Full Version: Screen Size
Okay so I am very very slowly working on my projector (15.4 Polaroid LCDTV) and I want to DIY a 120" screen or a 100" screen so either way I go what are the vertical and horizontal dimensions.
A 120" diagonal 16:9 screen is 105" wide and 59" tall.
A 120" diagonal 4:3 screen is 96" wide and 72" tall.
A 100" diagonal 16:9 screen is 87" wide and 49" tall.
A 100" diagonal 4:3 screen is 80" wide and 60" tall.
I have found the easiest way to work with this is to decide how wide the screen will be then multiply by 16 and divide by 9.
A 120" diagonal 4:3 screen is 96" wide and 72" tall.
A 100" diagonal 16:9 screen is 87" wide and 49" tall.
A 100" diagonal 4:3 screen is 80" wide and 60" tall.
I have found the easiest way to work with this is to decide how wide the screen will be then multiply by 16 and divide by 9.
Great thanks for all the answers 
I work with angles all the time (work realted Trusses for homes) but usually they are 45 degrees or 90 degrees basically 4:4 screen or 16:16 screen and I couldnt warp my head around the 4:3 and 16:9 ratios 
So I guess the BO cloth will not work for the 120 or 100 I think its only 45" I could be wrong though I hope I am.
oops sorry its actually 54"
I work with angles all the time (work realted Trusses for homes) but usually they are 45 degrees or 90 degrees basically 4:4 screen or 16:16 screen and I couldnt warp my head around the 4:3 and 16:9 ratios oops sorry its actually 54"
Keep in mind that the BOC is 54" wide but by the time you wrap it around the frame and staple it to the back, you could lose 2" to 3" per edge. So worst case you would have 48" on the face of the screen and that translates into a 98" diagonal 16:9 screen size. For a 4:3 that only results in a screen 64" wide. That is an 80" diagonal 4:3 screen.
I have found the formulas on this page to be quite helpful (original credit to Death Ray J for finding these)
QUOTE
How to Calculate a Custom Screen Size
Use the following formulas to calculate a custom size. The formulas will assist you in finding the viewing area only.
HDTV (1.78)
Video Format
Diagonal x 0.49091 = Height
Diagonal x 0.87247 = Width
Height x 2.0395 = Diagonal
Width x 1.14585 = Diagonal
Height x 1.78 = Width
Width x 0.561837 = Height
NTSC (1.33)
Video Format
Diagonal/1.667 = Height
Height x 1.33 = Width
Width/1.33 = Height
Height x 1.667 = Diagonal
Use the following formulas to calculate a custom size. The formulas will assist you in finding the viewing area only.
HDTV (1.78)
Video Format
Diagonal x 0.49091 = Height
Diagonal x 0.87247 = Width
Height x 2.0395 = Diagonal
Width x 1.14585 = Diagonal
Height x 1.78 = Width
Width x 0.561837 = Height
NTSC (1.33)
Video Format
Diagonal/1.667 = Height
Height x 1.33 = Width
Width/1.33 = Height
Height x 1.667 = Diagonal
I have found the best way to do it is to build the projector and set it up where you want it. Then measure the actual projection size and build your screen to that size. Some of the lcds aren't perfectly 4:3 or 16:9 aspect ratio.
Here is my little "cheat sheet".
it's a zipped .xls file, just enter in yellow boxes and it calcs HxW.
pixel (ie. ratio dimensions are unitless)
HxW units are whatever you input for Diagonal.
Click to view attachment
it's a zipped .xls file, just enter in yellow boxes and it calcs HxW.
pixel (ie. ratio dimensions are unitless)
HxW units are whatever you input for Diagonal.
Click to view attachment
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