I saw other peoples boxes, but how do you exactly fiure out the best dimensions of the box you're going to build? I have the pro kit, 17" LCD- but thinking about it a 1080p projector is still very expensive, so I would like to be able to upgrade the monitor later to a 22"- if at all possible(22" is the only common 1080p monitor I know of).

The calculator on here I found shows some things, but how do I figure out the distance from the triplet to the first fresnel(and which one is which), fresnel to LCD, LCD to next fresnel, distance to light from last fresnel.

I want to start building the box but I don't know for certain how to figure out the dimensions! Also, would it be wise to not cut the fresnels and hope to eventually upgrade to a 22", or is there another way to go?


Also- why build a light box, and is it required? Safety, or for better use of the light?

Since the light produces UV - I had read that most builds use lexan to keep the UV from reaching the fresnel and LCDs- is this needed even with good ventilation, and what is best to use that won't absorb much of the light?

johnzo1995 sells a 15.4 that does 1080p i think that 22 will be toooo big

So you think it will be better to build it to do max 17" - and then upgrade to the 15" at 1080p? How much about is the 1080p 15"?

I think I've seen it before, but had thought that it was a laptop screen and controller

Yes the 15.4 is a laptop LCD, with a custom controller. Its width is 13 5/8" X 8 3/4" or close to that these are total outside measurements. So if you make a 15"er and make it 14 5/8" wide (inside measurements) you will be able to place one of them into it later on.

From the ? you have asked I would recommend that you read the projector guides and learn to use the focal calc. All will give you measurements for starting placements of parts. You need to make a test bed for test placement so your measurements will be exact.

A light box is not needed as long as you place a heat shield like flashing around your light source. Most light boxes are made to enhance light and to direct it towards the LCD.

The calc you mentioned is more than likely the focal calc and it gives you the distance to the LCD to the triplet which is more accurate for better focus then doing it from the field fresnel. the smaller 20mm # is used for light processing to get the most out of the lcd and it can be changed to your likes.

UV is only problem in areas were light is visible. lexan will take care of most of it. There are some who use UV filter glass or lexan and those who don't. It is your choice this is DIY if you are worried about it then use what you feel is needed to protect you or your family. The light coming out of your triplet has gone through one triplet, 2 fresnel, 2 polarizers and the LCD You do the math. Venting has nothing to do with UV radiation it is use to vent IR, light not used converts to heat, Heat is what you vent out of your PJ





Luck on your PJ

Joe


Fresnel FL can be found by placing both side by side with something behind them when you look at them setup this way the one that is magified the most is the shorter focal lenth

Yeah, it still doesn't make any sense- everything is based off of 15" screeens, and can't find enough info on building a simple box for a 17" screen. I don't understand how the focal calculator gives any measurements besides obvious ones, and the distance from LCD to triplet.

How do I find the distance from triplet to LCD to next triplet? How do I find distance from light to triplet? From all that I have found so far it's basically "build it long".... and I haven't found anyone with a 17" and the pro lenses that showed their dimensions used.


How can I find dimensions? I've been through the guides and cant find any help in this regard

Um, what? No offense, but I think you need to read up a bit before you even think about cutting some wood. No idea what you mean by "next triplet" but there is only one triplet -- the projection lens. I think you are confusing a couple things.

Here's how to determine the minimum length of your box, assuming no folds (mirrors) are employed:

1. Your rear fresnel's focal length will determine the maximum distance between it and your lamp arc. I say maximum because this can be shortened somewhat using a precondenser lens but that might complexify things too much for you. So, say for example, you are using a 220mm FL rear fresnel (pretty much the standard). That means that fresnel should be placed 220mm from your lamp arc.

2. Your triplet/projection lens's focal length will determine the distance between the LCD (the object it is focusing on) and the lens itself. For this, you need to use Dazzla's focal calculator. Plugging in the numbers will give you an approximate LCD to lens distance, based on your desired throw and/or screen size.

3. If you add the results of #1 and #2, factor in an additional 20mm between rear fresnel and front fresnel (in an unsplit) or LCD (split), and another 20mm between front fresnel and LCD (unsplit) or LCD and front fresnel (split), and toss in whatever your light engine will require, you will then know the approximate length of your box.

4. Width and height are determined mostly by LCD size. You obviously need at least the minimum dimensions of the LCD, plus whatever extra needed to mount it and the fresnels, etc.

Sorry, I had said triplet but had been talking about the fresnel. I know there is only one triplet, that I got pretty quickly

Thank you for the help! That makes everything much clearer now.

One other thing I haven't understood is what split vs. unsplit is. From what I understand, the light path goes light--> rear fresnel (which would be the 220mm- and found because it magnifies things less than the 650mm) ->LCD -> front fresnel - > triplet -> wall.

Does it matter if there is the 650mm fresnel in front of the LCD for "Dazzla's focal calculator", or is the front fresnel ignored for this?

Thank you for the help, cleared up alot of confusion I've been looking for information for for awhile.

Split means the LCD is between the fresnels. Unsplit means both fresnels are behind the LCD (between it and the lamp). The latter is generally thought of as the better way to go, as anything between the LCD and the lens decreases the overall quality of the projection. However, if you need to keystone (angle the projector), then you have to use a split setup (unless you want to lens shift, which is another ball of wax).

You can choose split or unsplit for Dazzla's calculator. It changes the LCD to lens and throw figures a bit.

This is all spelled out rather well in the wiki. You really should read it at least a dozen times or so, until it all sinks in.

Gotta jump in here and say thanks heaps for that explanation of the dimensions of the box... that plus using Dazzla's focal calculator has made me much more confident with planning my dimensions (I figure a bit of extra room front and back is ok to begin with too for room to move).

One question I would have though (which may make things a little trickier) is I plan to use (at least to start with) two lenses from an OHP as my projection lense (I assume this is equivalent to a doublet?) am I correct in thinking the best way to do this would be to put the rear lense in a fixed location and make the front lense moveable so that it can be shortened or lengthened... and would this effectively give me a little option for throw/screen size adjustment?

But again thanks for a great explanation of box dimensions!

Afraid I can't be of help with the doublet, as I have no experience with them. Sounds like it may over-complexify things. Triplets are pretty cheap -- I recommend getting one instead of worrying about multiple lens adjustments.

Thanks for the info... I suspect once I get money I probably will track down a nice triplet... I'm just using this lens set up for the moment to reduce cost... the light source is actually the main cost at the moment... once that is sorted then I can move onto triplet consideration

Your not reading answers correctly I told you that the fresnel that was magnified larger would be the 220mm.


You need to read this over and over until you understand it http://www.lumenlab.com/protectedwiki/


And thumb through topics here http://www.lumenlab.com/forums/index.php?showforum=17


If you are interested in a folded 17" go here http://www.lumenlab.com/forums/index.php?showtopic=2581


If a straight shooter is what you want then reply 9 will help you here http://www.lumenlab.com/forums/index.php?showtopic=8007


Dude you just need to read instead of writing down every thought you have,