Originally Posted by rtchinn
There is no "theoretical" limit on the image size... it's simply a matter of this:
Image Brightness = available lumens divided by screen area.
With an 80" diagonal screen, the image will cover an area of 19 square feet. The 1400 'effective' lumens is spread out over that 19 sq.ft. and the resulting image will be 36 fL.
On a 150" diagonal screen, the image will cover an area of 66.7 square feet... that's 3.5 times as much screen area to illuminate with the same 1400 lumens... so your resulting image will be about 10 fL link to calculator.
The lens has the capability to reach "infinity focus", so as I said, there's no theoretical limit on screen/image size... it's simply a matter of ever diminishing image brightness due to spreading your "available lumens" out over a larger area. I've used this projector outdoors on a >200" canvas screen, and it's still enjoyable... but that was in near pitch-darkness, and not "home theater" conditions where I'd expect higher image quality.... sometimes referred to as "pop", where the image has sufficient brightness to stimulate the viewers adequately... which most engineers say is no less than 12-13 fL.
BTW... LED and Laser projectors from LG (and most others) are not rated in "real ANSI lumens", but rather . This is due to not having a "color wheel" as typical DLP projector have. If you read about "Color Light Output" ratings in projectors you will understand this better.
It boils down to this..."normal" lamp-based/color-wheel DLP projectors have the technical ability to output non-color-wheel-filtered light to the screen. They do this by providing a "clear" section in the color wheel, which gives them a time slot to output un-filtered light, with the full light spectrum of the arc-lamp. This is good for classrooms and business presentations where extra brightness is required, and color was less important (this is the market that DLP projectors were originally designed for... not Home Theater).
This creates an artificially high "ANSI Lumen" rating, because that old rating system was based strictly on a White and Black checkerboard pattern... no "true image colors". Also, the "White" color is not even specified, so the manufacturer can output any "White" color they want - and due to the uneven light spectrum of a typical Metal-Halide "HID" or "" lamp, it's usually far from the D6500 CIE specification.
Three-chip LCD (and 3-DLP) projectors have been at a disadvantage in the "specsmanship" war ever since... because they do not have the ability to output "unfiltered" white light, since all light goes through the permanent color filters on them... Red/Green/Blue.
Maybe someday the industry "projection review engineers" will create a "Calibrated Color Brightness" standard, where the projectors are required to output a well defined spectrum of balanced colors... that will put everybody on level ground for true comparisons... and LED projectors will finally shine bright in "specsmanship".
This article addresses this issue:
After calibration, the calibrated brightness achieved was 763 lumens in brightest mode. This was plenty to light up a 120" diagonal image on a 1.0 gain screen in a darkened room with very good color, contrast, and shadow detail. Lowest brightness mode cut lumen output by about 45% to 422 lumens. This is still plenty for a 92" to 100" diagonal image if a low gain screen is used. The medium brightness setting falls right between the two with 583 lumens falling on the screen."
That "763 lumens" mentioned would be what I called a "Calibrated Color Brightness"... "real world home theater" type color calibration.
BTW... the LED lifetime in the PF1500 is rated for (as you noted) 30,000 hours. While "theoretical" LED lifetime is rated at full brightness, there are other issues at-play. When ran at full power, there is significantly more heat generated in the unit. While the cooling fans do run at increased speed to help this condition, the heat is still much higher... and many electronic components are therefore exposed to this elevated operating temperature, which shortens their lifetime... even LED's. At a bare minimum, I always recommend running "high altitude" option as ON, to run the cooling fans at maximum speed to help cool things down as much as possible. I run my PF1500 at Medium power (Medium Energy Savings), and still run "High Altitude" setting ON.
I purchased my unit as a "DOA" unit, it was not working as a result of an overheated component that I had to replace. Now... while it's possible that this component was defective when new, the exact same symptoms my "dead" unit exhibited (before repair) have been mentioned by many other owners of PF1500's that have failed... and unfortunately after the warranty had expired. (I still hope to find more like mine that I can repair, and use for further upgrade experiments I have planned... I can't use my unit for experimenting and for family entertainment simultaneously)
The first upgrade project I have planned is determining why it's not possible to get a "full-screen focus"... there is always some compromise needed to reach a "usable focus" with these projectors. I'm confident I can resolve it, but it's something that will take significant research and time. If I had not had many other projectors prior to this, I may not have noticed the deficiency... but it's FAR from "home theater" image quality in my mind... but it does have the DNA in the design to reach that level... it's just that LG didn't care to press the optical engine manufacturer for that last 20% of possible image quality.
Also on my list is to improve the "real world" contrast ratio... it's nowhere near the rated 150,000:1 "specsmanship" published numbers... it's more like 300:1, or even less (real world, personally measured). There are multiple issues at the root of this problem, some are easily solvable (like my external snap-on lens mask that I make to eliminate light-spill onto surrounding surfaces), while others require internal lens mods... of which I've determined at least 2 of them are resolvable... but require internal lens mods.
Thanks for the detailed info.
I built an anamorphic lens and a 2.40:1 screen so that I could get the most out of my old LG HS-201 with its limited pixels and brightness. My lens is similar to the one on zuggsoft.com/theater/prism.htm. The projector is connected to a Win7 PC and is mainly used for widescreen movies. The lens worked really well but was tricky to align and (due to a very low loft ceiling) would get bumped out of position by unfortunate visitors.
Now that I have the PF1500 I am debating whether to remove the anamorphic lens and move the projector further from the screen and limit the resolution (from the PC) to 1920x800. Thus the new projector would be permanently 2.40:1 - but I will not be using about 25% of the pixels and It will be further away from the screen - so reducing the brightness.
I used the calculator that you linked to (see calculation images attached) and it shows 51 FL for the 16:9 vs 28 FL for the widescreen. This seems like a big drop. Am I missing something? Will it still be bright enough?
Happy to hear your thoughts about which approach is better: Anamorphic lens using all the pixels of the PF1500W vs. widescreen resolution/further from screen/less pixels.