Room Obstructions and Lens Shift Question

basspig

basspig

Full Audioholic
After nine years of owning my InFocus IN82, although it's still running well on the original lamp, I'm shooting in 4K DCI 17:9 format and really need to upgrade my projector to 4K to properly show my work to clients.

My studio has a support column near my current projector location. But since the IN82's lens is offset, it's no problem, other than the fact that I must position that PJ close enough to the column that the column doesn't shadow the right edge of the picture.

The Sony VPL-VW675ES 4K projector that I'm contemplating as the replacement has it's lens in the center of the chassis. Also, wanting to get a larger image on screen than I can with the current 13' distance from lens to screen, I had the thought that my new mounting system could be more offset and further back, allowing me to fill the 154" 2.35:1 screen, since the Sony has Lens Shift.

So if I mount the new projector 24" off center axis of the screen, 14' back from the screen (to clear the column) would lens shift handle this properly and without visible image degradation? Specifically the lens on the Sony VPL-VW675ES 4K projector?
 
BMXTRIX

BMXTRIX

Audioholic Warlord
Use this calculator...

http://www.reviewtranslations.com/projection_calculator_en.html

With a 154" diagonal, you have 143" of width and 60" of height in the 2.35 aspect ratio.

Without a anamorphic lens you need 16'3" to 32' of distance to achieve your screen size.

With an anamorphic lens, you can do it from about 13'. So, you will need an anamorphic lens and should do all your calculations based upon a 60" screen height in the 16:9 aspect ratio (123" diagonal).

You then have up to about 32" of left/right lens shift available if the lens is center mounted to the screen vertically. As you raise the projector up, you will lose your left/right lens shift range.

It should work fine, but you must use an anamorphic lens if you are going to the 2.35 aspect ratio.
 
basspig

basspig

Full Audioholic
Understood about the anamorphic lens. Mostly, my content will be 17:9 material, off a hard drive.

Can you elaborate on this lens shift limitation? Sony makes no mention of it. The projector will be ceiling mounted like my existing one, but I wanted to place it further back about a foot and to do that and still clear the column, I need to position it off center about a foot. The column itself is 12'7" from the screen.

The existing projector has no lens shift capability. It seems to be designed to be ceiling or table mounted, as the offset is fixed.

With the Sony, I have to use lens shift to dial in these values.

Why would using horizontal shift limit the vertical? Can you point me to a technical document that explains that?
 
BMXTRIX

BMXTRIX

Audioholic Warlord
Why would using horizontal shift limit the vertical? Can you point me to a technical document that explains that?
Lens shift is possible because the light from the projector doesn't use the entirety of the lens itself. On 'center' the image passes through the center part of the lens.

As you shift the image, the lens elements are moved and you pass the light from the projector through the top, bottom, left, or right part of the lens.

So, why does one lens shift impact the range of the other?

Because the lens is round!

As you move up (or down) from the center of the lens, you get less left/right movement available, because there is not lens to move the image to.

Likewise, if you move left/right from center, you get less up/down movement available because there just isn't any lens there.

It's a really good question that makes sense when you think about the optics being round, but I'm not sure I've seen any videos showing what happens to the lens itself when lens shift is employed. That's something that would be ideal to have for what you are asking about.

You always see the results on the wall in videos, but never what is going on at the lens, on the technical side of it.

That said...

Use the calculator I provided above and you can really map out EXACTLY how your room will work with the projector you selected. It's the best projection calculator on the face of the earth.
 
BMXTRIX

BMXTRIX

Audioholic Warlord
Here's a pic of a NEC with lens shift near the extreme. You can see that the image is passing through the top center part of the lens. This means it can't shift left/right at all.
 
basspig

basspig

Full Audioholic
In giving this some thought, "DUH!" I should have realized that a square image passing through a round lens would have limitations at the diagonals.

I've got to get busy with doing a CAD diagram of my ceiling and screen, with the support column distances all measured precisely. Then I can figure out the optimal position for the projector. I want to minimize the distance from the main carrying beam without impingement from the column. I figure 1 foot offset from center of screen horizontal and 2.2 feet offset vertical.

I think I'll do away with the sliding mount that I'm currently using in favor of a fixed support shelf. I may just make ridges in the shelf long enough to allow the feet to slide back and forth for fine tuning the distance. Also the ridges will reduce the chances of the projector vibrating off the shelf during heavy bass.
 
basspig

basspig

Full Audioholic
The VW 675-ES is here. I've figured out all the lens shift stuff. That works a treat.

Spent some time aligning the panels to get rid of the red/blue ghosts and fine tuned the focus. That part is good. Also the lens throw is much wider, enabling me to fill the screen top to bottom.

The part that fell significantly below my expectations is the brightness, or lack thereof. It's about 2/3 as bright on "high" mode as my decade old IN82 that has over 2000 hours on the original lamp, when in "low" mode. It's so dim in fact that I have problems with ambient light from a computer monitor at the back of the room that I never noticed with the InFocus IN82 because that picture was always bright enough to swamp any ambient light.

The lamp on this Sony has just shy of 2600 hours on it, about what my old projector has, but the brightness isn't anywhere near that of the IN82. Certainly nowhere needed to do HDR and not enough for 3D.

The unit arrived in "high" lamp mode and with the contrast set to max. No matter which mode I use, including "bright TV", I can't get the eye popping brightness of the old projector. And the color gamut isn't any better, either, which surprised me for a PJ that's supposed to handle HDR content.

Is this REALLY 1800 lumens? Next to the 1500 lumens of the IN82, it doesn't seem like more than 600 lumens. The lack of brightness and the lack of color gamut are very disappointing. I realize it's a store demo and I got it for half price of the list price, but even so, it doesn't seem like I'm getting $7500 worth of picture here. When the IN82 is projecting, the whole room lights up like someone opened a window. But the 675 ES is like dim twilight.

Could it be that the lamp is minutes away from expiring? Usually HP lamps turn pink when they're dying. My old PJ is still very bright with over 2000 hours on the lamp. Maybe this lamp is only putting out 500-600 lumens for some reason?

At the moment, I'm driving it with my editing workstation NLE playing DCI 4K footage that I shot in its native 1.9:1 aspect. The other thing that is driving me nuts is that when I shut off the projector and turn it on later on, the computer goes bonkers. All of the monitors connected to it blank out for a minute and when they come back on, my desktop has moved to the projector and my Wacom tablet mapping is mapped to the projector screen and my NLE app has moved from the 'main' display to the projector. My old projector didn't upset the computer when I switched it on or off. This is a major problem for me because it means that I have to use the keyboard to position the app window back to the main monitor and then I have open the Wacom driver app and reassign the active tablet area back to the computer's main display. The whole process takes about ten minutes once I get the hang of it, but it shouldn't be happening in the first place.
 
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