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Author Topic: Aperture Gobo Effective?  (Read 552 times)

Brian Garrett

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Aperture Gobo Effective?
« on: March 30, 2017, 10:39:08 am »

I have several Chauvet Intimdator LED moving heads.  I wonder if an aperture gobo (small hole gobo) would effectively make beams like this pic?  I know that's not how the yellow beams in the rig below are accomplished on such a big scale, but at a bar gig, could it have a similar effect? 


Could a gobo like this maybe do that on a small scale? 
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TJ (Tom) Cornish

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Re: Aperture Gobo Effective?
« Reply #1 on: March 30, 2017, 10:56:13 am »

I have several Chauvet Intimdator LED moving heads.  I wonder if an aperture gobo (small hole gobo) would effectively make beams like this pic?  I know that's not how the yellow beams in the rig below are accomplished on such a big scale, but at a bar gig, could it have a similar effect? 


Could a gobo like this maybe do that on a small scale? 

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Brian Garrett

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Re: Aperture Gobo Effective?
« Reply #2 on: March 30, 2017, 11:01:24 am »

Thanks to the welcome wagon...
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TJ (Tom) Cornish

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Re: Aperture Gobo Effective?
« Reply #3 on: March 30, 2017, 11:52:58 am »

I have several Chauvet Intimdator LED moving heads.  I wonder if an aperture gobo (small hole gobo) would effectively make beams like this pic?  I know that's not how the yellow beams in the rig below are accomplished on such a big scale, but at a bar gig, could it have a similar effect? 


Could a gobo like this maybe do that on a small scale? 

Brian, it will sort of do what you want.  Beam fixtures use optics that concentrate all the light into the beam.  This device is like a fixed iris, which narrows the output of the fixture, but the beam will be the same brightness as the inner part of the original beam; not benefiting from the concentrated output of a real beam fixture.  In other words, it will be narrower and dimmer than it was before, but may still be usable.

As an example, here's a demo video of a moving light fixture that has a variable iris option.

https://www.youtube.com/watch?v=QsLFNeJdXYQ

The iris demo happens at about 1:40.

BTW, welcome to the forum.
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Brian Garrett

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Re: Aperture Gobo Effective?
« Reply #4 on: March 30, 2017, 01:20:07 pm »

That's a perfect example.  Thank you. 

I knew that I'd lose the brightness associated with the light that hits the back side of the gobo, but wondered how the lens would impact the remaining beam.  I may swap out a gobo for the resulting effect. 

I clicked through the youtube vid to a clay paky demo where it looked as if it used multiple lenses to tighten to beam, not just an aperture.  I assumed the upscale, pro gear used an optic approach to such a powerful, tight beam. 

Thanks for the response. 
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Jeff Lelko

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Re: Aperture Gobo Effective?
« Reply #5 on: March 30, 2017, 08:37:24 pm »

...but wondered how the lens would impact the remaining beam...

The lens won't impact the remaining beam any differently than any other gobo would, or using no gobo at all.  While dropping a small circular gobo or tight iris into a light has been referred to as a poor man's beam effect here and elsewhere on several occasions, that's really not quite accurate.  TJ explained this well, but to put it in other words, a gobo or iris doesn't change the beam angle of a light - it only masks part of the light to achieve the desired look.  Think of it as a subtractive effect.  A zoom lens on the other hand slides a lens down a set of shafts and/or worm gears to physically change the optical properties of the light path.  You lose no percentage of the light's output as you zoom in, though as you zoom out the resulting beam will be dimmer because you're covering more area.  The same principle applies to a "beam" light, just that some are fixed at a very tight beam angle...others can zoom a bit.  Zooming lights and legitimate beam lights generally are more expensive because these lenses and zoom assemblies cost more to make than a simple gobo or iris.  It's just a matter of what you're willing to pay for it!  Hope this helps!
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Brian Garrett

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Re: Aperture Gobo Effective?
« Reply #6 on: April 20, 2017, 10:20:29 am »

I get the science of optics and beam angles, etc.  I wondered what the experience was.  I initially started looking for concave lenses that were about the required thickness, but at best I get large versions of that diameter-wise and expensive.  I'd have to somehow cut them down to diameter.  The gobo in my lights are allowed to be 1.1mm, but the engineer in me sees way more room, especially if I glued the lens into the holder/gear.  I assume I could use the full thickness of the gear that way. 

The thought was the concave lens would tighten the beam as it headed towards the standard lens, giving it a different incident angle resulting in tighter overall beam but without using the power of the LED.  It looks like an undertaking. 

