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Easy Calculator for Screen & Image Size

post #1 of 27
Thread Starter 
This simple, user-friendly calculator may be helpful to anyone planning to buy a screen. The calculator lets you specify the screen size (diagonal, width, or height), the screen aspect ratio, and the frame (or border) width. The calculator then computes the viewing area dimensions, as well as the total screen height and width including the frame or border. It also lets you see at a glance the image height, width, diagonal, and area for five user-modifiable image aspect ratios when projected onto the specified screen.

The calculator is provided in two versions, one for use with MS Excel (preferred) and a second for use with the less capable, but more widely distributed, MS Works Spreadsheet. Either version will also run in the spreadsheet portion of Open Office, a free download. Your comments/criticisms are invited.

ETA- Thanks to member 1canuck2 for adding to the Easy Calculator to include calculating how the screen fits onto your screen wall. See post #25 below for this more comprehensive version of the calculator.

 

Screen & Image Size Calc (Excel).zip 5.1513671875k . file

 

Screen & Image Size Calc (Works).zip 4.58984375k . file
post #2 of 27
Thank you very much for putting this together!
post #3 of 27
Very nice, Thank you!
post #4 of 27
Thread Starter 
Thanks, guys! And a special thanks to Tryg- Your reviews guided me through my first screen purchase a year ago, a Da-Lite High Power with which I could not be more pleased.
post #5 of 27
That is awesome. Thanks for making that available.

post #6 of 27
Very nice! Easier and more straightforward than using an online Pythagorean Theorem calculator. Thank you FLBoy.
post #7 of 27
Thanks for sharing!
post #8 of 27
Your All Screen Gain Calculator (“SGC”) and Easy Calculator for Screen and Image Size (“ECSIS”) are quite useful (I created a similar screen size calculator before discovering yours and it proves the math. However, your format is much better, and the use of Excel’s protection and error condition features are very clever). Now to my point - as I attempt to tie screen size, gain and ft lamberts together. Let’s assume:

1) 35.88 sq ft screen size (default from the ECSIS at B12).
2) 2.07 screen gain (default from the SGC at J30).
3) 531 calibrated lumens (from http://www.projectorreviews.com/epso...erformance.php – Theater Black with low lamp power).
4) Ft-lamberts = lumens / screen square footage x gain.

Then calculated Ft-lamberts become(s):

(531 / 35.88) * 2.07 or 30.63 ft-lamberts

Do you agree with the forgoing?

Assuming (again for illustration) the ideal is 16 ft-lamberts (from http://en.wikipedia.org/wiki/Footlambert), and that all factors above are fixed other than gain, one should shoot for a screen with gain of ~1.1 calculated as follows;

(16 / 30.63) * 2.07 or 1.081 (~1.1)

Do you agree?

I also understand that much more goes into the selection of a screen as additional factors come into play (i.e. ambient light), but I wanted to pause and see if I am on the right track.

Thanks
post #9 of 27
Thread Starter 
jmdore- Thanks for your comments. I agree with your example calculations, but I am a bit confused by your use of my default values. You will, of course, need to enter the geometry of your own setup into the gain calc, and your own screen size and AR into the easy calc.

Other than that, I have a comment about brightness. IMO, it is better to start off with more than 16 fL, because the PJ lamp will dim substantially with age. Some people use an ND filter to dim the PJ when the lamp is new, and then remove the filter after the lamp has aged. Personally, I like a bright picture, so I don't use a filter even though my picture currently is way brighter than 16 fL.
post #10 of 27
FLBoy:
I have had my potential screen estimated by Millerwill to be about 25 ftL. I noticed that you mentioned YOUR screen to be "way brighter than 16 ftL." I believe that I can understand ftL a little better than "screen gain." As such, do you think that 25 ftL is about roughly equivalent to an average plasma unit (I know...what's an AVERAGE plasma unit? ) but just trying to get a better feel for ftL ! Can you elaborate? Thanks.
post #11 of 27
Thread Starter 
Hey WOLVERNOLE- IIRC, plasma screens are about 50 fL. Apparently that's what is required for use during daytime with the shades/blinds/draperies open.
post #12 of 27
FLBoy - I used your default values a) to further my understanding, and b) for the benefit of others that might be tracking this thread (i.e. tracks exactly to your spreadsheets). I will plug in the appropriate values for geometry and screen size (into the respective calculators) once I am ready to do so.

