# Technique for Bench Focusing 360Qs?



## dwsobel (Oct 15, 2003)

Hey all! 

I'm just about to clean and bench focus an inventory of 360Qs -- x12 up to x16 and some 6" fresnels...what is the proper technique for bench focusing these instruments? Thanks all! David S.


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## wolf825 (Oct 16, 2003)

dwsobel said:


> Hey all!
> 
> I'm just about to clean and bench focus an inventory of 360Qs -- x12 up to x16 and some 6" fresnels...what is the proper technique for bench focusing these instruments? Thanks all! David S.




Hiya David, 
Ahh..well bench focusing 360Q's...that should be a question of the week. Well to give you a rough starting point--you want to be able to set up the instrument facing a blank flat white or light colored wall--or at best a wall with a sheet on it so you don't have cinder-block ripples throwing you off at first. The fixture should be about 10'-15' from the wall at most (IMO---a good estimate is 8' for a 6x4.5, 10' for 6x9 and 12' 6x12's, and 15' for 6x16's) so you get a decent consistant beam spread but its not huge, or worse--too small to see the field.

A GREAT way to set up a permanent bench focus chart on a wall is to draw a + crosshair center of the sheet or wall area, so you have a reference point to aim for that is flat and even with the position of the unit--IOW, the unit is not at an angle shooting up or down to the wall which will slightly skew your focus--but is on even plane. To set this up--make yourself a "bench" with a T pipe, or a regular pipe and base will do. The fixture hangs from it and focuses 90degrees straight to the wall. (You can do this upside down for space if you cannot underhang--so overhang it on the pipe). Mark your hanging point on the base and measure from floor to hanging point--the center of the lens, then go over to your wall and make that same point from the floor to the center of the lens. You want a straight shot from your fixture--not at an angle if possible. That is where you put your + crosshair mark. Make it a nice size so you can see it for reference--about 6" in size. Its just a reference point and keeps you from having to futz with what is center and you can see reference mark to hot-spot better. Ideally, then you can draw a circle around the +, that is even from the center + for reference..but IMO its not neccessary. The center mark should just work fine for you... This way--every fixture you hang and bench focus will be at the same, or close, center on a straight shot and you have a reference point that is close to or similar to the hang position so you can get a straight shot that is not skewed or keystoned off to one side. I've seen some focusing walls that do beam spread circles based on instruments, distance and degree of instruments--but that is for a permanent place and I don't know many places that have a permanent bench focus wall and set up...tho I used to.. 

You basically need to hot spot the unit with as sharp a focus as you can get with all shutters pulled out, then adjust position of the hot spot to center from left, right or up/down, and then once you have the hot spot close to center or dead on, you want to bring the flatten the field even so you blend it evenly to as close a flat-field as you can get without loosing lumens(brightness). Flattening the field is done inside the unit when you turn the screw you basically push or pull the lamp in or out of the reflector in incremental amounts. BE GENTLE..some of the caps will jar around a lot and you could blow a lamp or two when doing this. It happens--have some spare lamps on hand and other fixtures to bench while the blown one is cooling. *(NOTE: NEVER touch a hot freshly blown lamp--its VERY VERY hot and dangerous.) * This way as you flatten the field you have no one side of the unit that is darker then the other side and it is as close to even as possible. Its OK to have a little hotter in the center--and some of the old lenses and reflectors that have been banged around a bit tend to make it difficult to get anything BUT that--so do your best. As you do this and mess with the screws or rings, you will see what I am talking about--and be able to see on a white sheet with your reference mark how the field spreads to fill--and when you have gone too far past the flat field--you will start to get a lot darker a circle. If that happens--reverse and do it again until you are as close to even as you can get without being blaring in teh center for hotspot with nothing else for light in the circle.

Everytime you change a lamp you technically should bench the fixture. Sometimes this is easily done in the air by pointing the instrument straight down and roughing it in...but I've seen quite a few folks who swap lamps and don't bother. Its all a matter of time they want to take I guess.. When you are done with benching--final test in my view is to drop a piece of RED or medium blue or Sangria purple gel in the fixture--a medium deep color but not too deep like R83 congo...and if it doesn't burn thru the gel in a tight spot within a few minutes then your focus is flat and even or close to it. If it does burn right thru--flatten your field more, or you will have gel burn out problems with that light. 

