To much lens shift?

[leo1058]

Need some advice. I have 8ft ceilings, my screen is centered half way on the wall. Throw distance is 11ft , sitting 9ft. Projector is ceiling mounted on an 8inch mount. I have to use a lot of lens shift to get it where i need it. Does to much lens shift hurt PQ. Thanks

 

[indulger]

The vertical side(s) may be slightly angled due to this, but if you zoom out the pic slightly to expand on the side of black material, you may not notice. I have the same problem because a ceiling fan is right where the projector needs to be, but the wife said I couldn't move the fan.

 

[leo1058]

I have the same problem (wife & fan), thanks for the advice.

 

[BMXTRIX]

Do NOT TILT YOUR PROJECTOR!!!

You need to measure things and then use lens shift as appropriate. The center of the lens should be close to the center of the screen (left/right) and near the top of the screen or up to a couple of feet above the top depending on the projector.

KEY WORDS: DEPENDING ON YOUR PROJECTOR!

DLP projectors tend to throw an image significantly downward when ceiling mount. About 33% of the screen height is common (depending on your projector!) and so a 48" tall image (about 100" diagaonal) would have that lens about 16" above the top of the screen.

LCD projectors, most notably the Epson 8350, 8700UB, and Panasonic AE4000 include lens shift. Lens shift has a range of motion, and anywhere in that range you should not have serious image degradation occur. The Epson has tremendous lens shift, typically about 100% of the image height. So, if the screen is 48" tall, you could put the lens up to 48" ABOVE the top if you wanted/needed to. So, it all comes down to exact numbers.

How far above the TOP of your projection screen do you want/need the lens of the projector to be?

How big is your screen?

What projector are you planning to get?

 

[jostenmeat]

Do NOT TILT YOUR PROJECTOR!!!

Can you please explain why? Thanks!

My adjustable pipe does not go high at all, because it was chosen to be coupled to my previous screen, a retroreflector.

Now that I have a different screen, I wanted to increase its ANSI contrast by using some more vertical shift, and so I tilted the PJ just slightly, rough guess of 5-10 degrees by eyeballing. See, I am already at the highest position on the pipe.

I can easily set it even again. I just don't want to buy a new pipe and deal with that stuff again. Cheers.

 

[BMXTRIX]

I'm saying it a bit wrong - you can tilt a projector a bit, but never use keystone correction.

When you use keystone correction you actually take your square image and project at a keystone shape. You not only give up resolution of your projector, but you give up brightness.

More importantly, you are significantly distoring a proper 'rectangular' image onto a diagonal projection pattern. This isn't actually possible for a projector to do perfectly, under any circumstances, so there is a falloff in image quality.

It may appear minor, and in truth, projectors have gotten much better at this in the last few years, but this distortion is real and unavoidable if digital keystone is used.

It is FAR better to always get a projector where it should be mounted, and one of the reasons why projectors with lens shift are so phenomenally important to first time projector users.

 

[indulger]

That's what i was speaking about. My projector isn't exactly centered; slightly off. I use lens shift on my epson to get it centered but this gave it a slight keystone effect on the left side. So i zoomed out just a hair to stretch the picture out barely on the masking and you can't tell it.

 

[lsiberian]

I'm saying it a bit wrong - you can tilt a projector a bit, but never use keystone correction.

When you use keystone correction you actually take your square image and project at a keystone shape. You not only give up resolution of your projector, but you give up brightness.

More importantly, you are significantly distoring a proper 'rectangular' image onto a diagonal projection pattern. This isn't actually possible for a projector to do perfectly, under any circumstances, so there is a falloff in image quality.

It may appear minor, and in truth, projectors have gotten much better at this in the last few years, but this distortion is real and unavoidable if digital keystone is used.

It is FAR better to always get a projector where it should be mounted, and one of the reasons why projectors with lens shift are so phenomenally important to first time projector users.

Just had to fix this in our youth room. The guy before had angled the thing from a platform like 30 degrees and keystoned it like a madman. It was this terrible small picture. He didn't realize you could flip the projector over lol.

Please for my sanity never keystone 30 degrees.

 

[BMXTRIX]

That's what i was speaking about. My projector isn't exactly centered; slightly off. I use lens shift on my epson to get it centered but this gave it a slight keystone effect on the left side. So i zoomed out just a hair to stretch the picture out barely on the masking and you can't tell it.

If you have a slightly keystoned image after using lens shift, then your projector is not square to the screen and if you have lens shift left, then you can correct this.

99% of people do NOT know how to properly setup a projector with lens shift.

You aim the projector square to the screen - not at the center of the screen, but square to the screen itself.

Then use lens shift to put the image on screen. If one side (left, right, top, or bottom) is larger than the other, then you need to turn the projector away from the larger side, then use lens shift again to get the image on screen.

Keep moving the projector until the image is square and even on all sides and level.

Then do the final lens shift, zooming, and focus to get the image perfect on screen.

I had a client walk out of the room visibly upset because I would setup his Panasonic and see that it was keystoned, and I would tilt or twist the projector to get rid of the keystone, then the image would go off screen (making him upset), then I would use lens shift, and get it back on screen (he would be happy), then I would see what was keystoned still, so I would twist the projector a bit more (making him upset), until he finally left the room so upset that I wouldn't just leave the image bending outward a couple of inches on one side. Took me about 15 minutes to do, but he was just not able to cope with it and didn't understand that it is the proper way to setup a projector.

It - is - the - proper - way -to - setup - a - projector!

Of course, some projectors don't have lens shift, or don't have enough for your 'requirements', and then I just shake my head and watch as people use lens shift. So, that's when I get aggrevated and walk out of the room!