planning a new model, except the 4K ones.

Decision time.. what to do? Expect the finance minister will prevail and I'll end up buying the PJ very shortly.

BTW, a BIG thanks to Ausssie Bob and Mark for all their insights. The more I learn about this hobby/sport/disease the more I realize how much I don't know!

Any comments on my thoughts would be most welcome.

~hemster

Did you consider your lumen output from the RS2 at that distance? Not sure what sort of ambient you might have, but it may be worth a second thought if you haven't run the numbers yet. Keep in mind of course that the lumens will drop with bulb age as well.

Some might consider what the way I'm doing things backwards (fairly expensive anamorphic lens, and relatively cheap projector), but the way I figure it, a good anamorphic lens is something you'll likely buy once and use from projector to projector, whereas the projector is likely to be replaced from time to time. Of course this theory doesn't really take into account the fact we could at some point see anamorphic lenses become obsolete, but that's something that's hard to guess at the whens, hows, and ifs right now. I figure if I get at least 10 years out of the lens, I'll have gotten my money's worth.

Addendum:

Just ran the numbers on projector central using their calculator and according to them the Panasonic and JVC RS1 would have an image brightness of 18fL, while the RS2 would be 15fL. Not really sure how these numbers are arrived at seeing as the Panasonic is on paper at least a brighter projector.

The Panasonic's figures are based on a combination of "best cases": brightest picture setting, widest iris, no "cinema" optical filter in line, etc.

The JVC does not have an iris, or an in-line filter for "cinema" modes. What you see is what you get with the JVC, no tricks, no enhancements. Regular use will produce those figures. The JVC's figures are honest and essentially uncomplicated by fine print.

While the Panasonic's figures are not dishonest as such, they refer to modes of usage which are not routine.

Set the two projectors side by side, fairly set-up in equivalent modes of operation (and forget the hype), and you'll see they are close in brightness.

And then, you'll notice that the JVC has radically better absolute blacks and contrast ratio, both of which make the viewing images with it an enhanced experience.

Thanks for your feedback. I really appreciate it.

My room is a dedicated theater so I will have complete light control over it. I also should have mentioned that I'm considering a screen with 1.3 gain which will hopefully give me sufficient lumens.

I do agree that a good lens in an investment but the projector can be replaced. However it'll be a while before the wifey would agree to replace the projector. I'm thinking that I'll be happy with either projector but if I get the JVC then I won't be thinking about a trade up for a few years as I await some new technology.

Then again, if I get the Panny, I can put the savings (over the JVC) toward a scaler. With the JVC, I wouldn't need a scalar as it has the Gennum processor. I know I can set the colour profiles on the JVC with a scaler but I can also make do by the PJ's adjustments.

This choice is really tough and I don't mind telling you, it keeps me up at night agonizing over it.

I don't know why you want a scaler with the Panasonic AE2000. It already does an excellent vertical stretch, as does the RS2. Both built-in. Both on HDMI and component.

I hope you are feeling better now?

I was thinking about leaving the lens in place all the time. So a scaler would allow me to do this as I understand.

Yeah, that's what I was thinking. I thought throwing up salsa and burritos was bad enough...

Anyway, I think this design is superior to the sled versions. This is something I can use in client's homes that don't want a lot of visual bulk (sled) and automation.