On the back of the 360 caps (old style ones) there are 3 recessed screws (for horizontal, verticle and hot-spot/flat field), and one protruding screw with lock nuts on it (this helps secure the base to the lamp base so it doesn't jiggle around mostly). On the newer 360Q speed caps you have a protruding dual center knob/ring system, with a center flat-head screw in the middle for tightening down, that does similar for bench focus. Which style caps do you have, or a combo of both?? Let me know which caps and if you need more info on adjusting them...

Others may have some other tips or tricks or details to add to this..so make sure you check back. I think I just gave you the bsics tho..tho I'm sure if I forgot something others will catch it. Hope this helps...happy benching. 

-wolf


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## cruiser (Oct 17, 2003)

I have to say... we have never been taught, let alone heard of bench focussing out here!!

I have asked a number of techs but none have heard of it, even the operations manager of our theatre who has been a lighting tech since the dawn of scopex!
We do th regular cleaning and replace dodged lamps etc. after shows have been in and will refocus them back to an "original state" which is defined by the head tech, then they are re hung into our standard rig. 

This is all veyr strange!! ahaha


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## wolf825 (Oct 18, 2003)

cruiser said:


> I have to say... we have never been taught, let alone heard of bench focussing out here!!
> 
> I have asked a number of techs but none have heard of it, even the operations manager of our theatre who has been a lighting tech since the dawn of scopex!
> We do th regular cleaning and replace dodged lamps etc. after shows have been in and will refocus them back to an "original state" which is defined by the head tech, then they are re hung into our standard rig.
> ...




Bench focusing is done to re-align the lamp and socket to center and even out the focus of the light thru the reflector/lenses. Every time you replace a lamp, the focus adjustment of the lamp in the fixture is different from the previous alignment. It may be slight, or it may be extreme. This proceedure is done to align the lamp for optimum output. Ideally and technically it should be done after every lamp change out to check alignment--however in my experience you should check alignment of lamps anytime you notice the lamp output is weak or offset...and annually its a good idea to do it at least 2-3times per year as fixtures get knocked or bumped and the caps may not get seated back right it will surely get noticable. If you have ever wondered what those little screws, or the two ring knobs on the back of a theater fisture are for--now ya know.  My suggestion--pull down two of your lights--try bench focusing one and see if you notice a difference. 

Ain't this website great--ya learn somethin new every day. 

cheers,
-wolf


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## ship (Oct 18, 2003)

While Wolf's post is very proper, I have to disagree with it's actual use.

On bench focus, the 10' target idea is a good goal, I have also heard of placing a piece of paper in the gel frame and the rest of it I forget, something about seeing how the light looks and being able to observe easily how the beam is centered. Think the first place I saw that was on Lighting Network a few weeks ago. This is an actual alternative way to do a bench focus with something in the gel slot and it should work just as well. This if anyone is interest, I could dig up and post a link to it. The principal seems just as sound as focusing a light 10' away and might be of use in keeping the gel cool in verifying that the convergance of the beam is not in the gel frame holder area.

2 to 3 times a year on this 10' proper bench focus, - ambitious and noble but un-realistic. Most people if the fixtures are hung just do it somewhat when they change lamps, or bump them hard at best and when there is time. Others if the fixtures always come down, do a quick focus test before they go back up but certainly don't have a proper bench focus ever. Granted the S-4 has made it a little more rare that a lamp will be harshly out of bench focus. For the most part, lamp quality and base style these days has improved in any fixture to the extent that the lamp you replace is going to be about the same bench focus. Observing what your lamp looks like on a flat surface should be fine to verify it without a proper bench focus. Once a year for a proper bench focus might be a better goal. Same time as you clean lenses and fixtures. 

For now, Wolf has a good step by step detail in it from what I read of it in sounding like what I read and remember from text books. Sorry but I only skimmed it however. I don't think I have ever done a text book proper bench focus, but I’ll add my copy of how to do it from ETC and Altman below.


For me, two things come to mind that are supplementary notes to the bench focus Wolf presents. 

One is that a 6x16 focused at a target 10' away is going to be a bit outside of it's stage focus range, and much different in beam than a 6x12 much less 4.5x6. No matter how it looks at that range, at it's effective and used range, it just might not have the same proper bench focus when given the same target range. Yes, the lamp will be centered and for the most part right, but you probably won't be able to get the required hard edge on the beam. Also, given the focal length, the beam might be a bit more bright than is easily able to see what is dim and bright in it's even spread. A better idea that many point out is to target your fixtures at optimum range at a source such as at a scrim from it’s hang position, and observe what the beam looks like with a hard focus. I would assume that the hard fast 10' rule was written that way so as to keep it simple and easy to make an accurate accounting for what it’s doing because it really does need a target perpendicular to the source and other things about it, but realistically, not many people use the method.

