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grogthegreat
Joined: 16 May 2007
Posts: 166
Location: San Diego, CA
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| Posted: Thu Apr 23, 2009 5:10 pm Post subject: |
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| tommo2 wrote: | | Elaine Benes wrote: | | You're going ES to EM, the difference in resolving power will be very significant. Actual, physical tube size between so called "8" tubes and so called "7" tubes is so tiny as to be meaningless, the actual difference in the image size is mere mm's. |
Correct me if I'm wrong, but isn't the picture quality directly proportional to the phosphor area used.
So brightness (lumens)/resolution etc will actually increase quite a lot between 7" and 8"?
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From my understanding the resolution that a projector is capable of is the tube size divided by the beam size. So to increase your resolution capabilities you could increase the size of the tube (7" to 8" for example) or you could focus the electron beam better in order to reduce its size on the tuber face. EM machines go for the second route and the difference is huge. I'd rather an 8" EM machine than a 9" ES machine. Bigger tubes do make a difference, especially in terms of brightness and tube life, but not as much of a difference as going from ES to EM.
Hope this helps,
-Greg
_________________
First projector: Sony 1252q with 3500 hours
Second projector: NEC 9PG+
current projector: Sony G90
100" 3:4 draper screen.
I must keep upgrading till the voices stop!!
"I CAN HAZ CRT PRUJEKTER."
-Curt Palme
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Elaine Benes
Joined: 25 Apr 2006
Posts: 1416
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| Posted: Thu Apr 23, 2009 7:38 pm Post subject: |
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| tommo2 wrote: | | Elaine Benes wrote: | | You're going ES to EM, the difference in resolving power will be very significant. Actual, physical tube size between so called "8" tubes and so called "7" tubes is so tiny as to be meaningless, the actual difference in the image size is mere mm's. |
Correct me if I'm wrong, but isn't the picture quality directly proportional to the phosphor area used.
So brightness (lumens)/resolution etc will actually increase quite a lot between 7" and 8"?
No 7" crt tube will display an image on the complete tube face, it is always at least half an inch from the tube edge, maybe even 1 inch away.
Example: A 7" crt tube may only display an image on the tube face of 5" x 5" = 25 square inch of phosphor used (image 1 inch from tube edge).
A 8" crt tube may only display an image on tube face of 6" x 6" = 36 square inches (still 1 inch from tube edge)
So that would be nearly a 50% increase in brightness/resolution, right? |
Nope.
Firstly, when you compare the actual physical size of the tubes in question, the difference is mere mm, not inches, as in your assumptions. "7" and "8" are only nominal sizes and don't have any real reference to the usable phosphor of the tube. I've measured the difference between Marquee "8" tubes and NEC "7" tubes, and I believe the Marquee's are actually 5mm larger in width, so less than a 1/4" actual size difference...
Also, how the tube is driven has as much or more to do with light output as physical size. 1292's are nine inch tubes, yet they are MUCH less bright than an NEC XG, which is a seven inch tube. The actual glass envelope of the XG tubes is EXACTLY the same size as the PG tubes too, btw, so when XG's are referred to as "8" projectors and PG's as "7" projectors, that tells you the "sizing" is only nominal...
Resolving capability is *somewhat* tied to physical size, in that, it is EASIER to resolve a higher resolution if you have a greater area to do it in, BUT, again, the projectors electronics have a greater impact than just the physical size of the tube.
Look at a 9" ES focus machine and try to tell me it is "sharper" than any NEC PG, it simply isn't....
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Thu Apr 23, 2009 9:16 pm Post subject: |
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There are no such things at 7" or 8" tubes. It's all a load of marketing crap.
They all have a diagonal size of about 160mm. And a 9"er is actually 190mm. The D50 does have some piddly little tubes, but that's not the pj in question here.
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