# Blue Edge and Brown Edge



## Serendipity (Aug 18, 2008)

Example: You're focusing a Source Four ERS. The designer asks you to run the barrel (you're hard focused currently) and depending on if you run it in or out, the color of the edge of the light becomes more diffused and turns either blue-ish or brown-ish.

Question: Why does moving the barrel in either direction change the hue of the edge of the beam?

Thanks!


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## JD (Aug 18, 2008)

Chromatic Aberration. Lens acts a bit like a prism. (google it) This is why optical lenses such as camera lenses use compound lenses. Hard to get around it on a one element lens assembly.


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## ship (Aug 18, 2008)

This especially if running the barrel it was blue hard edge all around but in other focuses cannot get back to there leads to say a lens train problem - perhaps a lens not properly seated or something but below the steps in troubleshooting I would take.

I don’t have a tremendous amount of experience with S-4 fixtures, can almost count on one hand how many times I have bench focused a group of them at any sitting. Had a few examples of them which no matter what I did, I simply was not able to give the fixture a proper bench focus that I would hope in problem was later solved by those that more normally do so.

Think it’s in part a question of as opposed to say a 360Q Leko that bench focuses in three dimensions, the S-4 only does so in two dimensions. Make sure your lamp is properly seated and hope for the best as a limitation in easier focus but in some ways three dimensional three screw focusing while a pain in the rear has its advantages.

On the other hand at one point I got to service a Lycian 1290 follow spot that someone forgot to strap into the man-lift lifting it up to a lighting position. It fell and in getting back to the shop I gave it my best effort in optically re-aligning it. Got it back to a hard edge and even reduced the double image but end result was that I could not get rid of the half brown/half blue hard edge with a slight halo I expect you in part also see. For me it was the slightly bent frame and reflector warp caused by the fall that required a few $K in shipping and service at the factory to correct. 

Overall, since a S-4 reflector is less able to go out of round and works or won’t I would suspect it’s more about the optical train being straight. This either fully seated lamp - and or properly seated lamp and a frame for that lamp that’s not warped given a cast element or lamp cap fully installed, or perhaps a lens train that’s optically parallel in the lens train.

A few things to be difficult here. First and easiest in troubleshooting is knobs tightened. Second in changing lens trains, third seated lamp. After that and with all bench focus of the lamp in all conditions being adjusted.

Knobs tightened or stripped could make it seem like there but not in a bit of wiggle room. This as with missing lens train glides could allow for a slight out of focus cant. Lenses in the lens train by lot number or ones not fully or properly seated could be at a slight angle, bumpers for them missing etc. Seated lamp being a lamp and fixture question. Hard to get a lamp fully seated and in doing so enough slop in being able to do so that it does so properly. Could be wear, could be bad casting on the lamp or fixture, could be any number of reasons a lamp don't seat properly in a pre-focus socket type this fixture has. Most commonly it's a lamp not fully or properly seated however, or perhaps a bent casting in seating it as less common.

After that, I would suspect the optics of the lamp socket alignment and change a lamp cap with one that is known to work properly in bench focus. Following this troubleshooting concept of it being the lamp base I would if still bad suspect that if I changed cap and barrel, a slight warp to the fixture. I would refine that search in changing out parts until it was corrected.

Should be able to correct this problem, just take a bit of time. And somewhere between all also play with a different lamp in the fixture.


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## ship (Aug 18, 2008)

My near future wife that heads up the Leko department says reflector issue - bad reflector. And while I love to see the microscopic silver confetti coming out of a Leko that’s being blown out by way of a bad reflector, I just cannot see that of a thick glass reflector changing its shape. This granted of course I only get called in on such issues to either remove without cracking a reflector, break the silly thing in being much easier than attempting to remove, or to seat the thing in getting a new one in. Seating is patience and hit or miss and a royal pain in the rear to which only the fist and luck plays a role. Had a jig set up for doing this once but it didn’t work out so well.