Another small point is that instead on a bench focus of looking at one point of aim, I perfer to swivel the beam up and down to truly see what the beam of light looks like. Your brain and eyes far too quickly adjust to and even out those little dark spots in a beam of light for you to perfectly adjust for them. Were you to swivel that beam up and down, since the dark spots are going light to darker, you do tend to notice them quicker and easier. It might be a test to add to the proper or any bench focus. Than of course, if you go with the new style HPR lamp, you don't have those dark spots in the beam all other lamps will have. But that's another issue.

By the way, the Altman 360Q series is superior in it's ability to adjust than that of the ETC S-4 fixture in my opinion. Just had some this past week that I was on an off occasion trying to bench focus - at least my working version of doing so. Couldn't get them properly done because it's not possible with a ETC fixture to do as much with the focus. Sent the fixtures out with a noticeable bad bench focus, because there was noting I or the person in charge of that area that makes her living off focusing such lights could do about a bad bench focus or something else, given we endlessly attempted to adjust it's knob, changed both lamps and bases and nothing would correct the beam. Granted, the 360Q was also able to get way out of focus easier. For the most part still, a FLK lamp is going to have the same 2.3/8" Lamp Center Length as the one you took out. As long as it is seated properly, and there is nothing wrong with the lamp base or the focus position of the last lamp, the next one should be fine. I don’t even think other than a major fixture breaking bump is going to knock it out of focus given the center lock screw is down. I believe that bench focus proper rules were written long before halogen lamps came to market and for the most part are not of much value anymore as officially stated. That’s my opinion at least. Never had much use for a proper official bench focus. Sorry Wolf.


Altman’s Bench Focus notes and others on the subject of interest:-
Lens Cleaning: to gain access to the lenses for cleaning, or other purposes, remove the lens adjusting knob and slide the lens holder out of the unit. Remove the lens retaining ring and carefully remove the front lens. If necessary, remove the lens spacer and remove the rear lens. (It might be necessary to use rubbing alcohol or soaking the lens to remove it) Reverse this process to install the lens holder back into the unit. NOTE: be sure to note the position and orientation of the lenses before removing them to assure correct reassembly and optical correctness of the fixture. Clean the lenses with mild soap and water or a commercial glass cleaning solution and a soft, clean, lint-free cloth. Insure that the cleaning process does not leave film on the lens, since the heat from the beam will bond the film onto the surface. (Vinegar or any other Coffee Pot cleaning chemicals also work well. Also, a freshly washed lens will smoke a little when used for the first time if not rinsed well enough. This smoking is also leaving a film on the lens which will attract dirt necessitating more frequent washing. 
Beam Adjustment and Lamp Centering: The beam may be altered in appearance utilizing the three flat head machine screws in conjunction with the round head machine screw which acts as a tension mechanism for the three screw mounted lamp base. In some cases this fourth screw has been replaced by a spring. The “hot spot” may be increased (peak field) or deceased (flat field) by moving the socket mounting plate towards the front or rear of the fixture respectively. This is accomplished by loosening the round head machine screw a few turns, then by moving the socket mounting plate towards the front or rear of the fixture respectively. This is accomplished by loosening the round head machine screw a few turns than be alternately adjusting the three flat head screws, the field can be adjusted to the desired look. The lamp should also be centered during this procedure, again using the three flat head screws to “fine turn” the field until the hot spot is centered in the beam. Once the desired field has been achieved, tighten the round head machine serew to lock the socket mounting plate inot position, then tighten the two nuts on the round head screw onto the socket cap to prevent the screw from vibrating loose. Caution: always insure that the lamp is centered when using the iris. A lamp imaged onto an iris will cause premature iris failure. Also when using an Iris, close the shutters down as tight as possible on the cut of the Iris to absorb some of the heat off the iris. 

Lenses - Focal Points: The relationship between the positions of the light source or the object (slide,) and the point where the transmitted rays from an image is determined by the “Lens Formula.” When P = the distance from the object to the principal plane of the lens, Q = The distance from the principal plane to the image, and F = The focal length of the lens; than 1/P+1/Q=1/F.

