Focusing Source Four LED Ellipsoidals

Smatticus

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Jan 2, 2004
Location
Upstate NY
So I'm focusing my first rig consisting of LED ellipsoidals for the area front lights and I'm noticing an interesting artifact that I'm not used to with incandescent ellipsoidals. The LED elllipsoidals are Source Four LED Series 2 Lustr+ with EDLT tubes. Each individual beam field appears to be extremely flat and even, something we have generally always strived for in our bench focus of incandescent ellipsoidals. However, it is so even that where the beams of neighboring areas overlap with one another there is a noticeable bump in brightness. With incandescent ellipsoidals the brightness of the beam tends to fall off toward the edge of the field so that when you overlap beams you get about the same brightness in the area overlaps as you do in the center of the areas.

Has anyone else noticed this and how have you resolved it? Is there something basic I'm missing? Right now the best answer appears to be to utilize a higher degree of overlap than would traditionally be required (the edge of one beam has to fall through the middle of its neighboring beam). I'm planning to add diffusion to the fixtures which I am hoping will help somewhat as well.
 
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Smatticus

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Jan 2, 2004
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Upstate NY
ETC makes an accessory Soft Focus Diffuser that helps with blending LED fixtures. It goes in the gobo slot.
I have this accessory installed in all the fixtures in the plot and I'm still seeing the artifact/having the issue I'm describing above. Personally, I see hardly a difference when the Soft Focus Diffuser is installed versus when it's not.
 
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derekleffew

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Some pertinent comments in this six year-old thread: https://www.controlbooth.com/threads/led-source-four.27888/page-4#post-250313 :
I am one of the designers of the optics for the Source 4 LED.
First, thank you for the constructive comments.
Second, I'd like to clear up some muddy waters.
1) The field, while it may look flat, has a roughly 2:1 falloff. If you blend two beam with hard edges, there will be a bright stripe where the beams overlap. Placing a diffuser (included) in the gobo slot and soft focussing the lens tube improves the blending.
2) The output of a Lustr+ (color) unit is 4200 field lumens with a 26deg EDLT lens tube. This is for a cold fixture with all channels turned on full, and we (ETC) stand behind that number. Complete photometric data will be up on our website soon.
3) The comparison lumen measurements referred to by derekleffew were taken by myself and another optical engineer in a side room at PLASA last fall. We used a high-quality photometric camera and repeated the measurements for all who visitors who wanted to see. We asked Prism to let us measure a RevEAL profile, but were turned down.
 

Smatticus

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Jan 2, 2004
Location
Upstate NY
Thanks, I saw there was discussion of the fixture optics in other threads but I did not see any discussion of practical focusing considerations for area coverage. I see that a soft focus and the included diffuser "improves the blending" but does it improve it enough that people don't have to utilize other methods to achieve even area coverage in practice? Regardless of what the actual falloff is, if it looks flat to the eye and a "bright stripe" is created with a little beam overlap is diffusing the beam edge really going to help much? It might feather/blend it together but if there is still a bright region that an actor would pass through as compared to the middle of the beam there's still a practical focusing issue. I'm not suggesting there is anything wrong with the design of the Source Four LED or any other LED ellipsoidal out there, but they've been out for a while and people must have developed some best practices for overlapping and blending. What are people finding they have to do to create even area coverage?
 
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Chase P.

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Location
San Francisco
My understanding was that the Soft Focus Diffuser was intended to help sharpen the edges of shutter cuts and remove the rainbowing effect that can occur with LEDs. I've heard them called "beam homogenizers", and indeed "homogenize" seems to be the term used to describe them on the LED Source 4 data sheet (https://www.etcconnect.com/WorkArea/DownloadAsset.aspx?id=10737483869).

There's also a Smooth Wash Diffuser on the Source 4 data sheet that fits into a gel slot. Would that be a more effective solution in this case? Does anyone know how that ETC branded diffusion would compare to name brand gels, and what might be comparable?

Everywhere I work we just stick a R118 or 132 in the gel slot, and use the Soft Focus Diffuser in the gobo slot.
 

sk8rsdad

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The diffusers are holographic lenses so there's no comparable gel; they're optically very different.
 

Chase P.

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Feb 3, 2017
Location
San Francisco
Thanks for that! I'd never used them, so had no clue. Have you? Now I'm really curious about them!
 
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DanH

Member
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Feb 24, 2017
Bench-focus your lekos depending on where you're using them. You can bench-focus the center a little hotter than the edges & fix your problem. We used to have some Kliegs on very long throws where they were shuttered way down tight--we focussed them to leave a hot spot in the center. Saved burning out shutters, too.
Do you usually bench focus them before or after setting the DMX address?

