# JVC RS-46 :: Smaller throw distance results in darker picture ?



## ahmadka (Nov 27, 2010)

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 .. 


*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 ?


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## epwhitney1 (Dec 30, 2014)

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.


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