Focus of Focal Center: when the source (given the lamp is out of focus with its reflector,) is moved forward from the principal focus, the reflected rays converge. When moved back from the principal focus, they diverge with a dark spot in the center of the beam. Also a bright half or partial moon like figure hanging around the center of the beam, denotes a lamp horizontally out of focus with the reflector and its lenses in the opposite direction as is shown

Radius and Focal Length: Lenses are about .52 times their focal length by radius of curvature of the lens. For ellipsoidal lenses.
The Iris of a Spotlight, when the spotlight is flooded, (by moving the filament towards the lens.) The Intensity at the center of the beam will drop to 1/10 of its original focused amount, and if at the same time the iris is closed to keep the spread of the beam or the diameter of the area lighted the same. Dimming the light can be effected by manual mechanical manipulation.

ETC’s Bench Focus
The Difference between ETC Source Four ERS Fixtures and Standard ERS Fixtures:
Measuring Cosine Field Lumens: (The Proper Bench Focus) If carried out correctly, using a calibrated lamp, this test should have a margin of error of about ±5%. To make this easier use the form below and a calculator with a square root function, a light meter and a tape measure.
1) Set the fixture up and focus it perpendicular to the wall. Adjust for cosine distribution, centered within the field, with sharp focus. For best results, the fixture should be at least ten feet from the wall.
2) Draw a line on the wall, bisecting the beam mark beam center.
3) Measure the distance from the front lens to the wall, in feet. Enter the center line distance in the box provided.
4) You need to take readings at center, at 1° and then every 2° off center, to one side only. To find where those points lie on your line, multiply the center line distance by the tangent of each angle. Enter the result in column A and make a mark on the wall for each angle.
5) To find the throw distance, measure the distance from the lens to the mark for each angle (apart from the center.) For each point, add the center line distance squared to the distance off center squared, and take the square root of the total. Enter the result in column B.
6) Place your light meter, with its back flat against the wall, and take a footcandle reading for each point. Enter the result in the footcandles (measured) column.
7) To find Candelas, enter the throw distance from column B and enter it in C. Multiply by footcandles, and enter the result in column D.
8) To find Beam Lumens, multiply candelas by the zonal constant for that angle. Calculate only the values where the footcandles figure is 50% or more than the footcandle reading for the center of the beam. Sum the result.
9) To find Field Lumens, multiply candelas by the zonal constant for that angle. Calculate only the values where the footcandles figure is 10% or more than the footcandle reading for the center of the beam. Sum the result.
10) To find efficiency, calculate the total field lumens as a percentage of initial lamp lumens, if known.
11) Individual lamp lumen output can vary by up to ±10%. If you used a calibrated lamp, you should now scale the readings taken to correspond with the lamp’s Nominal Lumens, as stated in the manufacturer’s catalog. 



By the way, I had actual reference data on these sources with publishing dates and other info such as would be in a bibliography. They are all gone in my lamp notes file now for some reason, be it from the upgrade, or from some simple stupid mistake. I can no longer find them - just a bunch of error lines running across the bottom of the last page. Something like 600 sources with page numbers in lamp notes are now gone - at least for the moment. 

I am reminding such a thing to all of you because a back up on anything you want to keep is crucial. Everyone knows this, but how many people actually do this and as much as recommended? How pissed do you think I would be now had after 5 years of research into lamps, I was suddenly missing my entire biblography for a hand typed 2,386KB file. Now, I'm concerned as to what happened, but know I have a good backup.

For me, it means Monday, I’ll go to work and E-Mail myself a fresh copy of the lamp notes since they have not changed since the last time I sent a backup out. Had I not a computer at work to store stuff on, I would be using a tape backup. Everyone that want’s to save stuff needs some kind of backup and to use it. If you have something you can't loose, you need to get into a force of habit in backing it up either automatically or manually such as I do. 

I made a change to some lamp prices, and to a lamp chart used for some projector lamps today. At the end of the day, I shipped the files home so that there is another copy not only at work but at home and in both E-Mail systems for backup. Even if you only E-Mail yourself stuff, anything to save important info can help. Writing a term paper, how about E-Mailing yourself a copy each night you progress with it to ensure that if something crashes, you can get that info off another computer by accessing your E-Mail.

