8mm Forum: Lens question :)!!!

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Topic: Lens question :)!!!

Elyas Tesfaye
Jedi Master Film Handler

Posts: 520
From: Winnipeg, Manitoba, Canada
Registered: Nov 2012

posted February 27, 2016 08:29 AM

Hi all,

what would "zoom convertor 16- 0.75 ~ 1.25x" mean [Smile]

? Thanks

!!!

Cheers,
Elyas

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted February 27, 2016 08:43 AM

A zoom converter screws into a basic lens and alters its focal length. This is achieved by rotating its front element.
The figures indicate its ratio range of plus or minus 25%, i.e., with the standard 2" lens it will give a range from 1.75" to 2.25".

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Maurice

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Elyas Tesfaye
Jedi Master Film Handler

Posts: 520
From: Winnipeg, Manitoba, Canada
Registered: Nov 2012

posted February 27, 2016 09:14 AM

Hi Maurice,

thanks a lot and can you please dumb it down for me, as I'm not that familiar with lenses... Lay man's terms, please [Smile]

!!! Like, for example, this lens is a good short/ long throw lens [Big Grin]

...

Cheers,
Elyas

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Elyas Tesfaye
Jedi Master Film Handler

Posts: 520
From: Winnipeg, Manitoba, Canada
Registered: Nov 2012

posted February 27, 2016 02:04 PM

Hi Maurice,

I should give myself more credit, I actually totally understand what you mean n thanks again [Smile]

!!!

Cheers,
Elyas

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Elyas Tesfaye
Jedi Master Film Handler

Posts: 520
From: Winnipeg, Manitoba, Canada
Registered: Nov 2012

posted February 27, 2016 05:44 PM

Follow up question, this would affect the f/... tho, right? N if so, by how much [Smile]

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Paul Mason
Jedi Master Film Handler

Posts: 540
From: Aldershot, Hampshire, UK
Registered: Nov 2013

posted February 29, 2016 04:05 AM

Hi Elyas,
Zoom converters for projectors do not change the marked F number significantly because they are mounted on the front. For example F1.4 stays at F1.4. Any actual change due to losses in the extra glass will be unnoticeable.

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Paul.

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Elyas Tesfaye
Jedi Master Film Handler

Posts: 520
From: Winnipeg, Manitoba, Canada
Registered: Nov 2012

posted March 02, 2016 09:15 PM

Hi Paul,

thank you so much [Smile]

!!!

Best,
Elyas

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Dino Everette
Phenomenal Film Handler

Posts: 1535
From: Long Beach, CA USA
Registered: Dec 2008

posted March 22, 2016 01:01 AM

quote:
For example F1.4 stays at F1.4. Any actual change due to losses in the extra glass will be unnoticeable

This is not entirely true since the sheer act of enlarging the picture across the screen will actually cause the amount of light to change so, while the actual numerical F-stop won't be different, what it represents (which is the light output) will, so your f 1.4 will be more like an f1.6 at 1.25x

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"You're too Far Out Miss Lawrence"

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Elyas Tesfaye
Jedi Master Film Handler

Posts: 520
From: Winnipeg, Manitoba, Canada
Registered: Nov 2012

posted March 22, 2016 05:14 PM

Hi Dino,

thanks a ton for the heads up, you sir, are awesome [Smile]

!!!

Best,
ET

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Dino Everette
Phenomenal Film Handler

Posts: 1535
From: Long Beach, CA USA
Registered: Dec 2008

posted March 22, 2016 10:52 PM

Elyas - the easiest way to look at lenses is to think LESS IS MORE

so with "f" - the lower the number, the more light that comes through basically working your way towards an f 1.0

BUT sometimes in order to push more light through there is a sacrifice in sharpness, so an averaged priced lens at f1.2 might be easier to focus in razor sharp than a similarly priced f 1.0

same thing with "inches" or "mm" - a 1 inch or 25mm lens is going to throw a much larger picture in a shorter distance than a 50mm or 2 inch lens, but often at the cost of both the sharpness and the light output, so while your 2 inch lens might be an f1.2, there is a very good chance your 1 inch lens will be more like f1.6 and there is a very good chance you will also have a harder time focusing in you 1 inch f1.6 than you would your f1.2....

This is the main reason why most projectors come with a standard 2 inch lens, which is usually around f1.2 or f1.3

I have multiple lenses for each of the projectors I use regularly because depending on the circumstances sometimes I need to throw a big picture in a short distance, and other times I have a longer throw....Basically the goal is to fill whatever screen you are using so it looks as nice, clean and professional as possible.

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"You're too Far Out Miss Lawrence"

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Elyas Tesfaye
Jedi Master Film Handler

Posts: 520
From: Winnipeg, Manitoba, Canada
Registered: Nov 2012

posted March 23, 2016 02:19 AM

Hi Dino,

thanks a ton for the heads up, you sir, are awesome [Smile]

!!!

Best,
ET

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