Anyway, general concept in being supportive in concept is that perhaps the lens is not properly seated and slightly off. Could be as another thing to check.


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## quarterfront (Aug 19, 2008)

This is perfectly normal. Generally I pick which way to go depending on how I'm going to use the special or just depending on my mood.

You'll also notice that a gobo focused just in from sharp gives darker voids, while just out from sharp gives softer voids.


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## Serendipity (Aug 19, 2008)

ship said:


> And while I love to see the microscopic silver confetti coming out of a Leko that’s being blown out by way of a bad reflector



That did happen to one of our S4 reflectors a tech was cleaning. The silver confetti is not happy confetti. It hurts and gets stuck inside your jacket...

Thank you for your responses! I'm not terribly worried about it (it's not very noticeable) but I was curious why it occurred. And if I have extra time in a couple weeks when maintenance starts, I'll try out what Ship was saying.

Every one of our S4s (that I can remember) does this, so I assumed it was normal, but Ship's comments seem to make it a problem rather than a feature.


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## Les (Aug 19, 2008)

When half of your beam is blue or brown, it is a problem. However, a little blue or brown "halation" around the edge of the beam or gobo/shutter cuts is pretty normal. Donuts can help alleviate this if it is too noticeable.


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## icewolf08 (Aug 19, 2008)

It is my understanding, though I could be wrong, that you should get a nice blue outline around your beam when you have a properly bench focused unit in sharp focus. This, as has been mentioned, is due to different wavelengths of light refracting at different angles through the lens. Here is an image from Wikipedia:


You can see that the colors with shorter wavelengths (the blue and UV end of the spectrum) converge at a focal point closer to the lens, thus, ending up at the outside of the field when you focus a light sharp. Since the reds end up inside the bulk of the field we don't tend to see them. However, as you move the lens to focus and you get closer to the different focal lengths of the different wavelengths you may see some of that color show up on the edge of the field. Hence the red-brown "halo."


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## LekoBoy (Aug 19, 2008)

My teacher says the biggest problem with the Source Four is that it doesn't soften as nice as other Lekos used to. This makes them better for gobos, but harder to use for acting area lights.


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## Sony (Aug 19, 2008)

LekoBoy said:


> My teacher says the biggest problem with the Source Four is that it doesn't soften as nice as other Lekos used to. This makes them better for gobos, but harder to use for acting area lights.



This is true, but in my experience Leko's should only be used as Front and Special (Gobo's and spots) lighting. Fill light (Side, Top and backlight which I assume this is what you're refering to when you say Acting Area lights) should be provided by Frenels and Par's. Front light usually requires more focused light for shuttering and defined facelight to create more shadows and depth.


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## SteveB (Aug 19, 2008)

Sony said:


> This is true, but in my experience Leko's should only be used as Front and Special (Gobo's and spots) lighting. Fill light (Side, Top and backlight which I assume this is what you're refering to when you say Acting Area lights) should be provided by Frenels and Par's. Front light usually requires more focused light for shuttering and defined facelight to create more shadows and depth.



Seems a little dogmatic, IMO.

I like to advise that the designer choose whatever tools - I.E., ellipsoidal, Par, scoop, fresnel, 100w A lamp in a socket, you need for the job and do not pay attention to popular convention or other opinions. 

Experiment until you develop a sense of your own needs and a grasp of what the tools bring to the design.

I haven't had a fresnel in my theater in 25 years. Few have asked for one. If need be, I can make an S4 ellipsoidal do what a fresnel does, but have yet to master the trick of making a Fresnel project a gobo. I prefer ellipsoidals as side lights, as they offer shuttering off legs and scenery. But this is particular to my space and I would never presume to tell someone that a particular type of fixture should "Never" be used for something.

