8mm Forum: My first experience with SCOPE (not good)

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Posted by Winbert Hutahaean (Member # 58) on September 13, 2007, 03:48 AM:

Hi there,

Again, this is about my new comming soon theatre.

As my previous post has told you my aim to have a biggest picture possible.

I finally has turned the ST 1200 on and found the 150w light was bright enough for my small theatre.

I set the projector lens to the biggest possible. At a flat film, the projction is OK.

But when the scope film was presented with a 16mm anamorphic lens, the problem appears.

I did a test with "Neverending Story" (Derann 600 feet Scope).

I couldn't make the picture at maximum zoom (the biggest picture) since the projected picture will be rounding, instead of square (16:9) picture. I think the rounding picture came from the edge of anamorphic lens.

I still could get a square pictrue, but I have to set the projector lens to the smallest zoom and my aim to have a big picture was not reached.

I, then, changed the anamorphic lens with the bigger one (dedicated for 35 mm projector). It has a bigger lens and heavy also. It helped a bit, and I could get a bit bigger scope picture. But it's still not to the maximum that my Elmo projector could do. Because if I set to the maximum, a rounding picture would still appear.

I don't have a bracket yet, so I use my hand to hold the anamorphic for a tes. Therefor, infact, the distance between the Projector lens and the anamorphic lens is 0 cm.

Why the rounding picture happened?

I don't know what would happen if I use a bracket, since ther should be a distance between the 2 lens?

thanks,

Posted by Joerg Polzfusz (Member # 602) on September 13, 2007, 04:40 AM:

Hi,

this "rounding" is normally called "vignetting". It's mainly caused by the length and the front diameter of the anamorphic lens. Take a look at "Figure 8" on this webpage: http://www.vanwalree.com/optics/vignetting.html
Your anamorphic lens blocks the light like the hood used for this drawing.

Jörg

Posted by Winbert Hutahaean (Member # 58) on September 13, 2007, 05:16 AM:

Joerg,

Thanks for the reply. Perhaps that is the one in correct term.

So when I set the projector lens to the biggest picture it will not show a full square. So how to avoid this but I can still get the biggest picture?

thanks,

[ October 22, 2009, 10:47 AM: Message edited by: Winbert Hutahaean ]

Posted by Lee Mannering (Member # 728) on September 13, 2007, 05:19 AM:

Winbert
I wonder what lens your Elmo has in it?
When I started with Scope in the 70's I had trouble with lenses also. Try and get the lens as close to your projector lens as you can this may help. In the end I un screwed the projector lens front and used to project with the Scope lens up against the projector lens front. This all but solved the problem and also the fact that I was only a young lad with no money to buy a better scope and projector lens.

Many of the projector lenses have lens front elements that are deeply recessed which does not help anamorphic projection with supplementary lenses sad to say.

Today, and years later I use the Kowa 8Z lens with a Eumig F1.2 in a Stereo machine and I have no problems.

Hope my early experience is of help.

Posted by David Kilderry (Member # 549) on September 13, 2007, 05:37 AM:

Hi Winbert,

I have an ST 1200 and run scope without any vignetting. I have a few different Kowa anamorphic lenses and they are all OK on various focal lengths of the zoom lens in the Elmo.

How far is your throw (screen to projector lens distance)? Perhaps it is too short?

David

Posted by Barry Johnson (Member # 84) on September 13, 2007, 07:16 AM:

No.I dont get any vignetting on my ST1200 or any of my St8 projectors.
Your attachment is too far away from the projector lens or,as already intoned,the anamorph has a very deep hood.
Remember,the further away from the projection lens will increase the airspace between the attachment and thus will give you this unfortunate picture.No amount of zooming in or out will get rid of it until the attachments is dead on.

Posted by John Clancy (Member # 49) on September 13, 2007, 11:08 AM:

I had exactly this problem when I started out into the world of 'Scope. I too was using a 16mm 'Scope lens and it just wasn't suited to the short throw we tend to use with Super 8.

As others have said, the Kowa 8Z should be the solution. I think I can zoom up full with my 14 foot throw and still not get any vignetting. I use the Elmo F1.0 lenses.

Posted by Gary Crawford (Member # 67) on September 13, 2007, 11:34 AM:

Can't speak for the Kowa 8z, but I use a kowa 16D and haven't had any trouble with it. I don't have to zoom out all the way , though. But I filled a 17 foot screen with it and no trouble. Have to butt that scope lens right up against the prime lens. Steve Osbourne of Reel Images sells a scope lens that appears to have a very wide diameter that would seem to cover the picture even fully zoomed out.

Posted by Jean-Marc Toussaint (Member # 270) on September 13, 2007, 01:26 PM:

The best scope lens I've projected with on super 8 and 16 mm machines (Elmos) is the Elmoscope II, aka Kowa 8Z, because of its bigger rear end element. John is right, you can almost go all the way to the shorter end (12.5 or 15 mm) without vigneting.
It's so good that it's being used on Keith Wilton's 35mm projector (I use an Isco on mine, though).

Posted by Winbert Hutahaean (Member # 58) on September 14, 2007, 12:16 AM:

Sorry for all my bad terms, due to my ignorance on technology. I can only use very layman words.

This is what I have:

1. The projector lens is the original for Elmo ST-1200 (I guess 1.3)
2. The scope lenses are no brand for 16mm and Sankor for 35mmm. Both lenses showed vignetting.
3. The distance between projector lens and scope lens is 0 cm becuase I don't have a bracket yet and therefore using my hand for holding the scope lens.
4. The distance between the projector to the screen is approx. 3 meter (eqv. 9 feet)

Anything wrong to the above spec?

thanks,

Posted by Kevin Clark (Member # 211) on September 14, 2007, 02:01 AM:

Hello Winbert.
The distance between the projector and screen cannot cause vignetting, the problem is simply the 'scope lenses you have are not suitable for the largest image produced by the Elmo 1.3 zoom lens. The 16mm scope lens is likely too narrow in diameter. With the 35mm lens it is likely the diameter will be OK but the longer physical length of the lens menas the projected picture 'hits' the inside of the front end of the 'scope lens barrel causing vignetting again.
Solution: either use the Elmo zoom lens and set it to produce a smaller picture in the first place, or sell your current 'scope lenses on here or Ebay and buy a Kowa 8Z or Kowa 16H - I've used both of these with all sorts of Elmo & Beaulieu Super 8 projector combinations for many years with no problems at all. Other 'scope lenses may be cheaper but you only need to buy one good Kowa 8Z or 16H and you will be sorted. Also remember not all Kowa lens models are the same - go for a 8Z or 16H or you may end up with a Kowa lens made for 16mm and experience vignetting yet again!
Hope this helps.
Kevin

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