(nudge nudge...we're talking about LED leko's here)

8)
 

DuckJordan

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Doesnt matter
DanH:"Do you usually bench focus them before or after setting the DMX address?" (W don' use no stinkin' DMX--just electricity! )

Seriously, don't the marvelous Source 4s allow the user to adjust them as needed for the application??
Yes the standard Incandescent Source 4s do, but their LED brother does not, Its an enclosed housing space and the "Lamp" is a set of individual diodes (RGBAW?) and traditional Bench focusing is not something that is easily or really able to do at all as changing one LED's distance within the reflector could cause problems for another.
 

Smatticus

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Jan 2, 2004
Location
Upstate NY
Thank you for the feedback so far. If anyone else has any feedback would love to hear it. As of right now I'm putting R119 diffusion in the fixtures. That has nicely diffused the beam edges but I haven't had a chance to really evaluate how well it's helping with the area overlaps. It's interesting that the gobo slot "SOFT FOCUS diffuser" would actually be intended for use when you want the beam edge SHARP. Regarding the Smooth Wash Diffuser mentioned... this video makes it sound like you should really have the Smooth Wash Diffuser to achieve nice area overlapping. If that's the case it's kind of annoying that they don't ship with the fixtures or lens tubes... though I understand why because of the different tube sizes. The D40's and D60's that were purchased did come with the holographic lenses, though we had to specify which spreads we wanted. Has anyone had a chance to compare the performance of these Smooth Wash Diffusers to any standard diffusion gels out there? I understand they are optically different, as was said, but I'm wondering what diffusions are maybe best for the job if you don't have the Smooth Wash Diffusers.
 

SteveB

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Joined
Mar 20, 2004
Location
Brooklyn, NY
Thank you for the feedback so far. If anyone else has any feedback would love to hear it. As of right now I'm putting R119 diffusion in the fixtures. That has nicely diffused the beam edges but I haven't had a chance to really evaluate how well it's helping with the area overlaps. It's interesting that the gobo slot "SOFT FOCUS diffuser" would actually be intended for use when you want the beam edge SHARP. Regarding the Smooth Wash Diffuser mentioned... this video makes it sound like you should really have the Smooth Wash Diffuser to achieve nice area overlapping. If that's the case it's kind of annoying that they don't ship with the fixtures or lens tubes... though I understand why because of the different tube sizes. The D40's and D60's that were purchased did come with the holographic lenses, though we had to specify which spreads we wanted. Has anyone had a chance to compare the performance of these Smooth Wash Diffusers to any standard diffusion gels out there? I understand they are optically different, as was said, but I'm wondering what diffusions are maybe best for the job if you don't have the Smooth Wash Diffusers.
If it makes you feel better, I just received some Vari-Lite 1100's. No Power-Con connectors. No gobo's. Yeah, thanks I thought, remind my why I buy that product ?.
 
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Smatticus

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Jan 2, 2004
Location
Upstate NY
If it makes you feel better, I just received some Vari-Lite 1100's. No Power-Con connectors. No gobo's. Yeah, thanks I thought, remind my why I buy that product ?.
That sucks. I see on the website it says they don't come with patterns installed. What size/type gobos do those take? Do they not include power cords because they don't know what kind of plug you need on the end? I'm not sure that any of the Source Four LEDs we just got had power cords in the boxes, I think those may have been purchased separately.
 

Amiers

Renting to Corporate One Fixture at a Time.
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May 28, 2009
Location
Phoenix, Az
The no gobos sucks but the power cord I can understand.

OG Source 4s come with a bare whip.

And not surprised that the LEDs come without cord. Not to say that they nickel and dime it but if they move 50,000 units in a month and give away a connector with a whip that will add up pretty fast.
 

SteveB

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Mar 20, 2004
Location
Brooklyn, NY
FWIW, the VL1100 gobo's - 5 per fixture, tend to run about $50 each. For my situation it was a fixture specified a good 12 years ago, as we wanted a quiet fixture. Given the current crop of LED and other fixtures, I would not specify this currently.

As to Power-Con. The ETC Lustre II line comes with a 5ft. Power-Con cable with either Twist-Lok, 2P&G or Edison, or bare ends as per user specifications. My new ColorForce fixtures all came supplied with True1 cables and connectors, which is annoying but our mistake in our order specifications. The 24 Elation Satura and Platinum Seven units all came supplied with PowerCon cable and Edison. VarLite supplies and specifies no supplied cable.