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Discussion Starter · #1 ·
I have a DLA-HX2 setup with a 110" Dazian CCC screen (16:9).


I calibrated with HCFR and read 5.5 ftl at 100% IRE window.

I believe this corresponds to approx 5.5X36 (36 sq ft screen) or 200 Lumens.

I always thought this was low and my measurement or calculation was wrong.


I had the "bright" idea of trying to use my digital camera as a light meter by taking a manual spot exposure and converting EV to LV to LUX or FC using standard tables and charts. Last night I took the spot measurements at various positions and zooms which all corresponded to about [email protected]=5.5 (5 to 6). This corresponds to 10.51fc or 374 lumens which seems more reasonable than the HCFR measurement.


What gives? Are my calcs wrong? Is such range of errors reasonable?


I should note that setting contrast with HCFR using the brightness measurement never seemed to work properly, but that could be my projector gamma off. Thus, I suspect HCFR.


Thoughts?


db
 

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Discussion Starter · #2 ·
Forgot to mention - at these relatively low illuminations (for a camera), there is only a 1/2-2/3 EV difference between the Eye-one HCFR reading and the digicam. Could easily be this much error in the digicam.


I will try another digicam tonight and see what result.


db
 

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Discussion Starter · #3 ·
On night one, I used my G10 to yield an approx LV of 5.5=10FC.

On night two, my Nikon D70 reads LV=6 or approx 15FC; HOWEVER, the D70 is well known to underexpose by 1/3-2/3 stop, so we are back to about EV=5.5.


This would put the projector output at 374 Lumens (rated at 500, 374 is with 50% aged bulb and calibrated).


Thus, am sure Eye One is used for relative Y measurement and color calibration, not absolute measurements.


Ordered a CA-813 today.


db
 
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