My $.02

Steve B


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## Sony (Aug 19, 2008)

SteveB said:


> Seems a little dogmatic, IMO.
> 
> I like to advise that the designer choose whatever tools - I.E., ellipsoidal, Par, scoop, fresnel, 100w A lamp in a socket, you need for the job and do not pay attention to popular convention or other opinions.
> 
> ...



That's why I stated that it was "In my experience." I personally prefer to stick mostly to the standard...that's not to say I've never tried other methods and fixtures...I just find that the standard way is that way for good reason and IMO is the best. I've used frenels for front light and leko's for top and back light before and I just personally don't like how they look. I do however agree that they are good for side light and such, unfortunately at my college we never had enough lekos to do both the sides and fronts in lekos. I do however enjoy playing with lots of different colors, thats always a lot of fun.


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## Serendipity (Aug 20, 2008)

LekoBoy said:


> My teacher says the biggest problem with the Source Four is that it doesn't soften as nice as other Lekos used to. This makes them better for gobos, but harder to use for acting area lights.



This may be why almost every designer who uses our Black Box rep plot uses frost with our S4 front light system? (The one who hadn't was using striped gobos, which were supposed to be as hard edged as possible.) I hadn't thought about that reasoning before.


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## cdub260 (Aug 20, 2008)

SteveB said:


> ...but have yet to master the trick of making a Fresnel project a gobo.



Have you tried drawing on the back of the lens with a sharpie?


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## derekleffew (Aug 20, 2008)

R114 was sometimes used in 360Qs, but R119 and R132 were invented after the 1992 introduction of the Source4. So your reasoning skills are accurate, 'Dip.


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## Serendipity (Aug 20, 2008)

derekleffew said:


> R114 was sometimes used in 360Qs, but R119 and R132 were invented after the 1992 introduction of the Source4. So your reasoning skills are accurate, 'Dip.



Thanks!  (Yes, R132 is what I had in mind.)



cdub260 said:


> Have you tried drawing on the back of the lens with a sharpie?



Hahahaa. But because the ridges of a fresnel lens are on the outside, wouldn't that just cut the light output of the fixture when the light hits the ridges? Which leads me to wonder, where, if there is one, is the second focal point of a fresnel (spotted or flooded)?

(Nah, what you want to do is draw on the lamp since it's a focal point...  )


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## Sony (Aug 20, 2008)

Fresnels usually only have a single focal point, as far as I know. The reflector in a Fresnel reflects the light beams so they are in Parallel and then the lens refracts them.


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## icewolf08 (Aug 20, 2008)

Sony said:


> Frenels usually only have a single focal point, as far as I know. The reflector in a Frenel reflects the light beams so they are in Parallel and then the lens refracts them.



Only about half of that is true. A Fresnel has a a spheric reflector. With a spheric reflector, all the light is reflected back at the same angle it hit the reflector at (in a perfect point source system). So Yes, the fresnel reflector has only one focus, which is at the lamp, and the light that bounces off the reflector goes back through that same point before hitting the lens.

Parabolic reflectors put the light into parallel rays.


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## JD (Aug 20, 2008)

Projecting a gobo with a Fresnel? No problem, just follow these simple steps:

1) Remove the glass from the bulb.
2) Spot weld the gobo to a lamp support about 1/8 inch above the filament facing the front.
3) Reinstall the glass and suck the air out of the bulb. 
4) Add some inert gas and seal well.
5) Remove the reflector.
6) Replace the lens with a PC lens.

See! Nice gobo projector! (Ignore the big white springs visible on the projection.)


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## quarterfront (Aug 20, 2008)

Projecting a gobo with a Fresnel? No problem.

1) Remove lens.
2) Blackwrap over the reflector.
3) Make a gobo the diameter of the lens.
4) Insert this gobo where the lens goes.

Voila. Linnebach projector. Make the gobo out of glass, you can paint on it.

