| zzonbi |
What is the FOV (field of view) of the Lumen Lab 320mm focal length lens, costing 29$? What is the aperture limited (light circle) one and the good image one, so it can still separate .264mm on a say 5X magnification projection?
Also do you know the exact aperture value, ie related to back focal length, not the approximate f/4, from 320/80.
TIA
Simply put, does it cover decently 17'' panels, or merely 15'' at 5-6X?
I understood this and the pro 450mm LL objective are about the only options, except more expensive photographic lenses, or undocumented surplus copy lenses. |
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| Rox |
I donīt know the lumenlab's standar triplet's STATED FOV. But the F number is somewhere F=5. (320 mm focal & 62mm aperture?)
The other one (coming soon) is the 500mm focal and 100mm aperture triplet. F=5 again.
There are more factors than FOV as well to determine the max circle (LCD size) such as throw. The FOV is a setip tependent circle but the FOV angle is constant. Personally I prefer to use the FOV angle, rather than FOV circle in milimeters. |
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| zzonbi |
Ooops, I was hoping for a better F/D given the 80mm value. Even old dia projector objectives have 1:2.8 and 60degrees angles, with huge resolutions. But they're too small for my coverage needs.
Yes, I prefer the FOV angle too, but any would do since we can convert between them. The angle isn't precisely constant too, as it may vary with the object distance.
I don't need to cover more than 17'', regardless of angle or focal length. So I need 2*arctg(17/F) angle with as good F/D as possible, but only modest resolution vs photographic applications. |
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| zzonbi |
| correction 2*arctg((17/2)/F) |
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| superdaveumo |
| Yeah, the FOV angle and the FOV circle are directly related. You can't have one without the other. The 80mm has been said to not perform well with a 17" LCD. Even the 135mm has fuzzy corners. The new 500mm Pro lens from LL is supposed to resolve these issues with 17" LCDs. It also costs $200 and isn't available until after January. But, if it proves to work flawlessly with a 17" LCD, it would be your best choice (without considering price). If price is an issue, you'll have to try your luck on e-bay for an opaque projector lens or a copy lens for a large format camera. I've heard that 22" FL (559mm) opaque projection lenses can handle 17" LCDs. |
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| zzonbi |
'The 80mm has been said to not perform well with a 17" LCD.'
Then perhaps it still covers all corners, meaning the image isn't cut, despite unclarity. That would be good to hear, because 200$ is pretty steep for a project now, with commercial prices falling and LED projectors around the corner (they're announced in January 2006).
But I can part much easier with 29$ for the sake of experimenting and DIY ;) |
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| Rox |
| the 17" not working is relative, it all depends on the trhow. |
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| zzonbi |
| Oh OK, so I'm back to the beginning (well, almost)... |
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