scanner options?

[Pangolin]

The video with the K bit? Big video, half an hour?

Yes, you can see it here:
http://www.youtube.com/watch?v=BiaM0adidIo

Within the first few minutes I explain what "K" is, and what happens when you make scanners go faster and faster and faster.

Bill

[Pangolin]

Sorry Bill, your original post sounded like that to me.

No problem. Actually this is all pretty complicated stuff. There's bound to be confusion. Actually if you're keeping up at all, then it will show some technical prowess on your part!

Okay, DT is based on another scanner (which is meant to run at 30K). So what? Just because something is based on something else, doesnt make it a "copy", but a "derivative".

Well actually you have a good point. Maybe a great point. But it's a...

DISTINCTION WITHOUT A DIFFERENCE

When you go to a flea market and see an imitation Louis Vuitton purse from Hong Kong that looks almost identical to the original, with the only differences being that some parts are printed vinyl rather than tanned leather, and instead of the rings being real gold plated nickel over steel, they are rather gold electroplate over base-metal, do you call this a "copy" or a "derivative"? It's probably a matter of dialect... But the fact is, than a genuine Louis Vuitton will literally last a lifetime even for someone like "Indiana Jones" whereas the "derivative" will only last even the most careful wife a summer... If you compare these two purses side-by-side, you might notice that the metal rings are larger on one, or shaped slightly differently, or the shade of brown and beige is a bit different, etc. But from a ten foot difference, you might not tell them apart. But again, is that a "copy" or a "derivative". On talk radio they call that "a distinction without a difference"...

BEARING SIZE AND IMPACT ON MAGNETIC FIELD

Now, specifically when talking about the original Cambridge model 6800 and all "derivatives", the original one used American-sized bearings, having outside diameter of 0.1875 inches (4.76mm) and shaft size of 0.0935 inches (2.38mm) whereas Chinese scanners I have seen including DTs use metric-sized bearings, having outside diameter of 5mm and shaft size of 2mm. In other words, the outside of the bearing is bigger, but shaft is smaller. Does it make a difference? I guarantee anyone from a distance of only a few feet won't be able to tell the difference by looking at them. But the outside diameter defines the area in which you can place the coil. The larger area makes it easier to put a coil that's not quite formed as well. But unfortunately this reduces the flux density -- permeance coefficient goes down from around 1.7 in the case of Cambridge scanners to around 1.5 in the case of "derivatives". This reduces torque constant by perhaps 10% or so.

BEARING SIZE AND IMPACT ON ROTOR STIFFNESS

The really bad news is the shaft size, which goes from 2.38mm to 2mm. Again, doesn't sound like much, but if you want to put a mirror in the slot that is 0.85mm, the 2.38mm shaft gives you around "a mirror's width" of metal on each side, whereas the 2mm shaft gives you much less metal. And finally, since stiffness goes as the fourth power of shaft diameter, a shaft that is 2mm instead of 2.38mm is only (2 / 2.38) ^4 = 0.49 times (around half) as stiff as the 6800. This dramatically affects resonant frequencies (i.e. at what point you start seeing squiggles and wiggles) that I talk about in my 30 minute video, and which I can easily show and everyone can see in DT scanners, especially when tuned to 40K because, as I discuss in my video, the higher you tune something, the more you're going to exacerbate any existing resonances in the system.

CHANGED OR IMPROVED?

Now if there is evidence that the chinese haven't changed and improved the original scanner at all and DT30 is essentially the same, then thats another story and then please link me to some evidence so Ill make better decisions.

Hehe. Oh, there are changes alright, but I'd never call them "improvements"!

CHANGED POSITION SENSOR LED

One thing that they change is the LED in the position sensor, which is actually very special on Cambridge scanners and only made by one company on earth (we use the same LED in our Saturn scanners). This LED has super-special wide angle capability. It's the only LED whose polar field intensity does not vary with angle over nearly 140 degrees. But this LED is also perhaps nearly 1000 times more expensive than ordinary LEDs! The result of using another LED is that linearity is greatly affected. (And on Cambridge 6800s made since 1995 they actually have two LEDs -- one on each side of the vane -- a technique they patented, so nobody else can do this...)

CHANGED COIL

Another change is that Cambridge coils are actually wound pretty well -- nearly the best I've ever seen (with the best being General Scanning, who invented the whole technique and later actually purchased Cambridge). These coils are wound with special machines that wind wire in "3D". Chinese coils are wound by hand, and then further manipulated by hand to get into shape. The result is not as good of field consistency.

