If you are talking about the actual
barrel, you can easily tell by the length.
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Credit to BillESC:
Here are the minimum lengths of the
Altman fixtures with
lens completely retracted.
6 X 9 - 16 1/2"
6 X 12 - 20 1/8"
6 X 16 - 21"
6 X 22 - 29"
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However, it is more difficult to tell the difference between
lens tubes, which is what I think you're trying to do.
Is that what you're trying to do? (The
lens tube is the part that holds the
gel frame).
An easy way I've found to do this is to remove every tube from every light. Then grab a
360Q (let's say a 6x9), hang it from a pipe or put it on a
base, bring it up to a moderate
intensity, and slide each tube in and put aside the ones that give a good focus. You then know that those are 6x9 tubes. Then take a 6x12
instrument and repeat the process. This will be more of a process of elimination, and hopefully nobody has mixed lenses within a single tube.
Another (and more tedious) way to tell them apart is to pull the front
lens out and measure it.
A 6x9
lens will be about 1 1/4" thick and a 6x12
lens will be about 7/8" thick. To accurately measure a
lens, set it belly-side down on a table. Then just measure from the table to the
flat side of the
lens.
Unfortunately I don't have any 6x16 or 6x22 lenses to measure, but I believe the 6x22 uses a single
lens (should be the same
lens as a 6x16) so that should be easy. Any
lens tubes left over *must* be a 6x16 (in a perfect world
).
Some
Altman 360Q units I've seen have the designation written on the outside of the tube in permanent marker. If your instruments have this, you're in luck. If not, it wouldn't be a bad idea to do this when you find out what they are.
*This might be a good time to do a
lens cleaning party. Those
360Q's aren't the brightest, but they will surprise you when they have good, clean lenses!