I'm using a Slusher box and I'm going to modify it for the Pro lens.

All I'm going to do is make a longer and wider focus box, but here's my question.

How wide should I make the focus box so that I don't lose the light coming into the Pro lens ?

My current focus box is 6"*6" and 5 1/2" long. My new focus box is going to have to be 12" long. But if I leave it 6"*6" square it will be to long and narrow to allow the light through.

So what should it be ? Will 8"*8" be enough or should it be bigger?

Thanks guys.

I used the focal calc to determine the size needed. You could do a scale drawing like this pic and just try the different sized extensions. 100mm adjustment may be a bit extreme but I wanted to cover as many throw distances as possible. Just a note, the pro triplet faces the opposite way compared to the standard triplet, mounting flange is at the rear of the lens. I forgot to write down the actual distance but by memory I think it was 570mm to the centre of the triplet for a 120” screen using a 17” LCD.

DJ

I don't think you understood what I was saying. I know how far the Pro lens needs to be from the Lcd. What I need to know is this.

If I have a 12" long focus box, what width and height should I make it so that ligh isn't blocked from entering it ?

Like if it is 6"wide and 6" tall and 12" long will the light be blocked as it comes down that long of a "tunnel"

Does it need to be 10"tall and 10" wide . Keep in mind that it HAS to be 12" long to get the proper distance since I'm using an existing box which is to short.

What, you want me to do the maths for you?
Hmm.. Ok I suppose I’ll do it. :angry:
What is the smallest screen you would like to display?
What is your LCD size?

DJ

Man this is harder than I thought to explain. I know what size screen to display, I know how far apart to put everything. I just want to make sure I don't lose the light going to the triplet.

You know how people use a shower drain as a focus for the standard lens ? But if the drain is not cut off, if they leave it to long, it blocks the light !

Now my focus box is 12" LONG !!!! Not your standard average length. So let's say that the focus box was only wide enough to fit the lens, say 4-5" square. There is NO WAY that the light would hit the lens. The sides of the focus box would cut it off. SO WITH A FOCUS BOX 12" LONG WHAT SIZE SHOULD I MAKE IT SO I DON"T GET THE LIGHT CUT OFF ON THE EDGES...

Crappy pic to follow:

Dazzzla,

Okay... you have me worried here... I think I will have to rebuild my focus box because of the flipped triplet... I don't have the lenses, but should in a few days... Take a look at my Cone Drawing... It is for a 90" Diagonal w/ Unsplit Fresnels... I have a 20mm Air Gap between the fresnels and LCD... The Fresnels are ~40mm wider than the LCD to compensate for the convergence angle... extra light will be masked by the LCD Frame... my concern from the beginning was the fact that such a small cone was hitting the triplet... Do all the measurements look correct? I used your calculator for this... What do you think?

T

Ahhhh Nevermind......

I'm going to go ahead with a different design.

Dazzzla gave you the answer and you don't even have to do any math just put a 12" focus box over the drawing provided and see if the lines cross and you will know if a 12" is beig enough or not.

Click to view attachment

Also make sure that yo account for a minimum +/- 1" focus, with the focal length being double you might need to double the adjustment as well so +/- 2" wouldn't be a bad idea.

Pagercam - take a look at my post / drawing above... does this look right?

I resopnded in the other thread. No it isn't right, we need to focus the triplet (500mm FL) the fresnels are juts gathering the light for the triplet so base the measurements on the triplet length not the fresnels and adjust to "fill" the triplet

So the lens is mounted with it sticking out of the box.

Guess that's why when I flipped it around I got a better focus.

Well here's what I did instead of a 12" long focus box :

Cool.... How is the focus and projected image?

The focus is perfect corner to corner and the projected image is around 115" diagonal with the projector about 20' back.

The image seems to be about 5-10% brighter than it was with the standard lens. Of course this is after fresnel adjustments.

Oh and I'm still using the 330mm/220mm fresnels until I build a frame for the new Pro fresnels. So I have the image 1:1 ratio at 720p which keeps it in the center of the scre en away from any dark corners.

So are you saying that you have moved the arc very close to the 220mm fresnel so that the light enters the triplet? That’s a long stretch for those poor little fresnels.

DJ

Well the Lcd is the same distance from the light as it was in the standard setup. I'm using an unsplit fresnel arrangement and the fresnels are about 3" behind the LCD instead of 1/2" - 1" behind the Lcd. And the Pro Lens is the required 500mm or so from the Lcd.

nice job on the focus extension, heres what I did. dont have to worry about the light cone getting clipped off!

That was my other guess

I’m getting really frustrated here. All I want to do is finish my box but I can’t because it’s so bloody hot here to work. :angry: It’s now 1.45AM and only just cooled down to a more sane condition. Might be a bit too late to start up the tools though.

DJ

Hey Daz,

I'll trade you for the nine inches of snow we got here yesterday!

Done deal. Now what time does that flight depart?
I don’t mind that hot weather in moderation but it has been reeeeaaaally hot here for the last couple of weeks, I think it’s starting to ware me down.