Help needed choosing lenses!

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Hi,
Im really confused on what lenses I should by. I ve read that I should use tripplet objective lens but I ve got no idea on what size (mm) I should buy! I am planning to use a 4:3 HAMI 8" inches screen.

Can someone please advise me about the type, made of lenses and optics generally I should buy.

Also any online shops are really welcome (I already know FIY company and lumenlab).

I ve already read far too many threads but I m still confused! Any advise?

Athan
 
for the hami i would go for 24cm focal or less.

tell us your throw and your desired diagonal size so you can work out the lens focal. Then just find the closest lens for that focal.

1/focal=1/lcd-triplet distance + 1/throw distance

trhow dist / lcdtriplet dist = magnification

imagesize diagonal / hami diagonal = magnification

do you like maths? 😀
 
Hi Rox,
thanks for your answer!
Well I m ok with maths, but not with terminology!
Could you just explain throw, and desired diagonal size. If you with the second you mean the size of the screen, then I suppose that something like 100 inches would be ... really good 😀
lcd-triplet distance? Where can I get this info from?
 
ok, thats what you should do;

desired diagonal projected image: 100"

hami is 8" diag so 100/8=12,5 magnificaion is what you need.

lcd-lens (lcd--triplet) distance lets call it "D", and throw is the distance from lens to the wall, lets say "T".

the relation T/D=needs to be 12,5 since it is the magnification you would like to have. So we can say T=D*12,5

now lets see what happens if you had 240mm focal triplet;

1/240 = 1/D + 1/T
1/240 = 1/D + 1/D*12,5

you can work out D=259,2mm. So you need to place the projection lens at 259,2mm from the lcd to have your 100" image with 12,5*D=12,5*259,2=3,24meters throw. If you find your trhow being to much long, then you need a shorter focal lens.
 
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