Conventional Fixtures Telling Altman 3.5Q Lenses Apart

hobbsies

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Jan 13, 2010
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San Diego
Hi guys,

I have some altman 3.5Q with two different lenses and I'm trying to figure out which lens tube is which degree.

Anyone play with these and can tell which is which? I THINK the one of the left is 38° and the one on the right is 28° but I just want confirmation.
 

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Van

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CB Mods
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360Q-6X12_zpsc82a7dd6.jpg



TADA!
 

hobbsies

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Jan 13, 2010
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San Diego
There's complicated reasons why I can't just turn them on and measure the beams. Also those are 360 Qs, although I have the data sheets for 3.5Qs. I was hoping to be able to tell by lens configuration which was which.
 

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MRW Lights

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Jan 4, 2017
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NYC
Well it's more complicated than lenses in this case I'm afraid. Altman Ellipsoidals use a combination of lenses and barrel lengths on the body of the unit, it's possible to have the wrong lens train in a body and throw off your photometrics all together. With it off it's only kind of a best guess... one of the best effects on a show I was working came from someone leaving the lens tube out of a unit and when it turned on during focus we kept it in the show and used it without a lens because it looked great.
 

RonHebbard

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There's complicated reasons why I can't just turn them on and measure the beams. Also those are 360 Qs, although I have the data sheets for 3.5Qs. I was hoping to be able to tell by lens configuration which was which.
Just thinking out loud here but how about this: Pull the lens tubes out of the fixtures. Leave the tubes assembled (keep the individual lenses in the tubes) Hold the lens tubes one at a time over a flat surface and measure the relative heights at which they focus. When I've done this, I've usually been in a space with tubular fluorescents overhead and it was easy to place a sheet of paper on a work bench and make reference marks of the fluorescents when they were in focus. This wouldn't give me precise information but was definitely a quick and easy way of comparing the various focal lengths and sorting them into matching groups.
Toodleoo!
Ron Hebbard.
 
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hobbsies

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Jan 13, 2010
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San Diego
Altman Ellipsoidals use a combination of lenses and barrel lengths on the body of the unit, it's possible to have the wrong lens train in a body and throw off your photometrics all together.
I know that's true of the 360Q's, but is that also the case with the 3.5's as well? I'll have to take a closer look at the bodies I have and make sure they're the same.


Just thinking out loud here but how about this: Pull the lens tubes out of the fixtures. Leave the tubes assembled (keep the individual lenses in the tubes) Hold the lens tubes one at a time over a flat surface and measure the relative heights at which they focus. When I've done this, I've usually been in a space with tubular fluorescents overhead and it was easy to place a sheet of paper on a work bench and make reference marks of the fluorescents when they were in focus. This wouldn't give me precise information but was definitely a quick and easy way of comparing the various focal lengths and sorting them into matching groups.
This is an interesting idea. Thanks for the suggestion.

There's two reasons I can't turn em on - firstly is that the union isn't on call for a few more hours, and second these fixtures don't have connectors on them. Our contract is complicated enough that there's some things I can do without them present (like take inventory) and others I need a union head on call to do (like do maintenance/turn lights on).
 

theatricalmatt

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May 25, 2013
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New England
Place the lens housing on a flat surface, like a tech table or desk. Mark the edge of the lens (right in front of the gel frame holder) with a piece of spike tape. Use a Maglite or flashlight app on your phone to replicate the lamp that would be in the housing. Place a clipboard in front of the lens and shift until it comes to its sharpest focus. Spike that in a different color. Measure the distance. If you've got an app on your phone for it, enter in the distance + resultant beam spread and determine the field and beam angle.

Repeat for different lenses, spiking the clipboard with a different color when you find a different lens. Altman 3.5s came in, iirc, five different barrels (3.5 x 5, x6, x8, x10, x12). After a while you can sort out oddballs, like the ones that won't focus at any length, which probably means they have a lens flipped around or the wrong lens inserted.

As an added bonus, put a piece of spike tape on the lens tube to indicate its angle, and you'll never have to do this again. ;) (or, mark in Sharpie / paint pen.)
 

venuetech

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Apr 14, 2008
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AK,
Use a paint pen. I would mask the frame ears and color code them with spray paint. ( easy to ID from a distance)
 

ship

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Mar 29, 2003
Location
Illinois
Lenses are about 0.52 times their focal length radai of curvature. (Important information for everyone to write into their perminant notes.)

Fixture Lens Conversion Guide:
50̊ - 3.5Q5 / 360Q-4.5x6.5 (45̊)
40̊ - 3.5Q6 / 360Q-6x9 (37̊)
30̊ - 3.5Q8 / 360Q-6x12 (27̊)
20̊ - 3.5Q10 / 360Q-6x16 (17̊)
10̊ / 12̊ - 3.5Q12 / 360Q-6x22 (9.5̊)
5̊ - None
8x8 (20̊)
8x10 (16̊)
8x16 (6̊)

How you establish radius of curvature... should be easy enough but I have no idea of how other than a molding template maker and some drafting. (Above notes were written into my "Backstage Handbook" as notes from books read many years before I started citing the sources for the information. Possible source is McCandless as an author for one I think three books read.)

Also, a note that I have seen many table top heights of say a 6x9 lens. Believe I remember something like 1.1/8"-7/8" in convex side towards the table measuring the flat side of lenses height. I have always tried to match lenses to each other for height, and after that focusing the lens would fix that. Between lens spacers I have never noted different heights of which would be the only otherwise factor - in how close the lens train lenses are spread from each other. This lens spacer height even between brands is seemingly similar.

Match the lenses in table height and you have at least a basis for a starting point. If you know you don't have any 3.5Q12 or 3.5Q10 in stock from the inventory, you should only have three sizes of lenses once stood on a table convex side down - choices.

I own some 3.5Q5 and 3.5Q6 fixtures, if of help, I can measure that table height.

Otherwise, "Jet Dry" filled in its well of your dish washer in a normal hot wash, or commercial dish washers are the best way to clean them once removed and if not dichroic. Might as well clean them once removed.
 
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