ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Pro AV Forum => Topic started by: Andersongates on May 02, 2013, 10:02:53 pm

Title: Projector throw equation
Post by: Andersongates on May 02, 2013, 10:02:53 pm
Rookie question...I want the straight out math equation for figuring out lens ratios and projection distances.  I've looked everywhere but all I seem to find is manufacturers throw distance 'calculators' that do it for you per projector model, but I don't want that.  I have a wide variety of projectors but lenses are all the same. .8, 1.2-1.8, 2.2- or etc....

Hope someone knows it
Title: Re: Projector throw equation
Post by: Mac Kerr on May 02, 2013, 10:20:14 pm
Rookie question...I want the straight out math equation for figuring out lens ratios and projection distances.  I've looked everywhere but all I seem to find is manufacturers throw distance 'calculators' that do it for you per projector model, but I don't want that.  I have a wide variety of projectors but lenses are all the same. .8, 1.2-1.8, 2.2- or etc....

Hope someone knows it

The lens' screen ratio it the ratio of the screen width to distance. A .8 lens will make a 10' wide image at 8'.  A 1.2-1.8 zoom will make a 10' image at 12-18'. The lens ratio depends on both the lens and the projector.

Mac
Title: Re: Projector throw equation
Post by: Andersongates on May 02, 2013, 10:39:22 pm
Easy....thank you very much
Title: Re: Projector throw equation
Post by: Brad Weber on May 03, 2013, 07:02:50 am
Also keep in mind that almost all projector manufacturers now offer projection calculators on their web sites that will show not only throw distance versus image size with various lenses but also other related factors such as the related vertical offset and allowable lens shift.  The relationship of throw distance, image size and brightness are also available for many projectors and projector/lens combinations on ProjectorCentral.com
Title: Re: Projector throw equation
Post by: Jordan Wolf on May 03, 2013, 11:41:39 am
It should also be noted, similarly to Brad's post, that some lenses will be marked with different specs based on the resolution and/or aspect ratio you at projecting at.

I know the short-throw lenses we use with the Christie Roadster series function in this manner.
Title: Re: Projector throw equation
Post by: Kyle Malenfant on May 04, 2013, 12:10:17 am
Here is a great tool that I use all the time for calculating throw distances.  It's especially helpful to me if I need to rent additional projectors but am unfamiliar with their throw. 

I usually keep the zoom in the middle on the calculator and use that as my measure point.  From there, on the job, you can zoom in or out to compensate for whatever variability the calculator is off by.

http://www.projectorcentral.com/projection-calculator-pro.cfm
Title: Re: Projector throw equation
Post by: James Feenstra on May 05, 2013, 06:41:43 pm
There's an ap for that :)