Help Me Understand The Projection Calculator Please - AVS Forum
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post #1 of 7 Old 03-19-2013, 04:20 PM - Thread Starter
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Backstory: I have an Infocus X10 (DLP Projector, circa 2009). Would like to replace it with a newer display unit. Looking into the BenQ W1070. Went to Projectorcentral.com and pulled up both units to compare. Things don't seem to add up. Specifically I was looking at what light output the new BenQ would have. So I set up both calculators to have the same output screen size, same gain, and max zoom (to maximize the light output of each).

The question is, please explain the following:

Infocus X10. 1200 Ansi Lumens, Projecting 100" screen. Image Brightness: 49 FL.

Benq W1070. 2000 Ansi Lumens, Projecting 100" screen. Image Brightness: 40 FL.

Wth?

Links to both calculators:

http://www.projectorcentral.com/InFocus-X10-projection-calculator-pro.htm

http://www.projectorcentral.com/BenQ-W1070-projection-calculator-pro.htm

Am I missing something?

I don't mind if the BenQ is a tick too bright for my room because I'd actually like to add a little ambient light. So, if it's a bit too much, that's ok. Also, I'll be projecting a larger image with the BenQ if I get it, probably 135" or so. So, F-L will drop some. From the numbers they are showing, and prior experience with my current setup, I'd almost be worried about it not being bright enough!

The lenses are very similar aperture ranges, output wattage seems very similar. Either I'm missing something, or the calculator is hosed... I do know that from a screen size standpoint on the X10, it is spot on.


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post #2 of 7 Old 03-19-2013, 06:47 PM
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I agree,

the calculator seems flawed. Yesterday I used it to compare the image brightness of my projector on 3 potential screens measuring 119", 110", and 100". The calculator indicated the brightness for the 3 screens (using same projector distance and screen gain) would be 17 fL, 17 fL, and 19 fL, respectively.

This did not seem right to me, so I did the math on my own and determined the actual image brightness would most likely be 14.8 fL, 17.2 fL, and 21 fL. This makes sense to me, and casts doubt on the accuracy of that calculator.

Of course, in your case, the calculator could be using different lumen values based on different picture modes for each projector (e.g. assuming the brightest mode for the InFocus and a dimmer mode for the BenQ.) My projector is a Panasonic PT-AE8000, which is rated at 2400 lumens, but the ProjectorCentral calculator seems to be using a lumen value of about 800 for its calculations, which is certainly closer to a real-world value. One flaw of the calculator is that it does not reveal what lumen level it is using in its calculations.
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post #3 of 7 Old 03-19-2013, 06:59 PM
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Quote:
Originally Posted by Aesclepius View Post

the calculator seems flawed. Yesterday I used it to compare the image brightness of my projector on 3 potential screens measuring 119", 110", and 100". The calculator indicated the brightness for the 3 screens (using same projector distance and screen gain) would be 17 fL, 17 fL, and 19 fL, respectively.
This did not seem right to me, so I did the math on my own and determined the actual image brightness would most likely be 14.8 fL, 17.2 fL, and 21 fL. This makes sense to me, and casts doubt on the accuracy of that calculator.
The zoom level affects the lumens that the projector outputs, so I doubt they would line up at 14.8, 17.2, 21 which seems to be approximating equal brightness spread over the different areas (Zoom higher/larger picture has higher total lumens than Zooming to smaller picture or projecting the same size image from further back)... However, I don't know if they make the calculator adjust for this differently for every projector-- or if It possibly follows the same formula for every projector as an optical property of how zoom lenses work. Maybe someone else would have a more authoritative comment on that.

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Originally Posted by Aesclepius View Post

One flaw of the calculator is that it does not reveal what lumen level it is using in its calculations.
This is a good point. It also allows picking between "Presentations", "Data/text" and "Video/Games" and doesn't show the different brightness values used for each calculation.

For all the projectors I have tried, it exactly doubles the calculated image brightness if you select presentations or data/text compared to video/games. It seems like something is wrong with the base value it uses for one of those 2 projectors.
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post #4 of 7 Old 03-19-2013, 07:27 PM
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Originally Posted by JustAnEE View Post

However, I don't know if they make the calculator adjust for this differently for every projector-- or if It possibly follows the same formula for every projector as an optical property of how zoom lenses work. Maybe someone else would have a more authoritative comment on that.
For all the projectors I have tried, it exactly doubles the calculated image brightness if you select presentations or data/text compared to video/games.

His calculator uses a logarithmic formula for determining brightness across ZOOMs, which is fine, but the problem with that calculator has always been that he does not reveal the baseline lumens. I've noticed there are times where he uses about half the MFR's brightest-mode number because he probably did not have a measurement to go by. Otherwise, it seems he uses a living room type mode for most projectors. Some of his measurements are accurate, some are not, you just never know.

I made a calculator in my signature which reveals it, but the problem with my calculator is I stopped developing it on version Beta 0.2, and there are some lens shift bugs. One day I'll get back to it. So no calculator is perfect. You can however go to www.projectorreviews.com and use his LUMENS numbers to plug manually into my calculator and get a more accurate idea of how bright a projector really will be.



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for both one projector or dual stacks

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post #5 of 7 Old 03-20-2013, 06:19 AM - Thread Starter
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Thanks for the responses guys. Ok, so perhaps I'm learning something. So, Ansi lumens, which I thought was an accepted standard of light output, doesn't really translate to the real world? Not linear anyhow? I can understand the numbers not being perfect. But in this case, a projector with 66% more ansi lumens has 18.5% less light output. That's a big swing. I guess I was under the impression that the ansi numbers were something I could trust with relative security. Evidently not. Same with Ansi Contrast, I don't understand how that works either. measured numbers are no where near what they claim. That BenQ is rated at 10000:1, but measures 4700 supposedly, and I read that many people don't even believe that. confused.gif

I did send a message to Projector Central last night asking about this. I haven't gotten a response back yet. I'll be interested in what they have to say. I'll use Coderguy's calculator with numbers from the site linked and go from there for the time being. Maybe I'll learn something more while doing that exercise.

Thanks again!
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post #6 of 7 Old 03-20-2013, 07:55 AM
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The reason the projectors drop so much is because depends on mode, zoom, setup, and a lot of it on calibration and lamp age.

That said...
A lot of the manufactures quote the theoretical brightest mode of the projector that is possible with the build they used. The problem is theoretical Lumens is not always how it came out in their final product for various design reasons. They are essentially quoting what engineers told them was the maximum you could get out of that hardware from that wattage lamp that is in use.

Some MFR's are more careful (JVC doesn't usually exaggerate this much), hence JVC probably quotes brightest mode numbers from measuring post-build or a tech testing room rather than using purely theoretical numbers. Optoma used to exaggerate this sometimes on some projectors pretty bad.

Projectors are so much brighter now-a-days and so much better.



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post #7 of 7 Old 03-20-2013, 08:37 AM - Thread Starter
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I checked on the site coderguy linked and the numbers there, measured, on both units were about 900 for mine and about 1750 for the BenQ. that's more in line with the ansi figures in the marketing/technical specs.

I don't see a lot of people saying to stay away from the BenQ, so that may be the route I go. Won't happen immediately but I'm going to have a new display. I wanted to stay brand loyal to Infocus, as they've been good to me. I have to do some more shopping on their stuff, but at this price it seems the W1070 is tough to beat.
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