# Source Four Gobo Size?



## rochem

Okay, I feel kinda stupid asking this question, but is the best choice of Gobo size for use in a S4 (standard, not Jr)? I'm specing gobos for an upcoming show, and the venue has more than enough template holders of both sizes. I know that either A or B will work, but is one generally preferred over the other? Considering that the aperture of a S4 is 3" wide, I would guess that an A size pattern would have the best coverage, but I'm not sure.


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## Sean

rochem said:


> Okay, I feel kinda stupid asking this question, but is the best choice of Gobo size for use in a S4 (standard, not Jr)? I'm specing gobos for an upcoming show, and the venue has more than enough template holders of both sizes. I know that either A or B will work, but is one generally preferred over the other? Considering that the aperture of a S4 is 3" wide, I would guess that an A size pattern would have the best coverage, but I'm not sure.



A

Your guess is correct: you'll get more light/image area out of an A-size template.

--Sean


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## rochem

Sean said:


> A
> 
> Your guess is correct: you'll get more light/image area out of an A-size template.
> 
> --Sean



Thanks, that's what I thought. Two follow-up questions: I know I've had to cut gobos to get them to fit before, but I'm honestly not sure what size they were. Rosco Gobos - Gobo Holders tells me that A-size temps must be trimmed to fit into the gobo slot. Is that true? It sounds like that would be kind of annoying to do for every gobo. 

And also: if A-size temps provide more light and coverage, then why are B-size temps often used in S4s? What does a B-size temp give you that an A-size cant?


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## zuixro

rochem said:


> Thanks, that's what I thought. Two follow-up questions: I know I've had to cut gobos to get them to fit before, but I'm honestly not sure what size they were. Rosco Gobos - Gobo Holders tells me that A-size temps must be trimmed to fit into the gobo slot. Is that true? It sounds like that would be kind of annoying to do for every gobo.



It may be annoying, but DO NOT just fold it over. I had a S4 that someone had folded the gobo over the edge of the holder and crammed it in there. We didn't notice until it was already hung 18 feet up on the grid. I had to yank it out while standing at the top of an A-Frame extension ladder. I sliced my thumb open (Gaff tape is sterile right?).


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## derekleffew

rochem said:


> ... And also: if A-size temps provide more light and coverage, then why are B-size temps often used in S4s? What does a B-size temp give you that an A-size cant?


The smaller image area of the B-size allows for a more evenness of field, and the ability for sharp focus across the entire image, thus B-size is preferred for logos and text. 

For breakups, shapes, non-realistic images, and where the image is not desired to be in sharp focus anyway, use A-size.


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## Sean

rochem said:


> Thanks, that's what I thought. Two follow-up questions: I know I've had to cut gobos to get them to fit before, but I'm honestly not sure what size they were. Rosco Gobos - Gobo Holders tells me that A-size temps must be trimmed to fit into the gobo slot. Is that true? It sounds like that would be kind of annoying to do for every gobo.
> 
> And also: if A-size temps provide more light and coverage, then why are B-size temps often used in S4s? What does a B-size temp give you that an A-size cant?



Yep, it's a pain: Rosco and GAM, are you listening??

Derek already partially answered your question: The main reason I've found that so many B-size templates are used is that before the S4 pretty much all the ellipsoidals in use used B size templates. When the S4 came out people wanted to continue to use the stock of templates they already owned.

Some places insisted on using ONLY B size for quite a while. Seems like it's only been maybe the past 5-7 years that "A" really has become the default.

My $.02

--Sean


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## xander

I think the two main reasons have been covered. But, I would like to elaborate on the second one a bit more. B-size were often used in S4s because they were already in stock, but it is also quite common practice today to still buy B-size if your inventory still contains older equipment that can't use A-size so that your gobo inventory can be utilized by all of your ERSs.


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## SteveB

B size is also used in the Altman Shakespeare, which means as well, the Altman 360Q, as well as Altman 1K ellipsoidal series and Altman 4.5" zoom series. Thus if you run into a house that uses these fixtures (like mine), B size will fit every fixture. 

