For the most part all the pics I see is of massive 7' screens etc...

That is way to big for me. I want something like 50" diagnol.

Can the 1005 Lumenlab Lens Kit achieve this?
I ask because some projectors have a minimum screen size where any thing below that they are blurry.

So what is the range for the DiY LL projector?

How close does hte projector have to be to get a 40" - 60" diagnol image?

thanks!

The original triplet has a 1:1 ratio.
Meaning that in order to have a 10' screen it has to be 10' away.
For what you want the projector has to be 40" to 60" away, but I'm not sure if it can focus that close.


peace

If you need to go that small, then your best option is probably to build a rear projection TV, but it is still in development. Have you looked at the RPTV section in the advanced builder forums yet?

Here's a link.

You could also achieve this by using the standard lens kit, but a smaller LCD, like the 7" lilliput.

Hmmm... Yeah that might be more what he's looking for.

Thanks Fly.

so whats the minimum screen size that it can display nice and sharp?

Why would it be possible with the lilliput and not the regular 15" design?

Smaller screen, smaller projection. A more pertinate question might be "How close to the wall do you want it before you can't move it out of your way?"

You can get a 60" screen with a 7" panel at 10' away from the wall.

Check out the Lumenlab focal lenghth calculator.

With the 15" panel you would have to be only 5'3" away from the wall for a 60" projection. Too close because you would have to angle it up or down too much to keep it out of your way. Unless you want to sit only 5 or 6' from the screen.

If you want a smaller screen with the higher resolution of a 15" panel, you will need the pro lens or build an RPTV.

what about if he used one of the longer focal length "bad" fresnels. longer focal length would give a smaller image

I think that would just affect the light fill of the lens, not the screen size.

The triplet is still focusing on the panel. I might be wrong, I'm still learning about these optics too.

No, deathray's got it right. The FL of the field fresnel in no way affects the FL of the projection lens. The field lens only exists to collect horizontal light and angle it toward the pj lens.

why is it then when i move the fresnel closer to the triplet that my image gets bigger?

same reason that keystoning works

So whats the smalled screen that can be achieved with th regular lens, while still being completely focused and sharp?

Is there a minimum?

For example if I put it 4 ft from the screen, will my image be blurry or can it be focused?

(forget about if it is in my way or anything like that for the moment, just want to know if it can focus at those small distances)

thanks

has anyone tried placing another lens in front of the triplet to change the FL and add throw?

so is it possible to have a focused 60" diagonal image from a 17" LCD setup with a pro lens and at 7' feet away from the screen?

http://lumenlab.com/focal_calc.php

Im after the same info, I have a reasonably small room, I am going to ceiling mount, with an estimated 60" - 70" screen, will the image be able to focus and be clear from the projector

(The projector will be close to the wall, but out of my field of view, will be hanging almost right above me)

You look like are gona have the same setup as me.

My projector will be 60 to 70 inches away from my screen, and I will be right under it too. Thus it will be hanging on the celling. Are you building a 15" one or 17"??? I really want the 1280x1024 resolution to play games on it but box will be huge (almost 1 meter long) and will be exactly 65"inches from the screen.

Brains, let me get this right so I know am using the calculator right:

1. Size of object to be projected in inches = Size of LCD I am using in my projector (15", or 17", or 19")

2. Distance from projector lens to screen in inches = Distance from the Center of the Triplet Lens to the projected screen (Black out)

3. Size of projected image in inches = Size of the Projected Image on the Blackout

4. Focal length of lens in inches = Now I get confused here, Focal length of which lens??? The Triplet?? or the First Freshnal or 2nd Freshnal????????


Did I get the frist 3 right??? Thanx!!!!!

I will be using a 15" most likely the BenQ FP567 Version2 1024 x 768 450:1 16ms

Just measured out my wall, the absolute maximum size screen I can fit would be 87" , and there is enough room for the projector to create that image too, although I may go a bit smaller than that (probably 80") so its not taking up the whole wall.

Actually, A vertical projector may be the way to go for me, mount it on the back wall (solid brick)

Right on all points. You'd only fill in 3 variables and let the calc compute the fourth. The focal length is for the projection lens. 25.4mm = 1" so a 320mm lens would be 12.6". If you leave the screen size blank and fill in the panel, pj lens and throw distance, the calc will compute the screen size for you.

I actually get confused by this too and I'm not sure my #s are correct because I'm not sure which dimension should be entered for the sizes. Do I enter the diagonal screen size (ie 15") or the width or the height? Is the screen size returned the diagonal or the width (I've seen posts where either was assumed so it is clear as mud)...Although it shouldn't make a huge difference I guess, is the screen to lens distance determined based on a straight on center line projection to the center of the screen?

Ah the joys of newbie confusion!

What you get out is what you put in. So, if you enter the diagonal dimension for the "Size of object to be projected in inches (ie. your LCD panel):", then you will get the diagonal dimension out of "Size of projected image in inches:", if you enter the horizontal dimension, you will get out the horizontal dimension...

Unless Im completely missing something, I dont think anyone has answered our question, whether A 50-70" screen can bu focus properly. I dont need to calculate screen size, I just want to know whether or not it can be focused at that size.
I only ask because I have a retail projector that wouldnt focus below 40" and the image would be blurry and completely unwatchable.

You can focus it at that size. Your projection lens will be farther out from the panel than normal.

Cheers