Originally Posted by Aussie Bob II
This is the first time I've seen the ability to precisely focus a cylindrical lens to the millimeter, for perfect sharpness, depicted as some kind of problem or "complication"! And I DO hope John is not saying that a prism lens somehow has a focal range of plus or minus several feet. If he is, then a new principle of optics has been invented: let's call it "universal focus", where near-enough is good enough, and you can just plonk something in front of a projector and it'll be perfect.Just_doesn't_happen, mate.
An image is either in focus or out of it. No grey areas.
What John fails to mention regarding pincushion is that pincushion is not the only distortion that presents in an anamorphic environment. There is also geometric distortion, where nominally square grid divisions will elongate or squeeze depending on their position in the image.
A prism lens, having only plane surfaces (and hence zero degrees of freedom when it comes to correcting optical geometric aberrations), stretches the image much more than 1.33x at the edges, and much less than 1.33x in the center of the image. Sure, the average may come out to roughly 1.33x, but the grid distortion is quite notable, especially with short throw ratios.
The Isco has his problem too, to a lesser extent. Only the Xeit lens has been specifically designed (using additional glass element groups, more than any other lens) to reduce this geometric distortion by a substantial amount.
In response to rather ill-informed comments regarding sealing, the Xeit lens utilizes no less than 5 O-rings to keep dust and moisture out... permanently. You can drop a Xeit lens into a swimming pool and water won't enter it. I don't claim it'll float, but it won't get wet on the inside either. (Note: due to potential electrical hazard, do NOT put your projector into the swimming pool at the same time, especially if it is switched on).
Generally, I do sometimes wonder why (if Panamorph lenses are such superb precision optical instruments) they decline to publish specifications, stating, among other things color purity, ANSI contrast performance, sharpness, pincushion, geometric distortion, ghosting performance, calibration standards, and other factors considered important in assessing quality projection lenses.
Ah, my good friend AussieBob II returns to the forum.
I very deliberately don't make definitive statements saying "my lens is better than yours" or ever bash a competitors product. I see nothing in my posts above that bashes or denigrates ANY competitive lens. If you look through my long history of posting in this forum, I think you will find that I always refer to the Schneider and ISCO as excellent products. I have never seen your lens or a Prismasonic, so therefore have never made comments positive or negative about them. In fact, I will always say "I have never seen XXX lens, so cannot comment about it."
You misrepresent my statement about complication. What I said (and you even quoted me) was "a cylindrical lens needs to be sighted and focused properly for best performance, which usually means a more complicated install." Notice the word "usually," and notice that I said "sighted and focused," not just focused. And please point out to me where I said it was a "problem." In fact, you selectively quote. In the same paragraph of my response, I used the same design feature as a positive! Here I quote myself: "A cylindrical lens allows for focus adjustments, meaning that a lens like the ISCO or Schneider will allow you to fine tune focus for a variety of throw distances. This allows for versatility if you move or change your installation location."
And yes, I am saying that a Panamorph
lens (not a prism lens) has a focal range of a few feet. In the case of the UH480 and DC1, it's 14.5 - 17.5'. You may be incredulous (which, of course, is an argument from incredulity, which is one of the best examples of a logical fallacy there is) but it's true. Within that range, the pixels on even a 4K projector are crisp and sharp. I've seen installs down to 12 feet or up to 20 feet with the same lens where you needed to be literally inches from the screen to see that the pixel focus was slightly softened. Sit at any reasonable distance and the slight softness is unnoticeable. Still, we recommend corrector elements once you get out of that 14.5' to 17.5' throw (and, to be clear, that is not "plus or minus several feet" - it's 3 feet total range, so plus or minus 1.5 feet).
RE: pincushion not being the only kind of distortion in an anamorphic lens, i.e., grid distortion as you move away from the center. This is true. Where I disagree is the use of the descriptors "much" less and "much" more, plus the manner in which you just lump Panamorph in with other "prism" lenses. As I go to pains to point out, a Panamorph is not a simple prism lens, so it is not fair to draw comparisons as if it were.
