Film-Tech Forum ARCHIVE: 1.85:1 aspet ratio lens

This is topic 1.85:1 aspet ratio lens in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mike McFarland (Member # 7765) on 10-25-2019, 03:04 PM:

Is a special lens required for projecting movies in the 1.85:1 aspect ratio? I thought it was done by cropping the print itself. Someone has one for sale on Ebay. Thanks

Posted by Marcel Birgelen (Member # 6801) on 10-25-2019, 06:22 PM:

A standard spherical lens works for the 1.85 AR, commonly known as "flat".

But a little more information would be welcome. What kind of projector are we talking about? And you've never shown a movie in 1.85 before?

Posted by Paul Finn (Member # 10726) on 10-26-2019, 08:18 AM:

The aspect ratio of the picture, 1.85:1 here, is "cropped" with the correct size aperture plate in the projector gate system hardware. The lens "focal length" is chosen to size the cropped picture to fit the dimensions of the movie screen. Spherical projection lenses are not aspect ratio specific and are only related in the film source picture vs. screen size picture requirements.

Paul Finn

Posted by Carsten Kurz (Member # 5396) on 10-26-2019, 01:39 PM:

They may sometimes refer to these lenses as '1.85' or 'flat' if that lens has actually been used in a cinema for flat. Also, maybe they do also sell the scope base lens and/or anamorphic, and then just try to discern both offers.

- Carsten

Posted by Carsten Kurz (Member # 5396) on 10-26-2019, 05:21 PM:

Hmm, looks as if there are many ISCO lenses sold on ebay that carry '1.85' in their name (even engraved on the lens barrel). So, I guess that is what the thread opener refers to?

https://www.ebay.com/itm/ISCO-45mm-545324-ULTRA-STAR-HD-PLUS-1-85-MC-2-4-LENS-1955/162695718589?hash=item25e16ba6bd:g:p2oAAOSw3YNXZOpE

Posted by Randy Stankey (Member # 64) on 10-26-2019, 06:03 PM:

I used to mark my lenses for their aspect ratios using a paint marker. I had a lens for 2.39 AR and one for 1.85 AR but I also had one for 1.66 AR because we showed a lot of foreign movies.

Personally, I just knew which lens was which because I installed them but one can never count on anybody else who runs the machine to know one lens from another without marking them.

Lenses are chosen for each projector based on the design of the theater. (Screen size, throw, aspect, etc.) Each lens is custom installed into each projector and a matching aperture plate is created for each installation. When everything is said and done there will be a matched set of lens and aperture plate for each projector and for each aspect ratio that the operator wants to present.

There isn't such a thing as a "1.85 lens," per se. A lens used to project 1.85 AR on one projector might not work on another projector.

Yes, I can understand why somebody would say one lens is a "1.85 lens" and another is a "2.39 lens" but, in truth, a lens is a lens as long as anamorphics aren't involved.

Posted by Mike McFarland (Member # 7765) on 10-28-2019, 06:16 PM:

Thanks to everyone for the replies! What you are saying is pretty much what I thought. I've just never seen a lens marked 1.85:1 before. It's probably just a way to distinguish between flat and anamorphic since most movies were either 1.85:1 or 2.35:1. Here is the link to the Ebay item if anyone is interested.

https://www.ebay.com/itm/35mm-movie-projector-Lens-Simplex-Century-Film-Aluminum-body-with-1-85-LENS/133175110293?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

Posted by Randy Stankey (Member # 64) on 10-29-2019, 01:13 AM:

It looks like the marking, " RIGHT 1.85" is a label that somebody stuck on.

Apparently, it's a salvaged lens from a dual projector setup. Whoever ran that booth marked their lenses like I used to, only they had a label printer.

It's obvious that the person selling the lens (and the lens adapter collar) doesn't understand what they have.

The one piece of critical information that you need isn't shown... The focal length. Without the focal length you have no way to know whether the lens is right for your projection system.

None of the pictures in that auction show the part of the lens where the focal length and other specs would be engraved.

It also looks like either a piece of the lens is missing or else somebody else has added an extension collar to make the lens fit inside the adapter ring. I can't tell from the pictures.

Although the price of the goods isn't too bad, I can't recommend a purchase with confidence until we know more.

At minimum, you'll need to know the focal length.

Best if you knew the model and serial numbers. That way you could look up the exact specs of the lens from the manufacturer and know, with certainty, whether the lens is what you need.

Posted by Marcel Birgelen (Member # 6801) on 10-29-2019, 02:36 AM:

The "collar" doesn't look standard to me either. Maybe it was put on to fit into a "lens revolver"?

Anyway, I think that this collar is hiding the engraving of the lens that would list the focal length, type number and serial number.

Like Andy indicated, without at least the focal length, you're nowhere.

Posted by Timothy Eiler (Member # 383) on 10-29-2019, 08:45 AM:

quote: Marcel Birgelen
The "collar" doesn't look standard to me either. Maybe it was put on to fit into a "lens revolver"?

That looks like the lens collar i used to see in simplex projectors

Posted by Randy Stankey (Member # 64) on 10-29-2019, 09:19 AM:

The collar on some older Simplex projectors sometimes has an alignment ring.

It's used as a depth stop so that you don't have to fuss around with focus each time you remove and install the lens.

There is also a pin that mates with a slot on the front of the projector to align your amamorphic lens. Again, reduces the need for fussing when you change lenses. Your focus and alignment will always be spot on.

If you have a projector that doesn't have a lens changer those rings come in handy when you need to change lenses.

Posted by Martin Brooks (Member # 1269) on 10-29-2019, 09:50 PM:

FW=DA where:
F=focal length of the lens in inches
W=Width of the screen in feet (for 1.85 projection)
D= Distance from the screen in feet
A=Aperture, which for 1.85 is ideally .825"

F=DA/W, W=DA/F, D=FW/A, A=FW/D