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Iscorama 54 not working as it should.


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#1 Adam Paul

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Posted 27 December 2006 - 08:37 AM

I finally got a hold on an Iscorama 54 lens after looking for one for a long time. But I?m getting some weird results with it though. First, I always heard that one of the positive features with the Iscorama was it?s focus system. You just needed to set the focus on your lens to infinity and use the Iscorama focus ring to do the focusing. But with my lens it?s working the other way around. I need to set the Iscorama to infinity and use my lens focus ring to do the focusing. It won?t work any other way. Besides that I can?t always focus. I had a subject about 4 meters away from the front element and I couldn?t bring it into focus. That was at a 100mm focal length. Since the lens has a MOD of 1.25m at 100mm FL and the Isco is supposed to focus at 2 meters I don?t understand why it wouldn?t focus.
Now something I found interesting. The Isco?s back element is convex. Shouldn?t the front element be convex instead? The front element is flat. I?m sure this is right, but all anamorphic lenses I know have a convex front element.
By the way, does it matter how close the back element on the Isco is to the front element of the lens? Thanks in advance.
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#2 Leo Anthony Vale

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Posted 27 December 2006 - 03:52 PM

I finally got a hold on an Iscorama 54 lens after looking for one for a long time. But I?m getting some weird results with it though. First, I always heard that one of the positive features with the Iscorama was it?s focus system. You just needed to set the focus on your lens to infinity and use the Iscorama focus ring to do the focusing. But with my lens it?s working the other way around. I need to set the Iscorama to infinity and use my lens focus ring to do the focusing. It won?t work any other way. Besides that I can?t always focus. I had a subject about 4 meters away from the front element and I couldn?t bring it into focus. That was at a 100mm focal length. Since the lens has a MOD of 1.25m at 100mm FL and the Isco is supposed to focus at 2 meters I don?t understand why it wouldn?t focus.
Now something I found interesting. The Isco?s back element is convex. Shouldn?t the front element be convex instead? The front element is flat. I?m sure this is right, but all anamorphic lenses I know have a convex front element.
By the way, does it matter how close the back element on the Isco is to the front element of the lens? Thanks in advance.


Is your backing lens focusing properly? Collimnated? That could be a problem.
Or the Iscorama helical is off.

The front elements of the Iscorama is the spherical focusing system, something like a variable close up diopter. At infinity the spherical elements ought to be touching and have zero power, effectively being an optical flat. So it makes sense that the front would be flat.

The closer the better.
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#3 Adam Paul

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Posted 27 December 2006 - 04:23 PM

Is your backing lens focusing properly? Collimnated? That could be a problem.
Or the Iscorama helical is off.


What do you mean by helical?

The front elements of the Iscorama is the spherical focusing system, something like a variable close up diopter. At infinity the spherical elements ought to be touching and have zero power, effectively being an optical flat. So it makes sense that the front would be flat.


So it seems the back being convex is the right thing.
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#4 Adam Paul

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Posted 28 December 2006 - 11:42 AM

This place used to be packed with Super-8 experts and now all I get is one single opinion?What happened?
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#5 Leo Anthony Vale

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Posted 29 December 2006 - 12:31 PM

What do you mean by helical?
So it seems the back being convex is the right thing.


The helical is the focusing thread. I've been told the helical on the Iscorama sometimes seizes, but you said yours still moves.

Is it spherical convex or cylindrical convex?

Anyway, in a basic anamorphotic attachment the front group is negative and the rear group is positive.
Usually the front element is cylindrical concave and the rear element is cylindrical convex.

The Iscorama has a spherical focusing section added to the front, thus the front element of the system is not
cylindrical.
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#6 Adam Paul

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Posted 29 December 2006 - 12:50 PM

The helical is the focusing thread. I've been told the helical on the Iscorama sometimes seizes, but you said yours still moves.


Yes, my focus ring spins fine and smooth.

Is it spherical convex or cylindrical convex?


Not sure. Hard to see. It's built in and all I can see is the convex end.

Anyway, in a basic anamorphotic attachment the front group is negative and the rear group is positive.
Usually the front element is cylindrical concave and the rear element is cylindrical convex.
The Iscorama has a spherical focusing section added to the front, thus the front element of the system is not
cylindrical.


Yes, the front is just flat.
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