8mm Forum: Optical and magnetic

This is topic Optical and magnetic in forum 8mm Forum at 8mm Forum.

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Posted by John Almond (Member # 1782) on December 26, 2009, 05:08 PM:

Could some kind soul explain the diff, and the avantages from one to the other.
And just another Q, at what distance from the screen would you get a 90" by 90" picture from an elmo 1200 (yes you might have read somwhere that I am getting the said machine) and would like to fill my indoor screen as much has possible.
Regards.
John

Posted by Gian Luca Mario Loncrini (Member # 1417) on December 26, 2009, 05:12 PM:

John, take a look at this old thread:

Optical or magnetic sound?

Cheers.
GIAN

Posted by John Almond (Member # 1782) on December 26, 2009, 05:18 PM:

Cheers GIAN
Regards,
John

Posted by Gian Luca Mario Loncrini (Member # 1417) on December 26, 2009, 05:19 PM:

More than welcome [Wink]

Posted by John Almond (Member # 1782) on December 26, 2009, 05:23 PM:

Any idea of the distance Q?

Posted by Claus Harding (Member # 702) on December 26, 2009, 11:27 PM:

John,

Using the standard 1.3 15-25mm lens at the widest lens setting, you need about 21 feet of throw. I put my 1200 up to double-check it, and that is as close as you can get and still get the 90 inches across.
(If you splurge and get a 1.1 lens, the focal length starts at 12.5mm on that one, so you can be a bit closer and have more light on the screen.)

Claus.

Posted by John Almond (Member # 1782) on December 27, 2009, 06:12 AM:

Thank you Claus. ummmmm wonder how much for one of thoses lenses? and where from ?????????. Mind you if I have the projector at 21 feet that would mean the projector would be in the dining room and we have double doors between there and the living room so I will have to run a speaker from the projector to the screen. Yip, Ive just measured the distance from screen to 21 feet and I am 5 feet from the dining room window.
How to post photos on here is the next puzzle.

Posted by Gian Luca Mario Loncrini (Member # 1417) on December 27, 2009, 06:44 AM:

Sorry I did not reply the second question of your post, John (but I can see someone else did [Big Grin]

).

Just because the metric system it's not the same here, of course.

Posted by Winbert Hutahaean (Member # 58) on December 27, 2009, 09:27 AM:

Gian (and others)

IF you have difficulty in (any) conversion, use this website: http://www.wolframalpha.com/.

This can basically convert, calculate, explain, etc almost anything. Jst type on the box any numbers/symbol (e.g. 12" or you can also write 12 inches). And it will show the related results.

John, because flat print will always has 3:4 comparison so your 90" (width) will have 67.5" height. Or if you have 90" (height) the width will be 120". I am using this formula:

quote:
3 : 4 = 90 : x

quote:
3 : 4 = x : 90
----> 4x = (90 x 3)
----> x = 270 : 4
----> x = 67.5
(if you have 90" as the width)

You need a very long throw between projector and screen to achieve that size.

For others, wasn't there a short throw lens sold? Can it fit to Elmo 1200?

thanks

Posted by Claus Harding (Member # 702) on December 27, 2009, 11:20 AM:

John,

The 1.1 lenses come up from time to time, on the forum and on EBay. I have seen them for $125-150 sometimes, but I don't know what the 'accepted' price is considered these days.

They are faster in terms of light let through, and they have better optical quality than the 1.3 (less fringing or 'chromatic aberration' as it is called.)

Because they have shallow depth of field, focusing has to be right on, and your projector should be dead level to the screen for best results.

For uploading pictures, here's what I do:

Once I have the shots I want, I run them through photo editing software (many free ones available) and re-size the pictures so they are 550 pixels in width, which is the maximum allowed on our site.
Then I save them together in a group on my desktop, with a name that indicates they are the smaller size for net use.

When you want to post here, click below the box you write messages in, where it says "Click here to upload an image"

At the bottom of the 'upload' page, put your name and your forum password, then hit "browse" to find the picture on your desktop.

Click on the pic, then hit "submit".

If all is well, you get a page showing your chosen pic along with an acknowledgement that you have done it right.

You then "copy" the whole data thread above the picture, and "paste" it into your message, and this should happen:

Try it sometime, just as a test, to see how it works for you.

Claus.

Posted by John Almond (Member # 1782) on December 27, 2009, 01:22 PM:

Heres a shot of my screen.........Its 106" from corner to corner (approx), thats a 32" tv next to it.
And thanks for the instructions

[ December 27, 2009, 03:10 PM: Message edited by: John Almond ]

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