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Topic: is lens shift an imortant option?
Joined: Mar 31, 2005
Lens shift can help. If you are buying a first projector, I think it is a little less important. Why? Because you can set up your screen to match the projector. If you are buying a projector as an upgrade, then every feature that allows you to match the projector into your existing setup with minimal trouble is helpful. Lens shift allows you to compensate for different offsets, just like zoom allows you to compensate for different distances to the screen.
The Panasonic AE700 is known for its adaptability in setup. While my Infocus 4805 is known for a rather large offset and narrow zoom range, making installation trickier.
Joined: Mar 29, 2005
If you are ceiling mounting your projector as part of a permanent installation, then I think lens shift is less important because you only have to set it up once. If you will be using the projector on a table for portability, then I think lens shift becomes an important option.
Joined: Mar 28, 2005
More specific on what lens shift actually is:
When you point a projector straight ahead at a wall, you get a perfectly rectangular patch of light on the wall.
Where that patch of light falls is where you will put your screen. Except, you may not want the screen there, so you want the screen 2 feet higher than where the rectangle falls on the wall.
Solution: Point the projector up so the rectangle is higher on the wall!
Problem: The rectangle turns into a trapezoid because you are angling it, you may remember this from the overhead transparency projectors from when you were in school. To get the image way up on the screen, the top stuff is really wide, the lower stuff is really narrow.
Solution to trapezoid issue: Use 'keystone correction'. This uses less of the resolution of the projector and reformats the video when you project at an angle like described above.
Problem: When you use less of the projectors resolution AND reformat the video you end up making the video look really, really bad. You do not want to use keystone correction on a projector AT ALL COSTS!!!
Another solution: Keep your projector perfectly level so the image stays square, but lift your projector two feet higher!
Problem: Your projector is now free floating 5 feet off the floor in the middle of your room and you don't want to put a table there or put books under it to mount it there.
Real solution: You flip the projector upside down and mount it from a pole about 6" off the top of your ceiling. The projector remains perfectly flat, the image is now about a foot higher than you want it.
Lens shift moves the actual lens optics (several pieces of glass inside the projector) so that the light is directed lower onto the wall. You spin a dial on the projector to manually move those optics until the image is exactly where you want it on the screen.
This is called vertical lens shift.
Now you are ready to mount your projector... only you notice that where you totally want to mount your projector there is one of your homes air-conditioning vents! Dang, need to put the projector about 8 inches to the right.
Solution: Don't twist or turn your projector! Just spin another knob and the image moves to the left or right. Just as with vertical lens shift, only this is horizontal lens shift and allows you to get that image exactly where you want it.
DO YOU NEED IT?
Well, no. I don't have it and the last two models of the cheaper Panasonic projectors didn't have it. You flip the projector upside down, put it on a ladder in the middle of the room and find out exactly where it should be mounted and how far off the ceiling it needed to be. Then get a pole and mount it EXACTLY in the right position. This took me all of 15 minutes to figure out. I used a 12" pole from Home Depot and had it up really quick - no problems at all.
Disadvantage to lens shift? None that I am aware of really. Lens shift is used in some very serious photography equipment to shoot off angle - like tall buildings from the ground. But, quite often as you reach the far limits of lens shift you are getting near the edge of the optics inside the lens and the image on screen may suffer a little bit. Just don't use the final 5% of range that you may have and this shouldn't be an issue.
Pay more for it? Absolutely, if you want it or need it! For me, I want my next projector to be mounted right up against the wall if possible, so I will get a projector with lens shift for sure.
- Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.
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