Source 4 - Large Gobo projection

[beardedbil]

Hi All,

Please forgive me if this question shows my naiveté I just have never projected a Gobo this large before. A client needs a full color glass Gobo of his logo to be projected 20' in diameter. I was thinking of using a Source 4 with 90 degree lens so we can get that 20' projection from only about a 12' throw. My question is I have been looking at both Source 4 750 watt units as well as the Source 4 HID 150 watt units. According to their cut-sheet they appear to be very close in specs and light output. Would anyone recommend one over the other? I understand the HID is about double the price of the original Source 4, the bulb will last longer, and draw less power, but is there any other reasons to pick the more expensive HID over the 750 watt? Any information would be great!

Thanks in advance.
Best,
Bill

 

[bishopthomas]

The HID will be a different color temperature which may make the gobo's colors either better or (more likely) worse. I don't have my chart in front of me, but if you've done the calculation and 90 deg is what you need to make a 12' throw work for a 20' image then you're all set. Is this a one time event? And installation? Are you buying a fixture or renting?

 

[beardedbil]

Thanks for the advice, we will be buying the fixture and gobo and then selling to our client. We will also provide the installation. Our biggest problem is we will be projecting on the outside of a tent and the tent curves at the top so we will probably have some key-stoning problems. I know you can get this corrected in the glass if you know your angel etc, but our client just wont have this info until we are on-site. This project will run for about a month and a half. It will be outside so I will have to tell them to bring the unit in nightly.

 

[derekleffew]

Other considerations:
Most clients are rather picky about how their logo is displayed. Cut, color, clarity, etc.
The 90° lens is particularly susceptible to the pin cushion effect. Straight lines will appear curved.
Unless the luminaire is perfectly perpendicular to the projection surface, you'll have a keystone effect. This can be countered in the making of the custom gobo, but the maker will need to know the exact projection geometry.
.

 

[TJCornish]

I've always been told the wider the fixture, the worse for gobo projection. 90° seems scary. I've had good luck with 36° fixtures. The EDLT tubes help.

One other option may be using a video projector - most nowadays have keystone correction in a couple axis, though depending on your brightness requirements, may be cost prohibitive.

 

[beardedbil]

The reason we need a 90 degree lens is because we can't be that far from the tent for power etc... so to get the clients requested 20' projection (at a reasonable brightness) it seems the only way to go. Also they will be washing the tent with uplighting from LEDs. I did look at video projectors and the cost was just too high to get any amount of brightness. Do you think the 90 degree lens will be so bad that it will not be usable for Gobo? Thanks for everyones advice.

I could probably go to a 70 degree lens at about a 18-19ft throw.

 

[TJCornish]

Here's the calculator:
KnowledgeBase: Spreadsheet Calculator for Gobo Projected Image Size - Electronic Theatre Controls

Looks like you need to be pretty wide to make it work.

Not sure what to tell you other than to not promise any specific image quality to the client until you've tried it.