Just a reminder to backup what you want to keep or you just might loose it. One side note on E-Mailing stuff back to another computer. If it has a different printer, you must shut off the reformatting sequence that will happen each time you open the file or it will add a few hidden bits of memory to your file that after time will eat up your file's space. That's a bad thing that I learned about the hard way.


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## wolf825 (Oct 18, 2003)

Hi Ship, 
Missed seeing ya the past few days...been busy with watching the Cub's games?  No need to apologize for disagreeing...experiences and opinions vary--I stated my experiences and knowledge, and its best to share all views and let others try and decide for themselves. You posted some great information as well! FWIW, the info about 10' is the "base" distance info I have always been taught simply for the reason that not everyone has the space to do it properly for beam length of every instrument--and I did post a technical note that says 15' minimum for a 6x16, tho even I find that a bit on the slim side. But I know ya just skimmed my post--so no worries if ya missed that. I had heard once about the paper in the gel slot idea...but IMO that wouldn't do a proper focus for the resons you stated about beam focus not happening inside the light right at the lens. Plus IMO thats a firehazard to do  

Great info Ship--glad to see ya...
-wolf


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## dwsobel (Oct 19, 2003)

Thanks for all great info! Once I'm done, I'll tell you how it went. Got a couple shows coming up that might be a little hectic teching. David


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## ship (Oct 19, 2003)

Ok, I stand corrected. It must be a long time since I have really used the fixtures because now that I read Wolf's posting about the bench focus, for the most point, its' spot on. Especially "Bench focusing is done to re-align the lamp and socket to center and even out the focus of the light thru the reflector/lenses. Every time you replace a lamp, the focus adjustment of the lamp in the fixture is different from the previous alignment. It may be slight, or it may be extreme." 

I now remember little details about warn lamp bases that allow the subsiquent lamp to seat in a different position than the last one - probably why the S-4 fixture has that comfounded keyway type slot on the base and lamp that does not work well especially on new S-4 Par fixtures before it's warn in. In addition to the play in Leko lamp bases, there are also details about the seat on a 360Q lamp cap seating in the design position, springs and screws hanging up at other than their set position once you install the new lamp, etc. So Wolf, I have to hand it to you, your post reminded me of a lot of details that I forgot. Still not sure about the target method you post being what would be the way I remember it, or the same way I would do it, but pulling the fixtures down for a good bench focus at least once a year it would seem is a good idea given lamps probably only need one change per year.

And it is a lot easier to give a fixture a proper bench focus while not on a ladder. I remember a few times that I adjusted that lamp right into the side of the reflector making it break. Too much tinkering on a ladder with the lamp base should be avoided for more than very small adjustments. Might be better if you find your lamp dead, to install the lamp in a indexed fixture that is perminant to the shop. Than once the lamp is centered in the indexed lamp base, pull the lamp and lamp base and install it in the Leko with the bad lamp. That way, it's probably going to be very well adjusted and while in the shop you can give the lamp base and it's contacts a good inspeciton proper. Good lamp properly centered on a lamp base should when inserted into a fixture in the air, be accurate enough to be servicable.

Of note on the bench focus, instead of wasting time with a horizontal pipe to mount the fixtures at a set location, the place I work uses bench vises to clamp the C-Clamp a bit faster. As long as you alternate which side of the vise you mount the fixture, it's a lot faster and easier.


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## WrecksCars (Mar 14, 2004)

The art of Bench Focus actually dates back to the Romans. 

Okay, okay, maybe not, but it seems that way to me. I know it predates 1980, because we used to do it at that time when I was majoring in Lighting Design at the North Carolina School of the Arts.

Since I haven't seen this posted so far, I'll leave it with you and do another post on the configuration as soon as I hear from a friend who can refresh my memory on how we did it.

We used the same basic setup as Wolf, except we used a lens barrel with---I think---two 6X9 lenses REVERSED in the barrel. This produced a sharp pattern of the "reflector" and the lamp filament on the wall, which allowed us to position the lamp directly in the "hole" of the reflector.

Since I spent my career in television, I haven't done this in years, but when I get the details from my bud, I'll post them.

I'd say try this and see what you get. If you don't get the reflector pattern on the wall, try a pair of reversed of "12" lenses---or a combination of a 9 and a 12---and see what you get. When you get the reflector pattern, you know you've got it right.