I ordered some gobos with an aperture. They do alright, but as you guys say the angle is still obvious.  Like I said, as an amateur I'm dealing with 25W LEDs and a upstage truss height of about 10', so I'm not going to get the exact awesomeness as in the pics, but the aperture did not result in a tight beam, it is still very much a cone of light.  That's not what I'm going for. 

Thanks for the input. 
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Jeff Lelko

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Re: Aperture Gobo Effective?
« Reply #7 on: April 20, 2017, 07:43:15 pm »

I get the science of optics and beam angles, etc. 
...
but the aperture did not result in a tight beam, it is still very much a cone of light.  That's not what I'm going for. 

If the first half of this statement is true, I'm not sure why you seem surprised by the result.  I don't mean to come off sounding blunt, but let me repeat myself:

...to put it in other words, a gobo or iris doesn't change the beam angle of a light - it only masks part of the light to achieve the desired look.  Think of it as a subtractive effect. 

That's pretty much it - you're not going to do any better with a gobo alone. 

I initially started looking for concave lenses that were about the required thickness, but at best I get large versions of that diameter-wise and expensive.  I'd have to somehow cut them down to diameter.  The gobo in my lights are allowed to be 1.1mm, but the engineer in me sees way more room, especially if I glued the lens into the holder/gear.  I assume I could use the full thickness of the gear that way. 

The thought was the concave lens would tighten the beam as it headed towards the standard lens, giving it a different incident angle resulting in tighter overall beam but without using the power of the LED.  It looks like an undertaking. 

I don't think this would really work as intended either, and even if it did, I wouldn't recommend trying it.  It's one thing to shoehorn a fixture into an application that it wasn't intended for - it's a whole other thing to intentionally modify a fixture DIY-style or insert products that aren't intended to be used with the fixture.  Aside from voiding warranties (which I suspect you already know), you can run into all sorts of other issues with the unit too.  Insurance also tends to frown on equipment with mods that are against the manufacturer's recommendation.  I don't mean to rain on your parade, but there's a reason why authentic Sharpys cost real money. 

I get that being an amateur means having to work within a very tight budget, but with the low cost of Chinese fixtures on ebay I have to think you can find something with the desired "beam" effect for not that much money.  It'll almost certainly be better and cheaper in the long run compared to modifying your existing fixtures.  Hope this helps!
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Brian Garrett

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Re: Aperture Gobo Effective?
« Reply #8 on: May 08, 2017, 10:28:11 am »

If the first half of this statement is true, I'm not sure why you seem surprised by the result.  I don't mean to come off sounding blunt, but let me repeat myself:

That's pretty much it - you're not going to do any better with a gobo alone. 

I don't think this would really work as intended either, and even if it did, I wouldn't recommend trying it.  It's one thing to shoehorn a fixture into an application that it wasn't intended for - it's a whole other thing to intentionally modify a fixture DIY-style or insert products that aren't intended to be used with the fixture.  Aside from voiding warranties (which I suspect you already know), you can run into all sorts of other issues with the unit too.  Insurance also tends to frown on equipment with mods that are against the manufacturer's recommendation.  I don't mean to rain on your parade, but there's a reason why authentic Sharpys cost real money. 

I get that being an amateur means having to work within a very tight budget, but with the low cost of Chinese fixtures on ebay I have to think you can find something with the desired "beam" effect for not that much money.  It'll almost certainly be better and cheaper in the long run compared to modifying your existing fixtures.  Hope this helps!


You're not raining on any parade, though it seems you're definitely trying to take shots at a newbie.  I'm having a great time playing with my gear and experimenting.  I look forward to learning from almost anyone. 
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duane massey

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Re: Aperture Gobo Effective?
« Reply #9 on: May 09, 2017, 12:06:14 am »

Gobos are cheap. Try it. If you're using rotating gobos, try an offset beam, as you can get a very cool effect rotating the beam. Used to do this with Technobeams back in "the day"..
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Duane Massey
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Brian Garrett

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Re: Aperture Gobo Effective?
« Reply #10 on: May 09, 2017, 09:20:05 am »

Gobos are cheap. Try it. If you're using rotating gobos, try an offset beam, as you can get a very cool effect rotating the beam. Used to do this with Technobeams back in "the day"..


I grabbed an aperture gobo and it's useful. 

I thought a lot about the offset beams or even a 3 dot kind of thing to give a pretty cool effect.  I'll probably pick some of those up. 

Thanks for the input!
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