To the claim, though, that there is more "stretching" of the image out to the sides than there is in the middle. This is true, but I would argue that you are exaggerating the visible effects greatly.
I do, however, agree that it is worse at short throws. A variety of things are worse on all
anamorphic lenses at short throws, so I hardly think we need to focus (no pun intended) on lenses installed outside of their recommended throw ranges and ratios. I would also point out that what is noticeable with a test pattern is not necessarily noticeable with actual video content! If this "issue" were so noticeable, I would think someone on the Forum would have posted about it by now. As you point out, the ISCO exhibits this as well. I have not seen your lens, but for now I take your word for it that you have corrected the grid distortion.
I would really like it if you would take in the entirety of my comments regarding what is a sealed lens or not into account. We HAVE tested Schneider and ISCO lenses, and they are not airtight. And I said this about the XEIT lens:I have never examined an XEIT, so will cop to making a possibly inaccurate statement about the DC1 be the "only" lens that is sealed without ever having tested the XEIT.
RE: why Panamorph does not publish specs regarding its lenses. I don't see what publishing specs has to do with actual performance of the product at all. Any company can publish any optical specs they want. There is no governing body fact checking the specs, so they are essentially useless (1,000,000:1 contrast on a projector, anyone?). The marketing focus at Panamorph is on the experience, not the specs. THAT is what consumers are buying. I've been in the home theater biz since 1983, and I can count on the fingers of one hand how many people have made examining the specs the criteria by which they choose their products. (As an aside, DPI and SIM2 offer high end lens options for their projectors - as did Marantz - yet I have never seen them post any lens specs either.)
That said, if what you are getting at is "how do the lenses actually perform," I am totally with you. As I posted in another thread:I do get frustrated when people just assert something definitive without any hard data to back it up. Until someone actually tests a claim using some kind of blind or double blind standard, it's impossible to make any kind of definitive statement ("high rez audio sounds so much better!" or "product a blows away product b")...of course I expect people to be extremely skeptical of what I report here, since I still occasionally work as a consultant for Panamorph and can very fairly be accused of bias (although almost all of my Panamorph related work has been with CE manufacturers and major studios to get anamorphic video part of Blu-ray and next generation video, a project that - if successful - will benefit everyone, Schneider, XEIT, and ISCO included). I WANT people to be skeptical of my claims, just like I want them to be skeptical of the claim that one design or brand is somehow "automatically" better than another. I encourage a more controlled shootout between the two different lens products, and am happy to let the cards fall where they may when it comes to the results...an ideal shootout would be one that was attended by representatives from all the major brands, with each lens set up properly and under best conditions. At that point their contributions to the proceedings would end, and it would be up to a group of qualified observers to make judgements based upon ideal real world viewing conditions.
Because I am so aware of the dual phenomenons of confirmation and expectation bias, I am skeptical of my OWN findings. We all tend to take in information that supports our own existing conclusions or biases and ignore information that contradicts them. This is a hard-wired tendency that it is extremely difficult for us human beings to overcome. The only way I know of overcoming these tendencies is a test like what I describe above.
Don't you agree, what is actually perceivable to the end user is all that matters? If our lens - and yours, or the ISCO III or Prismasonic, or whatever - performs just as well as another in a situation like I describe above, isn't it fair to say that both products are excellent and worthy of consideration?
This reminds me so much of the discussions over 4K resolution and hi-rez audio. Yes, on paper there are benefits. But can you actually see or hear them? That, to me, is all that matters.
I don't get your attitude at all. I have never bashed or denigrated you or your products in any way, or even cast aspersions on them (which you seem more than happy to do regarding me and Panamorph). In fact, I have reached out to you on several occasions to see if we could be friendly competitors (I say "we" even though I technically do not work for Panamorph) and work together toward supporting anamorphic content from the Hollywood studios, etc, yet have never received a positive response.
It is possible to disagree and still be friendly. I am hardly peddling snake oil.