Okay, admittedly this won't go very sharp. How sharp you get depends on how compact your lamp filament is and the distance from the lamp to the "gobo". And, admittedly, this won't be very bright, a Fres isn't very efficient to begin with and eliminating the reflector cuts, say, 3/8 of what you would normally get out of the mix. But one summer when I was a wee lad doing summerstock I did a production of I'm Not Rappaport using this method to project leaf dapple 'cause I didn't have a bank of lekos to spare and it did the trick.


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## Serendipity (Aug 20, 2008)

JD said:


> Projecting a gobo with a Fresnel? No problem, just follow these simple steps:
> 
> 1) Remove the glass from the bulb.
> 2) Spot weld the gobo to a lamp support about 1/8 inch above the filament facing the front.
> ...



Wow, thanks JD! I'm sure that'll go over great with my Lighting Supervisor...  

Nah, I want to use a Source Four Multi-Par to do gobos, I'm not too fond of our fresnels.


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## ship (Aug 21, 2008)

SteveB said:


> Seems a little dogmatic, IMO.
> 
> I like to advise that the designer choose whatever tools - I.E., ellipsoidal, Par, scoop, fresnel, 100w A lamp in a socket, you need for the job and do not pay attention to popular convention or other opinions.
> 
> ...




Agreed... in a broad sense, re-read USITT tech in the "Go-Fres" about issue #18 if I remember correctly.

Might disagree largely on the use of a Fresnel in general but respect that observation.


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## ship (Aug 21, 2008)

JD said:


> Projecting a gobo with a Fresnel? No problem, just follow these simple steps:
> 
> 1) Remove the glass from the bulb.
> 2) Spot weld the gobo to a lamp support about 1/8 inch above the filament facing the front.
> ...



Not the way its presented (in me getting out the booklet) USITT "Theatre Technology Exhibit 1991". Article 15 by Mark Zetterberg of Central Washington University.

Get it... Learn it - its possible and easy to do in a based on Linenbacher projector type of way...


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## Serendipity (Aug 24, 2008)

Charc said:


> Derek, I'm having trouble following this, just going off the Rosco website, because my swatch books are on the second and first floors, respectively.
> 
> The thesis brought forth by *LekoBoy* states that Source4s, don't soften "as nice" as "other Lekos" used to. Which indicates that "other Lekos" no longer soften "as nice". Additionally "as nice" is hearsay, because it is neither quantitative nor qualitative, simply a question of aesthetics.
> 
> ...



_Dip breaks out the swatchboook..._
Charc's right, that doesn't quite make sense.... Care to elaborate, Derek?


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## cdub260 (Aug 24, 2008)

Charc said:


> Then again, it's nice to use to use diffusion anyways.
> 
> However, Rosco's website states that R114 is a "very light frost", and that R119 is "Lighter than 114", and given the name of R132 "Quarter Hamburg Frost", I'm assuming that is is also lighter than R114, which is named "Hamburg Frost".



I'm rather partial to R-116 myself. Of course, I don't use it in my Source 4's.


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## Serendipity (Aug 24, 2008)

cdub260 said:


> I'm rather partial to R-116 myself. Of course, I don't use it in my Source 4's.



What do you use it in? That's one tough frost... (No pun intended.)


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## derekleffew (Aug 24, 2008)

*'Dip'Oaldabs*, I hope this helps.

The following contains some inferences based on experience and observation, but the historical facts are absolutely correct. Note I am speaking of professional designers working with union crew members and rental fixtures.

Before 1992, designers would focus a wash of ERSs by setting a sharp edge, making shutter cuts, and then running the barrel either slightly out or in to soften the edge. In theory, after the first light was focused, the designer and electrician knew the barrel setting for all the other lights. In practice however, the bench focus of the light played a major factor and sometimes one light would look better with barrel in, even though all of its brothers had barrel out. On order to speed the focus process, some clever designers took to focusing all units sharp, and then adding the lightest frost available at the time, R114.

