Originally Posted by blake
I moved this message from the Lumagen forum as its more applicable to JVC RS4500 in general.
I have this projector arriving in about a month for a dedicated HT under construction. It will be in a fully ventilated hush box so I can run it on high laser. None the less, I have repeated my brightness estimates and perhaps I overestimated it.
In an ideal world, I would add a Panamorph DCR lens AND Lumagen Radiance Pro right off the bat (like some of the owners here) but:
1) I can only budget for 1 of these 2 now
2) DCR lens throw ratio is 1.40, which puts me at 196" min throw (1.40 x 140" wide scope screen). Furthest back I can get the projector is 198". Yes this COULD technically work, but JVC quotes +/- 10% error for throw estimates in the user manual, so there is a good chance I couldn't get it back enough depending on my particular unit.
I thought I would have more than enough light output for good HDR (with dynamic tone mapping - Kris Deering frequently reminds us we don't need super high lumens for HDR if good tone mapping used, like a Lumagen Radiance Pro). However, I now question this.
Did I do these calculations correct?
JVC RS-4500 running HIGH LASER mode
Throw distance= 198" (16'6"). Can't move PJ any further back than this.
Screen gain = 0.8 (SSE Enlightor Neo, unbenchmarked)
Screen size = 2.40 AR, 140" width x 58.3" height (152" diagonal)
High laser = 3000 lumens
Calibrated (no color filter) is ~2500 lumens
0.8 gain = down to 2000 lumens
Jack Liu projector calc gives only 21 ftL.
This is lower than Projector Central (but this one didn't allow lumen output per se to be specified).
But if I do by hand: 2000 lumens / 56.4 sq ft = 35.5 fL -- but perhaps this doesn't factor is projector ZOOM?
A) Which is the correct value?
B) How much would clamping down the manual iris (to improve contrast) cut down brightness? Ex. -4 or -7
C) Is this brightness "adequate" for HDR content?
If you are zooming and not using an A-lens then you figure the screen size width but with an aspect of 16:9, matching the projector panel.
So with a 140” wide screen (scope or 16:9) doesn’t matter with the zoom method. With a .8 gain and 2500 lumens gives you 26fL to fill the entire 140” screen width. You would have the same 26fL if you had a 140” wide screen that was 16:9 aspect ratio as well.
You really won’t be able to clamp down on the iris at all.
Even with the Lumagen DTM, personally I consider 30fL the bare minimum for HDR content. Sure DTM can make HDR content watchable at standard SDR brightness level, but then you are basically just watching an SDR image.
Personally I think you are asking to much out of the RS4500 without the use of the DCR lens or a higher gain screen. If you added a DCR lens you would have around 36fL.
If you didn’t use the DCR lens, but used an 1.3 gain screen like a Stewart or Screen Innovations micro-perf, you would have around 40fL.
If you used the DCR lens with a 1.3 gain screen you would have around 55fL.
The use of either a positive gain screen, the DCR lens, or both will give you way better HDR experience and will also give you a better SDR image because you will be able to clamp down on the manual iris.
But the Lumagen is a necessity first and foremost.
So my priority would be Projector, Lumagen, (possible different screen with a higher gain, if you haven’t already bought the Enlightor Neo), then the DCR lens.
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