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## ship (Mar 15, 2004)

Very interesting idea - reversing the lenses. Can’t wait for the further post on it.


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## Mayhem (Mar 15, 2004)

cruiser said:


> I have to say... we have never been taught, let alone heard of bench focussing out here!!
> 
> I have asked a number of techs but none have heard of it, even the operations manager of our theatre who has been a lighting tech since the dawn of scopex!
> We do th regular cleaning and replace dodged lamps etc. after shows have been in and will refocus them back to an "original state" which is defined by the head tech, then they are re hung into our standard rig.
> ...



I concur!

So, what fixtures need this attention? Is it just ellipsodials/profiles?


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## wolf825 (Mar 15, 2004)

Mayhem said:


> I concur!
> 
> So, what fixtures need this attention? Is it just ellipsodials/profiles?



Hiya, 
Its profiles/ellipsodials...and most moving lights...those need a bit of an adjustment or two when lamps get swapped.

Fresnels don't need it that I have ever run into.... 

-wolf


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## mrex (Apr 3, 2004)

Read through this thread in entirety. Very helpful info here! SO good it made me join in on the fun and register! Hoping to partake in some good exchange. I will try some of these suggestions when we give our inventory a much needed bath here. I'm new at our facility, and this will be the first time our updated inventory (cycled through the past three years) has been touched.... blechhhhh.

joy and rapture,
REX


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## doggmann (Apr 6, 2006)

Gawd, I love this site!! I've learned so much just from the few posts I've read tonight. Can't wait for the follow up post to this topic!!


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## Mayhem (Apr 6, 2006)

mrex said:


> Read through this thread in entirety. Very helpful info here! SO good it made me join in on the fun and register! Hoping to partake in some good exchange. I will try some of these suggestions when we give our inventory a much needed bath here. I'm new at our facility, and this will be the first time our updated inventory (cycled through the past three years) has been touched.... blechhhhh.
> 
> joy and rapture,
> REX




doggmann said:


> Gawd, I love this site!! I've learned so much just from the few posts I've read tonight. Can't wait for the follow up post to this topic!!



Now that is what we like to hear!

Depending on how you have your preference set, will determine how far back in time you see posts. There is an “archive” link at the bottom of the page that will allow you to see the full list of topics.

Of course, there is always the search engine which covers all posts and topics as well.

Welcome aboard to you both and I hope that you enjoy what the site has to offer.

Oh – almost forgot to mention the related topics links at the end of most topics (except this one LOL). This is often very helpful. Especially with subjects that span multiple topics. In addition to this one, look up the fixture cleaning and maintenance topics as well. There are probably several different ones and each should offer something of value.


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## Lightingguy32 (May 2, 2006)

The only down side to the ETC Source 4's Peak/Flat adjustment knob is that occasionaly it will be very tight and you need a wrench to rotate it, other wise i tend believe a Source Four is easier to focus


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## ship (May 3, 2006)

In following a general concept, once the hard edge is as good as seemingly possible, and field as flat as possible I open the fixture, adjust the lamp back to center on the reflector, than re-bench focused them in checking again also. It's a really bad thing if you get what seems to be an optimum beam of light but somehow the lamp globe touches the reflector thus blows sooner. The lamp should not touch the reflector.


Also of note is that I recently did a study of the differences between a HPR and GLC lamp. The GLC has a smaller filament thus should be more optically pure. On the other hand while larger filament, the HPR has the internal reflector that completes the ellipse in making light given off by the larger filament more efficient. At this point, I don’t know what’s the better lamp between a HPR and GLC in being more optically pure verses more efficient.

360Q fixures... pain in the rear to bench focus when starting from scratch. On the other hand, given the HPR or GLA series of lamps, they have become much more efficient. These a long way from the EHD series of lamp in "Altman dark spot" type fixtures I am used to in being much easier to bench focus.


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## gafftaper (May 4, 2006)

Wow, I thought I knew how to focus an instrument. But the truth is I've always just sort of messed around with the knobs until it looked ok. Never thought about taking it down and doing the whole light meter routine. This is a great thread. I've now copied it into my "future lecture notes" folder. Thanks guys.


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## Chris15 (May 4, 2006)

gafftaper said:


> Wow, I thought I knew how to focus an instrument. But the truth is I've always just sort of messed around with the knobs until it looked ok. Never thought about taking it down and doing the whole light meter routine. This is a great thread. I've now copied it into my "future lecture notes" folder. Thanks guys.