As this is my first projector (Epson 7500UB on order), and as I haven't selected a screen yet (various samples requested and in transit), I'm trying to get "immersed" as much as possible so I can make an informed decision (debatable). Leaning towards the Carada BW (just received the specs via email) based in part on your recommendation in another thread. Much like you, I also lean towards a brighter picture.
post #13 of 27
Leaning towards the Carada BW (just received the specs via email) based in part on your recommendation in another thread. Much like you, I also lean towards a brighter picture.[/quote]

Just remember that the Carda BW is realistically NOT a 1.4 gain screen, but as many have often reminded others on AVS, the BW "shows" at ~ 1.1-1.2
It is pretty close to neutral.
post #14 of 27
The Carada website claims 1.4, today's email (from Carada) reiterates the 1.4 gain, the threads here suggest otherwise... while Carada also seems to generally be well regarded. Samples are on the way - hopefully they are large enough (from Carada and others) to be able to make a meaningful subjective evaluation.
post #15 of 27
Quote:
Originally Posted by jmdore View Post

The Carada website claims 1.4, today's email (from Carada) reiterates the 1.4 gain, the threads here suggest otherwise... while Carada also seems to generally be well regarded. ....

Okay.
post #16 of 27
Thanks FLBoy. Excellent work on excel formulas! Love that program.
post #17 of 27
Quote:
Originally Posted by FLBoy View Post

Hey WOLVERNOLE- IIRC, plasma screens are about 50 fL. Apparently that's what is required for use during daytime with the shades/blinds/draperies open.

Plasmas at 50fl are really pretty dim. My 4 year old 70" rear projection was measured in reviews at 130fl! Most lcd flat panels are brighter than plasma too. But with the lights down I prefer the plasma. No contest.
post #18 of 27
Echo the above thanks a lot for setting up this great tool. Allows me to keep tinkering with screen size instead of just doing anything : ^)
post #19 of 27
A Newbie question. I want to install a FP. Our seating will be about 10' from the screen. What is the maximum screen I should get? I am also open to projector recommend ions.
Thank you
post #20 of 27
Thread Starter 
It's basically user preference. I sit about 12.5 feet from my 100" 16:9 screen. It seems about right, but I could stand a bit larger if the room would accommodate it. If you watch mainly 2.35:1 scope movies, then a bit wider screen probably would be better.
post #21 of 27
Thread Starter 
I have upgraded the Excel version of the calc. You now have a choice of using the diagonal, the width, or the height of your viewing area to specify your screen size. Generic descriptions of popular aspect ratios have also been added to the image size section to help our noobs. I have not changed the MS Works version of the calc, as it is incompatible with some of the improvements I have made. The upgraded version is in post #1.
post #22 of 27
Thread Starter 
OK Guys. I got over my spell of laziness and upgraded the Works version of the calculator as well. Both the Excel and Works versions of the calculator now allow entry of diagonal, width, or height to specify size of the viewing area, making it easier for those of you with width or height limited installations. Both also add a generic description to the default image aspect ratios to aid those who may not recognize the numeric ones.

The Works version has two drawbacks. It lacks cell protection, so you will need to be careful not to overwrite the formulas, and it sometimes fails to recalculate after an entry is modified. I have no idea why. You can sometimes wake it up by clicking on one of the calculated values. Relaunching the calculator also works. Enjoy!
post #23 of 27
thanks u very much for sharing these information.
post #24 of 27
thank you very much for putting it together..

addi
post #25 of 27
I hope OP doesn't mind, but I modified his spreadsheet to include screen position on the wall info.

I added a Screen Height Calc and Screen Width Calc section that allow you to enter the dimension of your screen wall, the front row eye height, and the eye position relative to the screen. These sections output The Screen Top to Ceiling, Screen Bottom to Floor, and Screen Left/Right to Wall for your screen both with and without the frame. I modded the spreadsheet for me, but then assumed other peeps might like this info too...

I rev'ed the spreadsheet to 1.2.2

Robin

 

Screen & Image Size Calculator V 1.2.2 (Excel).zip 5.8427734375k . file
post #26 of 27
Thread Starter 
Quote:
Originally Posted by 1canuck2 View Post

I hope OP doesn't mind, but I modified his spreadsheet to include screen position on the wall info.

Not at all. That's why I did not lock it with a password.

I would prefer to keep the simpler version in the OP. (Don't want to frighten off our noobs.) I'll reference your more comprehensive version there as well.
post #27 of 27
Found it again .
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