quote: Brandon Lokesak

---

however when i have just the bulb running and no film in i can get rid of the shadows by turning the focus knob it makes the bulb area so crisp but when the film is threaded the film is way out of focus. Any Ideas here?

---

your are focusing the aperture when you do that. The edges of the plate become sharp in focus. That is why you are out of focus for the film.

Check your bulb focus spread using the scope lens. Make sure the light is evenly spread accross the screen.
 

---

Posted by Peter Mork (Member # 1336) on 06-24-2004, 03:47 PM:
 
Anothe thought - is there a screw-on tube at the front of the lens that might be blocking some of the light? This has been known to happen. Replace any tube with a shorter one and see if it makes a difference.
 

---

Posted by Paul G. Thompson (Member # 655) on 06-24-2004, 06:19 PM:
 
Could this be vignetting due to optical centerline of the lens being mis-aligned (especially with an extremely short focal point lens?) Is there a chance the project beam is being clipped as it goes out the porthole? Is is possible that the aperature place is screwed up.

I agree - time to run some alignment test film. There is umpteen things that can cause the problem.
 

---

Posted by Brandon Lokesak (Member # 2280) on 06-24-2004, 07:23 PM:
 
When I filed the apature i took only a little bit off and u could see a faint line from the soundbar but the shadow was still there so i dont think that it is the apature plate. The image isnt being clipped off by the port window to my knowledge because u can still see the picture its not really completely black its just a shadow in a way. I got one theatre pretty close but not perfect by moving the lens back in the lens mount a bit but that doesnt make any sense to me because thats just focusing it with out turning the knob. Thanks for all the help im getting this time around.
 

---

Posted by Paul G. Thompson (Member # 655) on 06-24-2004, 10:03 PM:
 
What is the throw and lens size?

Kill the xenon lamp, wait about 5 seconds or so and look down the barrel. You might see something.

How much area does the projected light cover on the final element of the lens?

What kind of projector, and what kind of xenon?
 

---

Posted by Gordon McLeod (Member # 33) on 06-24-2004, 10:49 PM:
 
Take the apperture out and see if the shadow is gone if it is then it is the culprit and its edges will have to be delt with
If it is still there then it is something else
 

---

Posted by Mike Pennell (Member # 1692) on 06-24-2004, 10:50 PM:
 
Its possible it might be the actual gate thats causing the shadow. Pull out the aperture with a white screen and see if the shadow is still there. If it is remove the gate/trap and see if its still there. If it isnt, for some reason ive seen the light clip the metal of the hole that leads to the aperture itself.
 

---

Posted by Dominic Espinosa (Member # 2122) on 06-25-2004, 03:26 AM:
 
It's obvious, but I figure it oughta be pointed out anyway...
Whenever you're diddling with your bulb with no film in the gate make sure to close your dowser every 30 seconds or so so as not to crack the lens. It's not a pretty picture. (Pun intended.)
 

---

Posted by Mitchell Dvoskin (Member # 751) on 06-25-2004, 07:49 AM:
 
Working with a lot of small screening rooms, I frequently see this problem with short focal length lenses, specifically under 2.75" lenes. The problem is caused by the lens being so far back toward the gate that it picks up the little bit of ambiant light that is visable around the aperture plate cutout. If the film was right up against the plate, this would not happen, but that can not be, otherwise the plate would scratch the film. I Never did find a solution for this, other than bringing in the masking a little to cover it.

/Mitchell
 

---

Posted by Gordon McLeod (Member # 33) on 06-25-2004, 09:32 AM:
 
That is one of the advantages of the small lens that Zeis placed directly behind the apperture was to convert the cone of light into parrallel light. It matched the projection lens and greatly improved sharpness and contrast and light transmision
Meo still uses them on their projectors
 

---

Posted by Christos Mitsakis (Member # 143) on 06-26-2004, 11:32 AM:
 
Brandon,
Have you checked if the working distance of the mirror to the film gate it is to lamphouse specs? Also is it a vertical or horizontal lamphouse?

C.
 

---

Posted by Christos Mitsakis (Member # 143) on 06-26-2004, 11:32 AM:
 
oops mistake.
C.
 

---

Posted by Ron Keillor (Member # 1790) on 06-26-2004, 08:46 PM:
 
It would be useful to know the width of the shadow on the screen.
At Oakridge there is a distinct lack of reflectivity on one side of the screen in theatre 3 when showing 'Scope which matches the width of the masking when brought out for 'flat' pictures, as if the surface might have been abraded or there have been a chemical interaction between the masking material and the screen surface.
 

---

Posted by Brandon Lokesak (Member # 2280) on 06-27-2004, 03:55 PM:
 
Its a horizontal bulb and we have no side masking to masking to cover it up. The only thing I stumbled across was by moving the lens in or out a little bit and refocusing the film it made the shadow smaller it was about 6 inches before now its about 3 but its still annoying as all hell. I wish i could find the manual for the lamphouse to know the measurements from mirror to gate but we dont have the manuals. When putting a lens in the lens holder is there a special way to align it or focus it should the focus knob be in the middle then focus the lens by moving it by hand in and out? Thanks for all the help guys I appreciate it.
 