When the SourceFour became the standard, the practice continued and escalated, as designers saw that the S4 beam was almost too perfect. It was difficult to obtain a soft edge that would blend with its neighbors. So the practice of adding Hamburg became even more commonplace. But never being satisfied, designers wanted a less soft edge than R114 afforded, but didn't want/couldn't to go back to running the barrel. Thus begat R119. After a few years, again designers decided they wanted something slightly less soft, and R132 was born. Choosing from three densities of Hamburg is still more efficient than having an IA guy run the barrel on every light, while 27 other stagehands look on.

It offends my sensibilities to think of putting frost in a template unit, so forgive me if I ignore that. I must ask if same designer also insisted on donuts?

"Frost" is a generic term which may be used to refer to any diffusion, not just R100. I've used the term "Hamburg" above when referring to all three R114, R119, R132. There are rough equivalents in Lee and Apollo. GAM is unique in that they offer 9 different degrees of diffusion, from 10-10 to 10-90. I'm still searching for the perfect diffusion for my followspots. See http://www.controlbooth.com/forums/lighting/5772-ever-put-baggy-followspot.html?highlight=baggy.

For a garage experiment, sharp focus an S4, with shutter cuts. Run the barrel and observe the edge. Put it back to sharp. Now try 114, 119, and 132. Post your findings! Obviously the desired edge will vary depending on the fixture's intended purpose, so this exercize is an abstraction. And we have yet to touch on peak vs. cosine distribution.


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## cdub260 (Aug 24, 2008)

Serendipity said:


> What do you use it in? That's one tough frost... (No pun intended.)



The inkies and GU-10 lights on the frame, and the inkies on the upper stage. Both places need incredibly softened light.


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## quarterfront (Aug 24, 2008)

> Who doesn't spec' diffusion in their ERSs these days?



Me. Used to, stopped doing it because you lose some lumens to the frost.


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## Serendipity (Aug 24, 2008)

derekleffew said:


> *'Dip'Oaldabs*, I hope this helps.
> It did!
> And are we the same entity now? And can't you come up with a better name?
> 
> ...



Here's my ten characters--
Yes, I'm taking up Charc's replying in the quote method, as it's much quicker.


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## OnWithTheShow (Aug 24, 2008)

> designers would focus a wash of ERSs by setting a sharp edge, making shutter cuts, and then running the barrel either slightly out or in to soften the edge.



How would this work? Last I checked running the barrel will move where your shutter cuts are even on a perfectly benched fixture.


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## derekleffew (Aug 24, 2008)

"Template unit" = any ERS with a gobo in it. The gobo goes in the template holder in the pattern slot, and the donut goes into the colorframe holder(s), and the diffusion media goes into the file.

From Apollo's http://downloads.goapollo.com/Color%20filter%20guide.pdf

> AP1200 EARLY MORNING FROST
> 
> A good medium diffusion. Softens
> shutter cuts and harsh gobo edges
> ...


I suspect the missing word [?] is "fixtures" or "ERSs". While I still don't agree with using frost with a gobo, Apollo does help prove my point in a roundabout way about needing frost with S4s. I'm saddened to report this color didn't prove satisfactory in my Super Troupers. The quest continues.

'Dip, see Rosco US : Technotes : Filters : Diffusion Confusion, and http://www.rosco.com/includes/technotes/filters/FilterFacts_06.pdf, pp19-21. While both are geared toward film and video where the edge quality is not as important as in stage lighting, they do explain what all the "frosts" are for. Start a new thread with your personal views on diffusion media.

While searching, I found this poll http://www.controlbooth.com/forums/...ners-gel-holders-not.html?highlight=diffusion, in which our new users might want to participate/comment.


> designers would focus a wash of ERSs by setting a sharp edge, making shutter cuts, and then running the barrel either slightly out or in to soften the edge.
> 
> OnWithTheShow said:
> 
> ...


 Good designers know this, and thus will keep the cuts slightly inward, OR, will have the focuser retouch the critical shutter cuts after the desired edge is achieved. Even when using X132, sometimes shutters need to be retouched. See this post http://www.controlbooth.com/forums/...hat-brand-gel-what-does-cost-3.html#post78866 and a few that follow it.


