Hi,
I am about to order either the Panny 200u or the Epson HC 720. Both are "bright" projectors with lots of flexibility. My room is rectangular. The optimal place to mount would be the short way (for room setup), giving me just a slightly longer than 10ft throw. Going the other way (a 16ft throw) is an option, but will be much tougher to arrange the furniture.

I really want to get at least a 100" screen. However, if I go the 10ft throw route, in order to get a 100" image, I'd be looking at just about maxing the zooming capability of the projector. My question is: Does going with a full zoom worsen my Picture Quality or shorten the bulb life? If that is the case, I'd rather sacrifice the layout of the room and get the best picture by going the other way.

Any thoughts?

Thank you!

Full wide angle could make the image a bit softer, but, whether or not you notice will depend on how good your eyesight is and how picky you are. I have my HD70 at full wide angle and I'm happy with the results.

Our PJ lens forward edge is 11.5 ft from the screen and we get a 120 inch diagonal image with a good bit of zoom capacity remaining (Panasonic AE-900U). We sit about 12 feet eyeball to screen.

My personal opinion is if I stand about 8 ft away the image is still smooth and sharp but @ 120 inches I am almost too close for viewing comfort.

If you can sit 10 ft away and throw distance is 10 ft away with a zoom of at least 1.6 you should be okay @ 100 inch diagonal and get a good WOW Home Theater experience. Our panasonic has a 2.0:1 zoom spec. Our Canon has a 1.6:1 zoom range and at max wide angle it did over 100 in diagonal at10.5 ft throw.
goodluck

My question is: Does going with a full zoom worsen my Picture Quality or shorten the bulb life? If that is the case, I'd rather sacrifice the layout of the room and get the best picture by going the other way.

Because of the way the optics are designed in most PJs, you'll get a brighter image/worse contrast at the max zoom (PJ close to screen), and a dimmer picture/better contrast at min zoom (PJ far from screen). In addition, since you're using less of the edges of the lens at min zoom, chromatic abberation can be less (assuming it's a problem at all). Bulb life would not be affected either way.

Whether or not you'll be able to notice these differences is another question however. That depends on you and the specific PJ.

Because of the way the optics are designed in most PJs, you'll get a brighter image/worse contrast at the max zoom (PJ close to screen), and a dimmer picture/better contrast at min zoom (PJ far from screen). In addition, since you're using less of the edges of the lens at min zoom, chromatic abberation can be less (assuming it's a problem at all). Bulb life would not be affected either way.

Whether or not you'll be able to notice these differences is another question however. That depends on you and the specific PJ.The brightness difference between the extremes can be calculated knowing the fstop range of the zoom lense, but what's the causing the contrast difference?

It has to be the same reason that a manually adjusted internal iris can improve contrast at the expense of brightness. I've never read a definitive reason why that tradeoff between brightness and contrast exists, but one theory I saw was that light scatter in the optical engine causes black and white levels to grow non-linearly. In other words, it causes inefficiencies that result in having to raise black level floors 15% in order to get a 10% increase in white level ceilings. I just made those numbers up, but it illustrates the point.

I don't know for a fact whether that theory is 100% accurate, but it makes sense since a fixed iris has been proven to increase contrast as it reduces brightness. Furthermore, brightness reductions done outside the optical engine (for example using an ND2 filter) do not change contrast ratios, so the reason has to lie within.

Just as an example of a typical difference you may see in brightness/contrast between max/min zoom, here is what cine4home measured on the IN76:

Lumen/Contrast Table - IN76
Zoom Lumen (@ D65) Contrast (@ D65)
Max zoom: 800 (Hi-mode) / 580 (Eco mode) 1500:1
Min zoom: 690 (Hi-mode) / 500 (Eco mode) 1800:1

http://www.cine4home.com/reviews/projectors/InfocusIN76/IN76Review.htm

JeffKB:

Interesting theory. Based on the numbers from cine4home, I don't think much is lost in perceptable change in contrast, i.e., it's not like it got cut in half. I think the pros of having the projector close to the screen would usually outweigh the cons. The pros being a brighter image and not putting a shadow on the screen everytime somebody stands up for another beer or going blind from getting hit in the eye with a bright scene(assuming a ceiling mount). Also, like you said, closing down the iris has a similar effect, so if you maintain the same lumens on the screen, then you can use a smaller iris opening when you are closer to the screen. I wonder if cine4home's numbers are with a constant iris opening or with a constant lumens?

Also, like you said, closing down the iris has a similar effect, so if you maintain the same lumens on the screen, then you can use a smaller iris opening when you are closer to the screen. I wonder if cine4home's numbers are with a constant iris opening or with a constant lumens?
The IN76 does not have an iris, so those measurements just reflect the effect of zooming.

I agree with you about not necessarily worrying about the differences. In most cases it probably wouldn't make for that dramatic a difference, and installation considerations become more important.