The diameter of the lens has nothing to do with the size of the lcd. You need a large diameter lens normally because the combination of your fresnels and objective enlarge the arc image especially with the 450mm objective lens and 550mm fresnel.
do the math: 550/220=2.5 x 33mm arc length= 82.5mm
The other thing you need to be concerned about is the Field of View of your objective lens. This has nothing to do with Focal length. Because it has a 360mm does not necessarily mean it wont see a 17 inch diagnol lcd. It means it needs to have a wider FOV then a longer lens like the pro lens but it can still work if it has wide enough FOV.
Since its a process lens it should be fine up to 20 inch lcd.
The shorter Focal lenght helps me in 2 ways.
1. The arc image is not magnified as much since i dont need to use 550 fresnel. It means I dont need a 82.5 mm diameter projection lens.
2. Gives me a large image on the screen at short distance which is what i want.
do the math: 550/220=2.5 x 33mm arc length= 82.5mm
The other thing you need to be concerned about is the Field of View of your objective lens. This has nothing to do with Focal length. Because it has a 360mm does not necessarily mean it wont see a 17 inch diagnol lcd. It means it needs to have a wider FOV then a longer lens like the pro lens but it can still work if it has wide enough FOV.
Since its a process lens it should be fine up to 20 inch lcd.
The shorter Focal lenght helps me in 2 ways.
1. The arc image is not magnified as much since i dont need to use 550 fresnel. It means I dont need a 82.5 mm diameter projection lens.
2. Gives me a large image on the screen at short distance which is what i want.
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