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## icewolf08 (Aug 25, 2008)

Charc said:


> Who doesn't spec' diffusion in their ERSs these days?




quarterfront said:


> Me. Used to, stopped doing it because you lose some lumens to the frost.




OnWithTheShow said:


> How would this work? Last I checked running the barrel will move where your shutter cuts are even on a perfectly benched fixture.



Most of the designers that come through my theatre don't spec diffusion. They would tell you that it is a mark of a lazy or a Yale designer. Point, cut, blend. That is how we do it. When done right, I think you can get a better blend with more lumens on stage if you get your edge through focusing the fixture rather than using diffusion.

As for the question of moving the shutters, running the barrel does not effect where the cuts are, just how the light moves around the cuts. If you make a sharp cut to a wall and then run the barrel, the cut will still be at the wall, but you may change the "feathering" of the beam to either feather in from the cut (making the wall darker) or feather out from the cut (making the wall brighter. It all depends on how you need your fixtures to blend.


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## quarterfront (Aug 25, 2008)

> How would this work? Last I checked running the barrel will move where your shutter cuts are even on a perfectly benched fixture.



Generally I get the instrument centered, then have the electrician do cuts, then touch the beam edge, and if the cuts drift we retouch. If I know the focus is going to be really tight and has to be "just so" I'll often have them push a shutter a little way in and adjust the edge looking at the shutter. Once the edge is right we do shutter cuts. 

This is pretty much standard procedure, isn't it?


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## Grog12 (Aug 25, 2008)

JD said:


> Projecting a gobo with a Fresnel? No problem, just follow these simple steps:
> 
> 1) Remove the glass from the bulb.
> 2) Spot weld the gobo to a lamp support about 1/8 inch above the filament facing the front.
> ...



You've obviously never worked film.


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## cdub260 (Aug 25, 2008)

Serendipity said:


> Does cdub want to help?
> 
> Here's my ten characters--
> Yes, I'm taking up Charc's replying in the quote method, as it's much quicker.



Sure, I'll help. You know how to find me, don't you?


OnWithTheShow said:


> How would this work? Last I checked running the barrel will move where your shutter cuts are even on a perfectly benched fixture.



I've really only wound this to be an issue with my 5 and 10 degree Source 4's. Except for the whole working 25 ft in the air while standing on a pipe attached to a truss awkwardness, its really easy to just retouch the shutter cut after running the barrel.


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## Serendipity (Aug 25, 2008)

cdub260 said:


> Sure, I'll help. You know how to find me, don't you?


No, I have no idea. "I only live here."


Grog12 said:


> You've obviously never worked film.


Expand, please?


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## thenelsontwins (Aug 25, 2008)

JD said:


> Chromatic Aberration. Lens acts a bit like a prism. (google it) This is why optical lenses such as camera lenses use compound lenses. Hard to get around it on a one element lens assembly.



Agreed, this is your issue, which isn't really an issue at all. They will always be there. 

But I also agree, a good bench focus never hurts anything. I wish I could get the shop guys to figure that out.


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## OnWithTheShow (Aug 25, 2008)

> just retouch the shutter cut after running the barrel.



Right but this isnt what was said. It was said make the cuts then run the barrel. It should be cuts, barrel, cuts. Just like crossing the street.


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## ship (Aug 25, 2008)

Charc said:


> I'm really intrigued by this idea, but it feels a little too home-brew for me. Anyways else have any comments on a DIY Linnebach? PMs accepted, for electrical safety reasons.



I made a Linebacher projector out of two Century 8" #1560 Lekolights. This by way of removing reflector and lens train plus gate from the cannon of a fixture. Large painted plexiglass screen that was optically arranged than spiked into place at a focal point that in the location did its best effect. Than the stray light was blocked after focusing. Basically it was a slide with behind it a large wattage lamp at a focused proximity without reflection and refraction.

