Design Gobos with 70-Degree S4

[jmac]

I have used gobos with 26, 36, 50 degree S4's. But never with a 70-degree S4..

Due to short throw of about 10 feet, even the 50-degree beam is too small for the application.

Are there any issues projecting gobos with a 70-degree fixture..? Just never tried and wanted to check before we rent the fixtures. I know the 70-degree lens tube does not have much travel in the S4..

(We don't need a super sharp focus, as we are using for a general soft breakup). Thanks!..

 

[timhughes]

You can get a sharp focus with 70 and 90 degree barrels. There are two things you should consider: If you are projecting at an angle to the floor or set, you will not get a flat field of focus. Meaning you can either focus sharp the close edge of the beam, or the far edge, or split the difference somewhere in the middle. Also the inverse square law dictates that at the close edge of the gobo pattern will be smaller and brighter than at the far edge. The hot spot of the beam may need to be compensated by playing with those knobs on the lamp cap. There are many creative and practical ways to use wide angle lenses. If you've never played around with one, I recommend you rent one for the weekend just for the experience.
It'll be more fun and cheaper than going to the movies lol.

If you are projecting a custom gobo, such as a company logo, you should try to hang the light on axis with the image to prevent skewing and distorting it. Also, when you design such a gobo, try to keep the image a bit smaller than that of a B size gobo so the edges don't get blurred. Cheers!

 

[NevilleLighting]

...what Tim said. The 70 and 90 degree lenses really do well with less distortion than you might expect. Perhaps a touch more difficult to get en even pattern edge across the whole field but I'm always impressed. Since you're going for soft focus you shouldn't have a lot os issues.

 

[JChenault]

(We don't need a super sharp focus, as we are using for a general soft breakup). Thanks!..

Don't forget. One issue with soft focus using the lens tube is color fringing. Another way to get a soft focus is to focus sharply then take a slight frost ( Roscon132 comes to mind. Gam had a similar product but I'm not sure if it is still carried. Not sure what the Apollo equivalent would. )