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*To*: telecine at alegria.com*Subject*: The world of CRT*From*: orton at popstudios.com (Mike the Brit [Michael Orton])*Date*: Thu, 29 Oct 1998 16:54:39 -0800*Cc*: orton at earthlink.net*Resent-Date*: Thu, 29 Oct 1998 18:56:29 -0600*Resent-From*: telecine at alegria.com*Resent-Message-ID*: <"HagOfD.A.sUE.-5QO2" at sun>*Resent-Sender*: SmartList account <slist at alegria.com>*Resent-To*: multiple recipients of <telecine at alegria.com>

Ladies & Gentlemen of the TIG: I've read the paper submitted by Jerry Rodgers, and I have come to the conclusion that there are several difficulties with this document. One of the opening statements is that the best image scanning source available could be determined by mathematics and physics. Agreed, so I was looking forward to both of these techniques being applied to the problem. 1. The equation for "space charge current". Why is this introduced, and then just as quickly dropped? I have to say that I had no idea that this could be written as 14.6x10E-6.(L/ra).(Eb/b^2)^3/2. Having said that, I don't care! What's more, neither does the author! Apart from a fleeting mention that "active tube length is an interesting parameter", the result of this statement is not used anywhere else in the document. 2. We have some sophomore maths/physics to show that the deflection ANGLE is proportional to the applied transverse magnetic field and inversely proportional to the sq.root of accelerating voltage. Again, so what? This information does not really figure in the following non-rigorous treatment of resolution. The elementary conclusion gained from all this math is that the smaller the deflection angle, all else being equal, the better the H and V linearity. I should have thought this qualitative conclusion could be derived from one simple drawing. 3. The above conclusion is used to demonstrate the intuitively obvious: that the spot size will grow as a result of a non perpendicular beam landing. Absolutely true! why did we need irrelevant equations for this: again, a simple drawing would have sufficed. This is where the maths starts becoming a bit suspect. See #4. 4. The author states that theta for an active tube length of 254mm (where did this figure come from?) and a deflection of 83.8mm is equal to sin(83.8/254) = 19.27degrees. Not in my math class! The correct answer is ARCTAN (83.8/254) which is about 18 degrees. This equates to growing the spot by ((1/cos(arctan(83.8/254)))-1)*100 percent or ABOUT 5.3 PERCENT. 5. Even leaving the gross mathematical errors aside, I cannot agree with the apparently arbitrary values to active tube length and deflection. My experience with Cintel tubes is that active tube length is roughly of the order of 16" or 400mm. The patch is about 4" square, giving a deflection of about 2" or 50mm. Now lets do the (correct) math again: Spot percentage increase = ((1/cos(arctan(50/400)))-1)*100 or about 0.78 percent. I believe this figure represents the real world far more: around a 1% or so fall-off in resolution at the picture edge. 6. Real world viewing of the Cintel C-Reality tends to support the math: Has anyone tried looking at the PICTURES? I have. A group of us from POP had the chance to go to Valencia to "C the Reality" last Monday. The pictures I saw on the Hi-Def machine were clean, resolute and seemed to be free of artifacts. Unfortunately, the machine kept crashing on me (sigh). I anticipate that, given the software cleanup required, Cintel will have a very worthy competitor to the Spirit, (which I also like a geat deal), around NAB time if not sooner, notwithstanding any half-assed mathematical "evidence" to the contrary. 7. Xenon is spelled with an "X" Finally, may I say it is customary for "scientific" papers about to be published to be subject to peer review. This avoids any errors in such documents being pomulgated, and may help prevent embarrasment to their authors. It also stops people like me taking the piss. The paper here presented cries out for review. I'd like to recommend that about a half-dozon TIGrs be available for a peer review process, nominated by people on the TIG. I'll start off by nominating Dave Corbitt and Martin Euridjian for this job. TTFN Mike (mine's a pint) Orton --- Thanks to Howard Lukk for support in 1998. No product marketing allowed on the main TIG. Contact rob at alegria.com 1014 subscribers in 38 countries on Thu Oct 29 18:55:21 CST 1998 subscribe/unsubscribe with that Subject: to telecine-request at alegria.com complete information on the TIG website http://www.alegria.com/tig3/

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