Worked well - loved the effect though for these lamps the filaments were large enough that they didn't do such a great graphic effect. Shielding for the lamps was nominal in this case given huge (discontinued) filament incandescent lamps and in general placing the fixtures away from people - this plus the shielding of them for light escaping.

Smaller filament will have worked for a more graphic image but also given throw distance and size of it it played a role. My throw distance was short and size large, this with filiment that was large worked well for projecting a less realistic image with painted slide. - - REally just black paint on plexiglass and it worked to the effect given the background and a scrim.

Overall, more lively in look than that of a gobo and for the most part wider in focus than possible - this much less given the fixture location, would not short of a very custom gobo and wide focus fixture.. it looked better in the end in showing a natural effect that gobos from a single source could not do realistically. Sharp angles like this I had - only a few feet between stretched screen and scrim need the ability to aim the slide to focus it properly. Not true Linenbacher - got three of them on a storage shelf, but effect done in simply manually focusing the painted large slide than spiking it in place.

Electrical safety... for me it was incandascent. If you need to 1" chicken wire the frame of the fixture or rope off the area. Beyond that, its an old effect that some computer programming and special money paid could achieve.


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## LightStud (Aug 26, 2008)

ship said:


> I made a Linebacher projector out of two Century 8" #1560 Lekolights. This by way of removing reflector and lens train plus gate from the cannon of a fixture. Large painted plexiglass screen that was optically arranged than spiked into place at a *focal point* that in the location did its best effect. Than the stray light was blocked after focusing. Basically it was a slide with behind it a large wattage lamp at a focused proximity without reflection and refraction.


Since you used two 8" *Lekolites*, did you make one or two *LINNEBACH* projectors? A unit with no reflector or lens, and per your own words no reflection and refraction, cannot have a *focal point*. The best commercial Linnebach projectors were made by Kliegl Bros. as late as the 1970s, and used a 65V, 2100W T24 Mogul Bi-Post lamp. A dimmable transformer was included. The slides were huge, maybe 24" x 36".


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## ship (Aug 26, 2008)

LightStud said:


> Since you used two 8" *Lekolites*, did you make one or two *LINNEBACH* projectors? A unit with no reflector or lens, and per your own words no reflection and refraction, cannot have a *focal point*. The best commercial Linnebach projectors were made by Kliegl Bros. as late as the 1970s, and used a 65V, 2100W T24 Mogul Bi-Post lamp. A dimmable transformer was included. The slides were huge, maybe 24" x 36".



I made two of them - the cannon lower part of the fixtues lens train from gate to gel frame removed on them is about 16" wide. Reflector removed you have a shielded 16" single focus filament source projecting against a pattern. Only from there is a question of filament efficiency, projection and frame that’s optically aligned. This given most of the fixture removed.

As said, what I did was not optically a slide projected, more like an image projected of fitting to the ethereal nature of the shows.

Ah.... “Cannot have a focal point” Not my words certainly given many lighting fixtures of the past without reflectors and or even some without lenses - focal point is the filament. That’s a simple answer common to the concept of this type of projector in why you remove them so as not to get double and more images or why one puts a gel where its located.

Imagine this slide where it’s placed at the place where the beam is most efficient to project that beam of light out of the filament only source. Lots less efficiency but also a sort of naturalistic type of projection.

My slides were about 24" square also.

Main concept... it worked and looked darned good! Could do so especially with a Fresnel but also with the lower half of a Leko.

It’s a concept in a lively artistic projection. If you want reality, go projection - just calculate properly the exact angles and have a wide enough fixture or get stuck projecting from the front instead of adjusting the plate to the angle of projection you need. Sure what’s close will be more refined which you can correct for but overall, worked really well. Does work, just gotta be there in trying such a thing. Huge silide.... yep, it was, on the other hand a bit more easy to paint.


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