[SOLVED] best projector distance

[robert600]

I have a new for me projector coming (Viewsonic PX727-4k) and I'm getting the room ready for the change. It's throw ratio is 1.5 to 1.8. The width of my screen is 120" so it seems the projector distance from the screen to the lens can be between 180" and 216". It'll be a ceiling mount and I have a joist at 184" and another at 200".

Any thoughts about which of these joists to use? Would the one at 184" result in a noticeably brighter picture (I'd like to use eco mode if possible to prolong the bulb life) and, if so, is there any negative to using it as opposed to the one at 200"?

I guess I'm not sure if there's a 'sweet spot" in these throw ratios or if the resulting picture is the same throughout the entire zoom range?

 

[Wolfshadw]

Is 120" your screen WIDTH or screen Diagonal?

@120" Screen Width (137: Diagonal), you've got an optimal throw distance of 196"
@120" Screen Diagonal, you've got an optimal throw distance of 188"

In all honesty, it's not going to matter which joist you use as they're close enough to your optimals as to be well within adjustment ranges.

Use the Projection Calculator found at Projector Central.

-Wolf sends

 

[robert600]

120" screen width.

So ... no appreciable difference in brightness between the 2?

I'll check out that calculator thanks.

 

[USAFRet]

184" vs 200".
16"

Less than the difference between leaning forward in your seat, or relaxed reclining.
Either one would be good, depending on how you are sitting at that particular moment.

 

[robert600]

That calculator is quite nifty! It seems the difference in brightness between the 2 distances is only 1 or 2 nits ... depending on if I use projector central's estimated brightness or the manufacturer's specs.

Interesting that projector central's estimate of brightness is a bit less than 1/2 of the manufacturer's spec. The manufacturers tend to be so optimistic when it comes to brightness!

 

[robert600]

184" vs 200".
16"

Less than the difference between leaning forward in your seat, or relaxed reclining.
Either one would be good, depending on how you are sitting at that particular moment.

I'm not sure how the viewing distance from the screen affects anything? Unless I had the projector mounted to my hat lol. Or does greater viewing distance also decrease brightness?

 

[Wolfshadw]

You also need to take into account ambient lighting. If you can darken the room fairly well, then brightness isn't going to be too much of an issue. If there's going to be a lot of ambient light, then the throw distance is going to start becoming a factor. But again, we're also talking about less than two feet. It's not going to make THAT much of a difference.

In my old set up, I had black-out curtains covering my West-facing bay windows and didn't have any problems watching Sunday football on a 135" diagonal, 19' throw distance with my Optoma HD20 projector.

-Wolf sends

 

[robert600]

Ambient light won't be an issue.

"@120" Screen Width (137: Diagonal)"

I've never quite understood reports of "diagonal" because of the different aspect ratios that different media uses ... the only thing that remains constant is the width; the amount of screen height (and therefore the diagonal) that the image uses changes with the ratio. Without knowing the aspect ratio of the image ... the diagonal is kinda imprecise. So, for instance, if my math is right, for a 120" width screen:

4:3 AR = 150 dia
16:9 AR = 137.7 dia
1.85:1 AR = 136.4 dia
2.35:1 AR = 130.4 dia


In any event, I guess I'll go with the joist that is 200" away from the screen. I may at some point add 'wings' to my screen (I have 7" on each side of the screen that I could use). Having the projector back that extra distance would allow me expand the picture to that new size. The other advantage I can think of it is that the projector will be a little further behind the seating position so a little quieter.

Turns out the lens on that projector is not on the center line of the projector casing so I guess I'll have to offset a bit from the center line of the screen for the ceiling mount. I guess I pretty much have to have the projector here to figure that distance out (appears to be about 3") but at least I can go ahead and mark out the screen center line etc on the joist. Also, I think there's a ceiling light fixture that will need to be moved.

Thanks for all the help, if I can figure out how - I'll mark best answer.

 

[Wolfshadw]

The aspect ratio is going to depend on the resolution the projector is outputting. If you have it set for 1920x1080, your aspect ratio is 16:9, hence the 137.7" diagonal. That is going to be regardless of the actual image ratio. A film, shot with a 2.35:1 aspect ratio is still going to be displayed at a 1920x1080 resolution. You'll just have black bars on the top and bottom of the viewable image.

Most higher-end projectors will have a keystone adjustment to off set a minor misalignment from center. So even if the lens is 3" off center, you should still be able to use the keystone offset for that adjustment.

For a best answer, click on the Trophy to the left of the avatar of the person who you deem provided the best answer.

-Wolf sends