CHANGED METHOD OF SECURING THE COIL

And finally and the worst performance-degrading change is that while Cambridge scanners use really good thermally-conductive epoxy to hold the coil into place, almost every Chinese scanner that I have ever seen uses either simple "Araldite" type epoxy, or super glue. DT may use thermally-conductive epoxy -- I just can't remember, but I'd be amazed if it was as good as what Cambridge uses, plus Cambridge puts the epoxy in there using techniques that are generally not available to other companies (not even Pangolin, which is one of the reasons we chose not to make that kind of scanner). The result is that the heat capacity of the scanner is degraded (see my video to understand this).

So sure, there are CHANGES. No doubt about it. The small changes can wind up manifesting themselves in at least small performance degradation. But it's also way less money too!

WHICH ONE WILL MAKE YOUR WIFE HAPPIER?

My Louis Vuitton purse analogy is really a very good analogy. Louis Vuitton will literally last you a lifetime. You'll simply get sick of it and buy another purse before it falls apart. But Louis Vuitton "derivatives"?

With that being said, DT and Sonima make the best scanners that I have ever seen in China. Both of them are a fraction of the cost of American-made Cambridge scanners, and they're definitely good enough for most people. In fact, I have a projector at Pangolin with DT-40 scanners as well (projector given to us as a gift). But if we're talking about differences, buy your wife a Louis Vuitton purse and an imitation and see which one she likes better...

OVER-CLOCKING ANALOGY MIGHT NOT HAVE BEEN SO GOOD...

Overclocking a CPU is risky, but if done right it works. If this point is about scanners like DT40, then I don't see the problem.

Hopefully with some additional blanks filled in above, you start to "see the DIFFERENCE". But is the difference "a problem"? If you're willing to sacrifice projected image quality, linearity and lifetime in exchange for a lower price, then there is no "problem".

Bill

[cipher0]

DISTINCTION WITHOUT A DIFFERENCE

I wasn't talking about "cosmetic" differences, Bill.

A distinction without a difference is a type of logical fallacy where an author or speaker attempts to describe a distinction between two things even though there is, in fact, no actual difference

Not what I'm doing. My point is you can't say something is a clone because it was derived from something else. Now if it is essentially the same, that's another thing. I don't know if it is and I'm not saying it isn't, I want to know myself.

And about your Louis Vuitton example... it is very often the case, but often it isn't. Often the "real brand" products are not different in terms of quality to the some "chinese clones". The reason they are expensive is because the have an official respected brand name attached to them, that is all. Ironically some brand products today are made in the same country by same class workers
Not that there is anything wrong with that.

buy your wife a Louis Vuitton purse and an imitation and see which one she likes better...

Hehe, some of them are so good most people can't tell the difference actually.

If you're willing to sacrifice projected image quality, linearity and lifetime in exchange for a lower price, then there is no "problem".

Now that's another thing. In your previous analogy you mentioned "reliability, or at least convenience" as "problem".
This might be a problem, but only depending on *how much* "sacrifice".

You've given reasons why the chinese DT scanners won't give the same quality results and while I don't understand the physics behind it, I accept them.
However, from positive reviews from users of those scanners, I'm not sure if the differences between the chinese and your future and Eyemagic scanners are noticeable for most people and have enough impact on quality to choose those over DT.

I think a side-by-side comparison would answer all this. I haven't found the tests and their results you guys have done before.

Thanks Bill.

[Galvonaut]

Thanks Bill. I've just checked the CTs and they are 2007 models, although look a lot newer. On inspection I noticed that the Y galvo has been installed with the mirror the wrong way, so the FS mirror pointing up - better change that.

The amp that came with them is the 1M0 amp which I know very little about.

I still don't really understand the vector/point thing. Is it a case of the interpolation of an SVG into being point based is made after the designing, scaling and geometric correction, making it more efficient in optimisation? This probably needs a new thread

Keith

[Pangolin]

Do DT scanners give results whose quality is acceptable to most people? Sure. At least in the absence of a better-educated and more-discerning public.

