8mm Forum: Question about lenses (This whole 'f' & 'inch' lingo).

This is topic Question about lenses (This whole 'f' & 'inch' lingo). in forum 16mm Forum at 8mm Forum.

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Posted by Elyas Tesfaye (Member # 3356) on April 08, 2013, 03:57 PM:

Hi all,

hoping y'all had a great weekend, my question is if 'f' and 'inch' mean the same thing in lens lingo :/? Trying to figure out what they mean, for starters, and if they are the same thing... Tried googling them but couldn't find a comprehensible (well, to me, at least lol) answer [Frown]

... Thanks again, as always, for your help [Smile]

!!!

Best,
ET

Posted by David Ollerearnshaw (Member # 3296) on April 08, 2013, 05:24 PM:

I could be totally wrong, but you never know.
For my ELMO super 8 projector I have the original lens a F1.3 then I bought the F1.0 I also have the long throw lens at f1.4 (I think) The lower F lets more light through, but focusing is more critical.

The Long throw is 25mm to 50mm which means you can still fill your screen further away and not have too larger image that spills over. In imperial 1" to 2" The larger the lens the further away you can project from and still get the same size screen.

I bought the long throw for when I used to go to the local old folks home every month to give a show for them. the GS1200 gave a good image of 72" with this lens at about 50ft length room.

It should be the same for 16mm On my 16mm set-up I have a B&H converter the makes the image larger and just fills my screen. 16mm lenes always seem to be non zoom.

Posted by Jeff Missinne (Member # 3373) on April 08, 2013, 06:09 PM:

Here's a link to a chart showing what to expect in terms of image sizes with different lenses at various distances:

http://www.insightlighting.co.uk/HIRE/hire%20pdfs/16mm%20throw-1.pdf

Most 16mm projectors came with a 2-inch lens as standard equipment. Other lenses were usually sold as accessories, and can be hard to find for some models. Bell & Howell's zoom lens, called the Filmovara, screwed into the front of the regular lens; Kalart Victor and some others preferred an all-in-one unit that would replace the regular lens.

Posted by Elyas Tesfaye (Member # 3356) on April 09, 2013, 03:29 AM:

Thanks a ton, Dave n Jeff [Smile]

...

I just ordered a 1 inch lens so I'm hoping with the microscopic room I have (3.5 meters throw length) I should get a decent sized screen out of my Kodak Pageant AV 126... Thanks for the chart Jeff, lemme see what I can find [Smile]

...

Best,
ET

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