Home Theater Forum and Systems banner

1 - 2 of 2 Posts

·
Registered
Joined
·
71 Posts
Discussion Starter #1
Hi guys. I'm facing this 'issue' of sort which I wanted to discuss. I'm trying to decide where to place my JVC RS-46 in my HT room, and have to pick from one of two potential locations. I placed the projector in both locations yesterday (using cardboard boxes to hoist the projector up) to see how to picture looks. It seems that pictures generated from the FURTHER of the two locations is brighter in majority of the cases, whereas it should have been the other way around .. :confused:


Here's how I did the test:

>> Using a DSLR, I took pictures of the exact same video frame from both locations
>> I used a tripod to ensure DSLR doesn't move
>> DSLR's autofocus was disabled
>> Saved pictures in NEF format to get RAW untouched pictures for making comparisons in Photoshop
>> 14 scenes were captured from both locations
>> The first of the 14 uses 'Natural' setting defined in RS-46 (PS3 XMB Screen), while the remaining 13 (Avengers 3D Blu-ray) used the default '3D' setting
>> Screen used is a 119" 16:9 Da-Lite HD Progressive 1.3 Gain screen
>> Tripod was about 6 ~ 7 away from the screen, in the center of the room

Everything shown in both drawings below is to scale.

Position A (Throw distance: 15.5 feet):



Position B (Throw distance: 12.5 feet):



Open Spoiler to see comparison GIFs:

Spoiler


1/14: Position B's picture is brighter



2/14: Position A's picture is brighter



3/14: Position B's picture is brighter



4/14: Position A's picture is brighter



5/14: Position A's picture is brighter



6/14: Position A's picture is brighter



7/14: Position A's picture is brighter



8/14: Position A's picture is brighter



9/14: Position A's picture is brighter



10/14: Position B's picture is brighter



11/14: Draw



12/14: Position A's picture is brighter



13/14: Position B's picture is brighter



14/14: Position A's picture is brighter






Results:

>> In 9 pictures, I found Position A pictures to be brighter (to varying extents)
>> In 4 pictures, Position B's pictures were brighter (to varying extents)
>> In 1 picture, both were equally bright
>> In some pictures, Position A's result also looked better, e.g. more accurate skin tones, color, etc.

Questions:

>> Can someone explain this anomaly to me ?
>> Maybe there's some variable I may have overlooked possibly ?
>> Or should I trust these results and put the projector at the further of the two distances ?
 

·
Registered
Joined
·
7 Posts
This has to do with the lens system on your projector. According to JVC you projector has an f stop of 3.2-4. This right here tells you that you will have varying light over the range of the projector depending on where you position it. However, the throw ratio is 1.4-2.8, at 12.5 ft your throw ratio is 1.44 whereas at 15.5 ft your throw ratio is 1.77. So, you should have a brighter image on the closer one. There must be something else going on here but maybe this will get you pointed in the right direction.
 
1 - 2 of 2 Posts
Top