Let me give you an example. When I came to my very first Photon Lexicon event, there were a handful of people who were using MediaLas software along with an EasyLase DAC. When I went to this event, everyone was pretty happy with their DAC. At least that was my impression. But when I pointed out to them that -- when projecting the ILDA test pattern, the circle inside the square was twitching, and then cranked up an oscilloscope and showed everybody why it was twitching (sample jitter, and pretty bad sample jitter at that), then this became unacceptable to everyone. At the next Photon Lexicon event I went to, not even a single person was using the EasyLase... The people remained the same. It's just that they became better educated that a) quality could be better, and b) what to look for. (Probably c, d and e as well, and if Buffo comes back into this thread, I am sure he will say more).

For hobbyist who are thrilled at the prospect of producing graphic shows at an affordable price, and who have never seen anything better nor had flaws pointed out to them, DT and the myriad of other scanners on the market may be acceptable to them. But it could very well be that once I point out to them what to look for, where to look, and why the flaws represent a lack of quality, then it could very well be that the more educated public will also become more demanding, just as what happened with the EasyLase DAC situation...

Regarding Louis Vuitton, what I wrote was absolutely true. These bags will last a lifetime. Imitations won't, period. It's not all about brand awareness. It costs money to produce goods from the top-quality leather, fabric and metal materials. Now, in a similar way as can be demonstrated with the hobbyists who have never had a laser before, for people who have never had a real Louis Vuitton handbag, they are thrilled to have something that looks and seems similar. But if anyone has ever had both, there will be no question as to which one they prefer.

Keith, regarding my point about vector is this. See, if you put more points along a line, either with a point-oriented editor, or by "interpolating" additional points on that line using a higher point density, what happens is that the "slew rate" becomes slower. Effectively, distance between steps becomes shorter. Since distance and slew rate become more relaxed, it puts you further away from the large signal domain. The cost is scan speed. Placing additional points on the laser media test pattern -- whether manually using a point editor or automatically using a computer will slow the scanning down.

Bill

[Galvonaut]

It's like third wave coffee - oh boy you can tell the difference! I'm a newb in the laser world but I can see quality difference - maybe not understanding it yet but certainly seeing it.

Education is really important, and going to LEMs to see the different builds, components and methods used. I've not started my build yet but I'm aiming for the best I can afford - not in power but quality, using single mode diodes, at least reasonable galvos and other components.

Reduction in slew rate makes complete sense Bill. Can interpolated points be tuned to specific scanner responses - optimised for the scanner itself, so additional points aren't added where or when slew rate increase would cause image problems - or do the scanners not function in this way?
I imagine (with my very basic knowledge of scanning) that knowing the precise scanner response, although processor hungry, would enable points to be added in places that only require them and only when the addition would not increase slew. Maybe I said that twice in 2 slightly different ways :P

Keith

[cipher0]

Let me give you an example. When I came to my very first Photon Lexicon event, there were a handful of people who were using MediaLas software along with an EasyLase DAC. When I went to this event, everyone was pretty happy with their DAC. At least that was my impression. But when I pointed out to them that -- when projecting the ILDA test pattern, the circle inside the square was twitching, and then cranked up an oscilloscope and showed everybody why it was twitching (sample jitter, and pretty bad sample jitter at that), then this became unacceptable to everyone. At the next Photon Lexicon event I went to, not even a single person was using the EasyLase... The people remained the same. It's just that they became better educated that a) quality could be better, and b) what to look for. (Probably c, d and e as well, and if Buffo comes back into this thread, I am sure he will say more).

Very well. Then educate us please. Show us a comparison. That's what I have asked already. If you have shown results already, has it been recorded for others to see?
In your example the quality difference in real (not just test) animations might indeed have been noticeable for most people and enough reason to change to another product. But will it in this case? Maybe you think it will, but I'm sorry to say your opinion isn't enough for me. Don't take this as rudeness, that is not my intention. What I think is something you make might seem better to you than it really is, or what you think of noticeable quality difference might not be for some of us, or some other reason.

Regarding Louis Vuitton, what I wrote was absolutely true. These bags will last a lifetime. Imitations won't, period.

How can you make such a claim? Me and my friends have seen and used copies of branded products, which we also had by the way. We couldn't and still can't tell the difference, so I can make this claim. But you can't make that claim unless you've seen all the "imitations" of every Louis Vuitton product which you just physically can't. All you can say is you haven't seen a good quality ripoff, but that's different.

It's not all about brand awareness. It costs money to produce goods from the top-quality leather, fabric and metal materials.

But are they always using the most top-quality material? No, they do not. And then they rely on their brand name. Is it always the case? No. But it is also not always the case that a brand product is expensiver because it uses better quality raw materials.