---

Posted by Gordon McLeod (Member # 33) on 06-27-2004, 04:13 PM:
 
The problem is most like the fact that on an SA the apperture plate is well behind he film bands.So it will be a soft edge the odd part is the topand bottom edges are not affected.
Anyway did you try pulling the plate and seeing if the problem went away?

The lamphouse manual is on line here as you probably have the cinemecanica zenith3000H (the 2000H is the same)
the workin distance is shown on one of the drawings from various points of the lamphouse body depending on the nose cone provided
 

---

Posted by Thomas Procyk (Member # 1170) on 06-27-2004, 04:37 PM:
 
SAY! I've got a GREAT IDEA that would solve this problem FOR SURE!

Brandon and everyone should go back to the old thread, which I have conveniently placed a link to here, and re-read these parts:

The omnipetent Brad Miller begins:

quote:

---

Although this is probably not his problem, it could be that his screens have fixed masking at 2:1 and the lamp was tightly focused down on the scope format, creating dark sides on flat films.

---

quote: Brandon Lokesak

---

We have no side masking

---

quote:

---

do you have any top or bottom masking???

---

quote:

---

In responce to the top and bottom masking question there is no masking.

---

quote:

---

it sounds like the picture is as good as it's going to be unless you get movable masking. with a shorter lens you could fill the screen side-to-side, but you'd be cropping the top/bottom (some people might prefer that alternative). there's a good chance you're cropping the sides of your scope image as well. what are the dimensions of the visible screen?

---

quote:

---

The dark sides for flat were indeed caused by the apeture plate, but it was cut propery for flat. It was caused by -- surprise -- too wide of a screen with no masking.

---

quote:

---

I know I posted this before but i never really got an answer and I messed around alittle bit more and got some new results...I filed the plate but they are still there however...

---

quote: Brandon Lokesak

---

When I filed the apature i took only a little bit off and u could see a faint line from the soundbar...

---

So even though there has been discussion regarding his screen dimensions and the possibility of it being a fixed 2:1 screen, he has not answered that all-important question, and we still have the silly bastard taking apart his lamphouse, whipping out test films he doesn't have and re-aligning mirrors.

My guess? It's a 2:1 screen. Crop, or live with the bars. Or get masking like a REAL theater.

Jinkies, I think I've solved the mystery! ZOINKS!

=TMP=
 

---

Posted by Sam Hunter (Member # 1119) on 06-27-2004, 04:47 PM:
 
I think you need to lay off the drugs there TP

Instead of being the smart ass you are Thomas and trying to show everybody how great your film tech enspired ego is why don't you offer some suggestions that may help the guy or better yet shut the hell up. So what if he doesn't do things right, or in the right order, doesn't mean he wont learn from his mistakes. He came to Film Tech for help and you should be tolerant of his actions and do your best to give help or at least shut up and let the reel experts help.

Take your pick of the following:


[ 06-27-2004, 08:38 PM: Message edited by: Sam Hunter ]
 

---

Posted by Gordon McLeod (Member # 33) on 06-27-2004, 04:59 PM:
 
You may be on to something but If some one says dark band I would not consider unlit white screen dark but just that grey white unused area not a dark band from a shadow but still the question is if one removes the apperture does the band move?
 

---

Posted by Greg Mueller (Member # 17) on 06-28-2004, 09:08 PM:
 
Brandon
I tried to email you but I guess my email privileges have been suspended. Drop me a line will you?

(Admin edit - no they have not. Read the FAQ for your answer and policy regarding this.)

[ 06-29-2004, 01:16 PM: Message edited by: Brad Miller ]
 

---

Posted by Thomas Procyk (Member # 1170) on 06-29-2004, 12:35 PM:
 
Sam, I will not entertain your rude comments here. If you had read the end of my post, or the previous thread, you would have seen that I DID give the suggestion I was blatantly, albeit sarcastically making reference to.

You must have been really bored between those four hours from when you initially posted, to when you added that whole other paragraph below the to have so elloquently fashioned your insults.

I'll take my pick of all of the above, package them up nicely, dust it with some powdered sugar, tie a bow around it, and send it back your way, you overflowing mound of quivering love-pudding!

So, Brandon, have you measured that screen yet? Only trying to help...

=TMP=
 

---

Posted by Brad Miller (Member # 2) on 06-29-2004, 01:28 PM:
 
If any member has a problem with another member's posts, email me.

quote: Sam Hunter

---

I think you need to lay off the drugs there TP

Instead of being the smart ass you are Thomas and trying to show everybody how great your film tech enspired ego is why don't you offer some suggestions that may help the guy or better yet shut the hell up. So what if he doesn't do things right, or in the right order, doesn't mean he wont learn from his mistakes. He came to Film Tech for help and you should be tolerant of his actions and do your best to give help or at least shut up and let the reel experts help.

---