8mm Forum: 16mm projector lens.

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Topic: 16mm projector lens.

Tassos Laudas
Expert Film Handler

Posts: 102
From: Viersen Germany
Registered: Mar 2006

posted May 05, 2007 07:18 PM

I've recently been given an 1,3 35/65mm Xenon lens, made by ISCO Germany, for my Bauer p8 that carries the original 1,3 35/65mm lens already. As i haven't found the ideal conditions to make comparisons yet i am wondering which one is supposed to be better? Is the Xenon one supposed to provide more light? If yes, would this be at the expense of sharpnes or the opposite? I am really curious

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted May 07, 2007 04:10 PM

It sounds as if they're both the same. The speed (1.3) refers to how "fast" the lens is (and f/stop is a mathmatical computation a T/stop is a measured amount and may differ from an f/stop). Sound as if the difference is probably the engraving, BUT the only real test for any lens is putting a picture up on the screen with a good test chart. Lens in the same manfacturing lot will be different. Cinematographer have their favorite lenses and request them by serial number from Panavision when ordering a camera package for a feature.

A theatre may try several lenses to a find a matched pair, although with platters this is less the case than in the past with first run houses.

In short, test the lens, make sure the room is dark, the film is good and the projector is at a right angle to the screen and without keystone.

Check them thru the entire zoom range and you may find one sharper at one point than the other lens.

John

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Tassos Laudas
Expert Film Handler

Posts: 102
From: Viersen Germany
Registered: Mar 2006

posted May 07, 2007 05:10 PM

John i really appreciate your answering. I simply thought that "xenon" meant superior quality compared with non xenon lenses. Anyway i did test the two and found out that the xenon one gives a relatively yellow picture although somewhat brighter while the other one provides a white and rather sharper one! There certainly is some difference!

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted May 08, 2007 09:17 AM

Tassos,
Well it look like the "Xenon" marking on the lens has to do with it's color quality since the xenon light source has a might higher/bluer light, the lens is balanced for that. Your order lens is balanced for a tungsten lamp which has a lower color temperature source.
Xenon = 5000-6000 degress K (bluish, like daylight)
Tungsten = 3400-3500 degress K (yellow-red like indoor lamps)

John

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