Now, in a similar way as can be demonstrated with the hobbyists who have never had a laser before, for people who have never had a real Louis Vuitton handbag, they are thrilled to have something that looks and seems similar. But if anyone has ever had both, there will be no question as to which one they prefer.

Same as above.

Again, I'd love to see some comparisons.

[White-Light]

Now, in a similar way as can be demonstrated with the hobbyists who have never had a laser before, for people who have never had a real Louis Vuitton handbag, they are thrilled to have something that looks and seems similar. But if anyone has ever had both, there will be no question as to which one they prefer.

Ciphero, I'll give you a real world example if it helps.

Quite a long time ago I went to another members house and saw their projector with DT 40's. Very impressed I was.

A short while after that, the person concerned changed those scanners to Cambridge and by coincidence (nothing more) we had another laser viewing evening. The difference was amazing.

If you'd never seen the same projector with the different scanners, you'd have never have guessed there was actually any difference. However, with the Cambridge fitted the colours looked cleaner (clearer more pure colours), the discreet colouration in multi-coloured fans had much sharper delineations between the different colour bands and overall the pattern simply looked sharper, cleaner and a whole lot "better".

The conclusion in this is simple, even from a simple beam show (not something you necessarily would associate with a need for perfect scanning which is more usually associated with graphics), the difference in the quality of the scan was plain to see.

So the moral of the story here in layman's terms, is you usually get what you pay for.

As for this thread and what to buy, one of the reasons why a lot of people are excited about Pangolin's new 506 scanners, is because early indications from independent testers seem to be hinting towards a Cambridge quality of performance but ostensibly at a much more budget orientated price. If this pans out in independent tests (and I really have no reason to doubt that it wouldn't - just staying neutral here), then they could represent a new level of performance for a very budget price.

Ultimately in terms of what to buy, if you can wait a little longer, I'd await the tests results and pricing of the 506's before making a decision. If you absolutely can't wait, then certainly DT or EMS are probably two of the better choices out there for below Cambridge pricing at the current time. Early indications are, the 506's might just change that though. I certainly know where my budget would be going, and that's in the bank for a few more weeks!

[swamidog]

the difference between DT (dragon tiger) and CT (cambridge technologies) scanners is pretty astounding.

for years i've used DT40w's in my projector and i've had really good success with them. however, there is oscillation/ringing that is visible in some straight and diagonal lines. will the average viewing notice these? most likely not, but after working with CT galvos for a while, it's kind of painful to watch content through my DT's.

if the pangolin scanners work as advertised, i will be very happy to assign my DT's a nice dusty location in my junk bin. i'm waiting for mixedgas' review. he has forgotten more about scanners than i will ever know. if they check out, and i have no reason to expect they won't, i'll be on the phone to bill..

Very well. Then educate us please. Show us a comparison. That's what I have asked already. If you have shown results already, has it been recorded for others to see?
In your example the quality difference in real (not just test) animations might indeed have been noticeable for most people and enough reason to change to another product. But will it in this case? Maybe you think it will, but I'm sorry to say your opinion isn't enough for me. Don't take this as rudeness, that is not my intention. What I think is something you make might seem better to you than it really is, or what you think of noticeable quality difference might not be for some of us, or some other reason.


How can you make such a claim? Me and my friends have seen and used copies of branded products, which we also had by the way. We couldn't and still can't tell the difference, so I can make this claim. But you can't make that claim unless you've seen all the "imitations" of every Louis Vuitton product which you just physically can't. All you can say is you haven't seen a good quality ripoff, but that's different.


But are they always using the most top-quality material? No, they do not. And then they rely on their brand name. Is it always the case? No. But it is also not always the case that a brand product is expensiver because it uses better quality raw materials.


Same as above.

Again, I'd love to see some comparisons.

[Pangolin]

How can you make such a claim?

Because my wife has had lots of such bags, purchased from places all over the world, including directly in companies in Hong Kong. I know of which I speak... For the genuine bags I bought her, she still has them... They look like new...

I wouldn't want to lose 10k because of slight graphic correctness.

Hehe. You're already unwittingly giving up a lot, by tuning 30K scanners to 40K. Remember my discussion of small signal domain and such...

OK I'll put together a video showing the DT40s and the limitations imposed by tuning 30K scanners to 40K, and then various things with our own scanners.

Bill