As a result, I only order and stock B sized gobo's and holders. If you come to our house and want A size, bring them, plus the holders.

Steve B.


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## rochem

SteveB said:


> B size is also used in the Altman Shakespeare, which means as well, the Altman 360Q, as well as Altman 1K ellipsoidal series and Altman 4.5" zoom series. Thus if you run into a house that uses these fixtures (like mine), B size will fit every fixture.



So this begs the opposite question: why are A-size gobos around? Since all the Altman fixtures accept B size anyways, the only reason I can see for continuing A size gobos is for use in Source Fours - but if you have to cut the A size to get them to fit anyways, why not just change the measurements of A size gobos to better fit in a S4? Or why did ETC not originally design the S4 to accept an A size gobo without any cutting needed?


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## xander

Anyone feel free to correct me if I am wrong...
The fact that the gobo needs to be cut is not the fault of ETC, it is the gobo manufacturers. It is the inside diameter or image size that matters, the outside edge can be any size you want and then trimmed to fit an instrument. I assume that A-size exists because ETC designed the Source4 to take an 75mm image size. But because the B-size is just a little bit smaller, they were like, "hey we can make a template holder to hold B-size so that the user doesn't have to buy all new templates." Why the Source4 was designed to take 75mm size? I have no idea. Probably has something to do with optics.


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## icewolf08

In some respects you are kinda wrong. The A-Size gobo was not designed for the source four, the source four is just capable of utilizing an A-size gobo. There are many other fixtures that use A-size gobos and have for a while. So, it is not the fault of the gobo manufacturer that you have to trim an A-size template to put in in a source four holder because those templates probably fit in some other type of unit without modification.


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## rochem

icewolf08 said:


> In some respects you are kinda wrong. The A-Size gobo was not designed for the source four, the source four is just capable of utilizing an A-size gobo. There are many other fixtures that use A-size gobos and have for a while. So, it is not the fault of the gobo manufacturer that you have to trim an A-size template to put in in a source four holder because those templates probably fit in some other type of unit without modification.



So then why were the original Source Fours designed with a "nonstandard" pattern size? I admittedly don't know much about lighting instrument design, but is there some reason why the Source Four couldn't have been designed to fit either A or B size gobos, rather than basically being halfway between two sizes?


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## derekleffew

rochem said:


> ...but is there some reason why the Source Four couldn't have been designed to fit either A or B size gobos, rather than basically being halfway between two sizes?


The SourceFour CAN take either size. What it can't do, because of the laws of optics, is focus uniformly across the entire image of the A size, as even the improved filament design of the HPL lamp is not a "theoretical point source."

As I recall, until the SourceFour, I never had to worry about this A or B size crap. One either bought standard full-size gobos or small gobos for 3 1/2" Lekos. ALL of them needed to be trimmed to fit in the holder. Great American Market (now GAM) and Theatre Magic (now Theatre FX?) were the only suppliers. Then in the late 1980s Rosco began selling the DHA line of gobos, which being round were revolutionary, but still needed to be trimmed to fit in most holders.

*Someone*, and I'm not sure if it's the manufacturers, dealers, designers, or end users, is making the whole thing much more complicated than it needs to be.
/rant off


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## L00p23

I've been having these questions too. As for the gobo fitting into an S4, I've found that Apollo gobos are great in that respect. They only have a thin strip of metal around the outer edge of the image. they fit perfectly in the holder without the need to trim anything.


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## Kelite

In my simple opinion (and obviously Derek is right on the money here), A size images are great for maximizing total light output for break-ups. Conversely, when a corporate logo needs to be crisp across the entire image area, the smaller image area of the B size gobo allows a crisper read. There are many gobos created with only 75-85% available image area to futher define corporate logos.