I thought that it was about getting this properly centred inside the lamp so that you don't get hotspots and burn through gel...


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## ship (May 12, 2006)

Further thoughts on the recent bench focus.

Anything can be bench focused, just a question of how much time you have to tinker and how accurate you choose to be. More modern fixtures or newer halogen types mean lamps that are within better tolerances of not needing to be bench focused every time they are installed for the most part. S-4, SL and others, you don’t always have to re-bench focus as long as seated completely. A really good way to learn about bench focus or practice it is on a follow spot. Take your time with the intense beam of light in trying to get a totally flat field and blue hard edge ring on it. Once you learn how to make it optimized, what beam of light you are looking at will also be the optimum goal for the Leko.

In my latest fixtures bench focused, I was using the HPR lamp in them. It for the most part did not matter how much I messed with the bench focus on two out of four fixtures - one below described below in having a brown half moon to it’s hard edge, the other with the wrong lenses which would not get a hard edge, the HPR lamp gave a clean crisp beam of light with even field no matter what I did to them. In the case of two out of four, they easily acquired their hard edge witout any work on bench focusing. This lamp as long as the venu has the cash for high output/short life lamps might solve a lot of problems with lack of ability to or time to bench focus the fixtures.

Too bad it’s a high output lamp and not yet available in long life. Much less it’s based off the HX-600/FLK and not the GLC with a smaller fillament. Once it gets the more refined filament much less has the long life option, it’s going to be the fifth generation in lamps for some TBA fixtures which as a internal reflector lamp type hopefully some day will also be available for the HPL series of lamp. S-4 fixtures with 15 to 20% more output and with an even more flat field of light will be very impressive in that brand of fixture some day in a similar way to how improved a 360Q is at least with a HX-600 over that of a EHD. For now it’s just the 360Q, Shakesphere, SL and Selcon as main brands that can use this lamp Still the filament of the HX-600/FLK - this upgrade HPR lamp with internal reflector is huge in comparison to that of a GLC lamp or HPL lamp by way of flat field and output. Good question what’s more optically efficient, that of a GLC, HPL or HPR in projecting patterns however given the HPR has a less efficient filament size or compactness.

In the case of warped lamps thus the need or necessity to re-bench focus every time it’s re-lamped, sometimes in older lamps while the cement lamp base to lamp was setting up the lamp globe would settle at a off angle. Much more rare these days for a Leko lamp and something that if noticeable in warp should be returned to the vendor rather than used. The old projector now Leko lamps were also a little less refined in at times not aligning by way of slightly twisted filaments to the pre-focus base or slight angles to them in the above an off axis way. This tilt to the lamp in old stuff perhaps not as bad as a alternative modern brand of MSR 700SA type moving light lamps I once was buying where there at times would be a 5 degree angle off access tilt to the globe - quality control and even bubbles in the nickel plating of the lamp base made the cheaper lamp no longer cost effective. As concept, in old Leko lamps this accuracy of manufacture where the lamp would not be aligned on an axis to it’s base or to specification in focus LCL length. (Lamp center length, in other words from a fixed point on the base be it the alignment fins or bottom of the pins dependant on the lamp base type, to the center of the filament - that length is the LCL.) 

In doing the below radial Lekos for the theater, it was amazing how not only was I finding Fresnel lamps (2.3/8" LCL instead of 3.1/2 LCL lamps) in them = now there is something that can’t be bench focused, I also found some very ancient Fresnel lamps. Have to do a photo of one of them which 40 years later still works. Has a big brass base around it covering about 1/3 the over all lamp length with an asbestos pad between bulb and brass support structure for the lamp. Never seen anything like it before and I have seen lots of old lamps.

In bench focus or how much time spent, is also in part an answer to what’s good verses perfect. I recently spent one night in me chasing a slight off center brown part of the blue ring around a very hard edge for about an hour before giving up for one of my 3.5Q5's. Must have been a lens slightly off kilter because I replaced all the lenses with chips in them. Other than that, unless the entire fixture has a slight warp to it, I tried every thing in bench focus to get a completely blue hard edge all around the beam. Once done with my own fixtures, I have about 18 radial Lekos next on my to do list that dagnamit will be bench focused once I’m done replacing or re-surfacing all their parts. I’m going to optimize them or quit lighting. Why bother totally resurfacing and wiring them unless they get back to factory spec? I have no idea of what a really factory new condition radio Leko should look like once really time spent on it in bench focusing. Should be interesting because I know what one should look like that has not had a good service call in 20 or more years.

