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Title: Projector Lumens vs screen size rules
Post by: Gus Housen on April 07, 2011, 02:19:22 pm
I was wondering what projector sizes are usually recomended with certain sized screens Like 8ft, 10 ft, 12 ft Say in average ballroom ambient light ( I know the ambient light level plays into it Is there a good way to measure that as well to compare projectors?)
Title: Re: Projector Lumens vs screen size rules
Post by: Andrew Welker on April 07, 2011, 03:54:34 pm
I was wondering what projector sizes are usually recomended with certain sized screens Like 8ft, 10 ft, 12 ft Say in average ballroom ambient light ( I know the ambient light level plays into it Is there a good way to measure that as well to compare projectors?)

When I'm designing a projector system, I typically aim for at least 50 foot-lamberts (lumens per square foot) on the screen. You can go lower than that if your ambient light on the screen is lower, but 50 is a good target to aim for.
Title: Re: Projector Lumens vs screen size rules
Post by: Brad Weber on April 07, 2011, 07:22:20 pm
I was wondering what projector sizes are usually recomended with certain sized screens Like 8ft, 10 ft, 12 ft Say in average ballroom ambient light ( I know the ambient light level plays into it Is there a good way to measure that as well to compare projectors?)
The 'recommended' goal is a minimum 10:1 image contrast ratio, meaning the projected image brightness on the screen will be at least 10 times the brightness of the ambient light level on the screen.  Many people get away with lower ratios, I've seen 5:1 and 3:1 examples in real life that were acceptable, but that also leaves little 'fudge factor' for aspects such as decreasing output as the projector lamp ages.
 
There can also be other details that can affect this such as the light loss of the lens if you're using anything other than a standard lens at it's optimal zoom or whether it is front or rear projection.  The screen format can also be a factor if you are going by screen diagonal sizes as a 10' diagonal 4:3 format screen represents a different screen surface area than a 10' diagnonal 16:9 format screen.  Related to that, the relationship of the projector format and screen format can be a factor, for example if you use a 4:3 format projector to fill a 16:9 format screen then 25% of the projected image, and thus also 25% of the overall projector brightness, is above and below the actual image on the screen.
Title: Re: Projector Lumens vs screen size rules
Post by: Niels Hempel on April 12, 2011, 10:45:54 am
I was wondering what projector sizes are usually recomended with certain sized screens Like 8ft, 10 ft, 12 ft Say in average ballroom ambient light ( I know the ambient light level plays into it Is there a good way to measure that as well to compare projectors?)

Projector Central (.com) has a "pro calculator"  where you can choose what model projector you would like to use, then you can adjust projector distance to get the recommended screen size.  Or, put in your screen size and it will give you the distance range.

Hope this helps!
Title: Re: Projector Lumens vs screen size rules
Post by: Arnold B. Krueger on May 13, 2011, 06:38:44 am
I was wondering what projector sizes are usually recomended with certain sized screens Like 8ft, 10 ft, 12 ft Say in average ballroom ambient light ( I know the ambient light level plays into it Is there a good way to measure that as well to compare projectors?)

Don't forget about ambient light. Is there such a thing as "typical" amvient light? I don't think so.

We use a 6000 lumen Panasonic 5500 projector with a screen that must be 20 foot diagonal with fairly high ambient light at times, and it just works. In fact I had to back off features like "digital brilliance" to keep a nice, easy-to-read presentation.
Title: Re: Projector Lumens vs screen size rules
Post by: Brad Weber on May 13, 2011, 08:19:18 am
Don't forget about ambient light. Is there such a thing as "typical" amvient light? I don't think so.
Coincidentally, InfoComm recently presented a proposed Image Contract Ratio standard, which would be issued as an ANSI standard, for public review and from what I saw complying with that standard could impact many people.  Not only is the process of measuring and documenting both the ambient light levels on the screen and the projected image brightness on the screenn very specific, but the contrast ratios recommended are greater than the 10:1 ratio often recommended in the past with 15:1 and 30:1 apparently being recommended for many common tasks and up to 80:1 for some critical tasks.
 
This would not be a mandatory standard, so no one has to comply, however for professionals such Standards may well be considered to define 'industry standard practice'.
Title: Re: Projector Lumens vs screen size rules
Post by: Jordan Wolf on May 13, 2011, 04:04:47 pm
That's cool, Brad.  I'll have to keep track of that.
Title: Re: Projector Lumens vs screen size rules
Post by: john sanders on May 23, 2011, 06:53:31 pm
projectorpeople.com