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## rabvicar

*gobo size A or B..that is the question*

Recently I have come across the debate over the best size gobo image for source 4 instruments. As usual a corporate client wanted an 8' projection of the company logo. I was handed a standard apollo glass gobo size B, the standard size. Of course it didn't appear the same as printed sign or that perfect pantone presentation. The image was of course flared on the outside edges as they all want to do, even after the doughnut is in, with the lenses clean and the instrument bench focused. we have all come to expect this to happen because the image is large enough to fall out of the beam width,or more tward the edges of the convex lens. Then I was look for a solution to this problem and noticed a side note from ETC that read "because the apeture is 3" a size A gobo is recomended". Does this really help? Not having any A size gobos in my files I made my own to see but wasn' impressed. Is there a solution to this issue?


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## JChenault

*Re: gobo size A or B..that is the question*

A B size gobo ( all things being equal) gives a better image definition than an A size gobo ( it's area of pattern is smaller). An A size gobo gives better coverage at some loss of sharpness.

If you want some sharp projections with ETC you should move to the enhanced lens tube. Somewhat spendy, but the optics are much better than a standard unit.


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## Kelite

*Re: gobo size A or B..that is the question*


JChenault said:


> A B size gobo ( all things being equal) gives a better image definition than an A size gobo ( it's area of pattern is smaller). An A size gobo gives better coverage at some loss of sharpness.
> 
> If you want some sharp projections with ETC you should move to the enhanced lens tube. Somewhat spendy, but the optics are much better than a standard unit.





Amen on both accounts, brother JChenault.


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## rabvicar

*Re: gobo size A or B..that is the question*

cool thanks, that will help put this thing to bed.


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## Pachinko

*Gobo too big for the holder?*

Hi!

I recently bought some gobo and gobo holders for my school theatre. I am sure I ordered size A gobos and holders. But, there seems to be a bit of an issue. When I put the gobo into the holder, there is a little bit of overhang...about .5cm. When I go to put the holder with the gobo in it into our Source 4s, it wont go in. It gets stuck around where the gobo starts..

Am I able to cut the gobo down? Have I ordered the wrong size? Do source 4s only take size B?

Thanks for your help! 
I have attached a photo of the gobo in the holder for reference.


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## Toffee

*Re: Gobo too big for the holder?*

You can just cut that small over hang off, just when you do be careful to make sure you have enough for it to still sit inside the holder properly. Check out this post out for more info.


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## techieman33

*Re: Gobo too big for the holder?*

Just trim the gobo down.


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## derekleffew

*Re: Gobo too big for the holder?*

From Rosco - Gobos under "13610 Sandwich-Style Pattern Holder": 

> For use in:
> ETC Source Four, Source Four Zoom
> (Note: A size gobos are 100mm wide and will require trimming in order to fit into the static gobo slot of the Source Four)


The holder is 3-11/16" (~94mm) and the template is (~4") 100mm. Gobos trim easily with standard scissors. [Just don't use the Costume Shop's shears--or they'll needle you for it.]

Pachinko, I notice your, or someone else's, fingerprints on the pattern. With today's cooler gate temperatures, not as big a deal as it used to be, but still something to be avoided if possible.


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## DaMenaCe

zuixro said:


> It may be annoying, but DO NOT just fold it over. I had a S4 that someone had folded the gobo over the edge of the holder and crammed it in there. We didn't notice until it was already hung 18 feet up on the grid. I had to yank it out while standing at the top of an A-Frame extension ladder. I sliced my thumb open (Gaff tape is sterile right?).




How does one cut/trim the gobo?? SOrry i am complete noob at source4 fixtures..


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## Les

DaMenaCe said:


> How does one cut/trim the gobo?? SOrry i am complete noob at source4 fixtures..



I've always just used scissors, but use some that are already on their way out or specifically for that. Wouldn't want to dull your office/gel cutting pair. You can also use aviation shears (tin snips).


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## gafftapegreenia

Ship turned me on to using those stout electricians scissors the datacomm guys use. Klein and Ideal make some very suitable pairs. They are dang sharp!


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