In blue hard edge rings with a 1/8 moon say ring of brown about it, I once had the chance to play with a Lycian 1290 follow spot someone had forgotten to strap down onto the Geni Lift while lifting it up into a truss tower. Yep, the thing took a dump. In adding all kinds of shims so as to get it back to some form of bench focus, it still had a brown ring no matter what I did to it. Cost about $4K to have the fixture sent back to the factory in addition to overnight both ways shipping costs for a fixture that takes at least three people to lift. Seems the very optically pure reflector to the follow spot in taking that dump off a Geni lift had gone off axis if not the entire fixture had warped. Luckily Lycian provided a loaner for the show the destroyed one was needed for. As concept, if the reflector has fallen out of ellipsoidal cone shape, it could also be a cause of that brown ring I theorize given my failed attempts to make that follow spot work in time for the next show it was needed for given it’s having taken a dump. So in the case of the 3.5Q5 above that had the brown ring I could not get rid of, it could have been a lens, could have been the fixture in having a warp or could be the reflector so far given adjusting it’s lamp seating had no end result. After that, in brown ring on the Leko I’m open to other ideas. I the case of the follow spot, I took it from dual hot spot to just brown ring so I did well had it absolutely needed to go out. That’s chasing and refining a bench focus once beyond hope. Flat field across the beam but only it’s outer hard edge was screwed up. Yep, wasted about six hours on this but learned a lot about bench focus and optics.




In lenses alone for my lights, I knew I had one that was really a 3.5Q6, what I did not know was that I really have two 3.5Q6's and one 3.5Q5.5. This is not a typo, in comparing lenses I have what’s clearly 3.5Q5 lenses, 3.5Q6 lenses and another size in between which won’t while installed in a Q5 lens train come to a hard edge beam. I expect over the years in not knowing that I had a second 3.5Q6 lens train it’s because it’s lenses were installed in the 3.5Q5 position thus would work but not come to a hard clean bench focus edge. Seven fixtures and I have already spent over $400.00 in new lenses shutters and other parts for them at this point. Lots of chipped lenses from snapping in the wee bit too sharp retaining ring over the years. Them retaining rings have been wire wheeled down to not so sharp. Than we get into the oil coating over the new shutters. I was bench focusing in my garage one night. Had to open the door once the fumes got too much. No idea of why new Leko shutters were coming with a oil film on them but it took about an hour to burn off given I had not thought of removing it than coating them in spray on graphite. Than of course it could have also been the amount vehicle left over from the spray on graphite coating I applied to all other moving parts. Chose not to wipe off the excess graphite as normal for me on these. Combination of the two in both oil on the shutters and excess vehicle to the spray on graphite, it took about an hour for each fixture to stop smoking in a big way. Than one gets to re-clean the fixture...

In addition to this, of the seven fixtures I am working on, one clearly has a 3.5Q6 lens train. Two have a 3.5Q5 lens train that I believe is no longer available. The other four have 3.5Q6 lens trains with dual dimples in them so as to mount either a 3.5Q5 and 3.5Q6 position for their use. I find such things interesting to note. Details like this also help me age fixtures. Three of my fixtures are older than the other four.


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## mbandgeek (May 12, 2006)

one thing that i know is that you set the instrument down on a table, have it shoot out a beam onto a cyc, and you try to make an evenly toned circle. This summer I am going to learn from a local theater to learn techniques how to achieve this. i am also hoping to learn how to properly clean a lighting instrument.


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## derekleffew (Jul 1, 2008)

mbandgeek said:


> One thing that i know is that you set the instrument down on a table, have it shoot out a beam onto a cyc...


Even though it's called bench focus, I would not recommend laying the fixture down on a table. If possible, in a theatre I would fly in the First Electric to +6'-0" and focus onto the cyc. If no electric or cyc is available, I would mount the fixture on a sidearm on a boom and point at a white wall. Local control of dimming is handy, as one does not need to run the lamp at full for the entire 10-15 minutes it may take for some fixtures. Most should take under three.


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## NHSTechCrew (Sep 21, 2011)

This stuff is gold. I am planning on going through our inventory. I am sure they have not been cleaned or benched for over 10 years. 

Thanks
-Patrick


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