| N_Cook <diverse@tcp.co.uk>: Jun 19 10:50AM +0100 On 18/06/2018 15:07, Phil Hobbs wrote: > adding, but the net effect will probably be significantly worse.) > Cheers > Phil Hobbs I'll have another go of setting out, with retort clamps and a mesh as a focussing tool and measurement tool , to get some measurements.. I'd not considered luminance loss, as long as its not more than the gain from keeping a projector as-is and simply reducing the diagonal , increases the luminance in terms of per square inch of the projected image. |
| Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Jun 19 11:14AM -0400 On 06/19/2018 05:50 AM, N_Cook wrote: > I'd not considered luminance loss, as long as its not more than the gain > from keeping a projector as-is and simply reducing the diagonal , > increases the luminance in terms of per square inch of the projected image. Wouldn't it be nice. Unfortunately the loss applies to every point in the image--the reduced field of view is another issue. Consider a single LCD pixel. Light from that pixel expands to fill most of the projection lens (generally not all of it, because otherwise the dimming at the edges of the picture would be worse than it is). Moving the lens further away reduces the angular area (solid angle) quadratically, which dims that one pixel quadratically as well. You'd be better off with a single large, long-focus achromatic positive lens. For example: <https://www.ebay.com/itm/82-mm-dia-x-320-fl-Achromatic-Doublet-Lens-Rolyn-Optics-computer-optimized-ac/132657998078?hash=item1ee30868fe:g:Jr8AAOSwrptbHWLE> Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com |
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