Conventional Fixtures Using a Gobo in a Source 4 70 degree

[DistrictDesigner]

Wondering how sharp a cityscape Steel Gobo can look on an interior wall in a Source 4 70 degree from a grid 22 feet high at a throw distance of about 45-50 feet? Or should I use a 50 degree? Thanks for the input.

 

[jglodeklights]

While not part of their Enhanced Definition Lens Tube lineup, technically the 70, 90, and 14 degree lens tubes are inherently enhanced so they should provide better quality than standard lens tubes. The issue here is that at that throw distance you're going to be projecting a huge image- about 60' in diameter. Beamwright tells me that even at 750W standard life you're only going to be getting 9 footcandles at center. It's going to be big and dim and dimmer yet if you use a 575W or extended life lamp. Maybe that is fine for your purpose, maybe not. This is also going to test the resolving power of the 70degree lens since the 70 and 90 are optimized for shorter throw projection. Their datasheets don't actually give photometric numbers for more than 20' as that is kind of the maximum distance they are designed to work at. Generally in a situation like this you're better off using multiple fixtures and distributing the work and making art with possibly different gobos in each (like selecting ones where you can cut out sections that don't match to line them up with each other).

 

[derekleffew]

Wondering how sharp a cityscape Steel Gobo can look ...

I don't think sharpness will be your greatest concern. As said above, intensity is the primary factor, as well as 70 & 90° are known for their distortion, specifically pin cushion effect, where straight lines appear curved.

Rather than have one fixture do the entire skyline, i'd break it up into at least three fixtures, each doing its own linear portion.

 

[Kelite]

I'll agree with @derekleffew as the wider the beam, the less crisp and sharp the projection. If clarity is of importance, splitting the total projection into smaller areas will not only provide a cleaner gobo image, but the brightness will certainly benefit as well.

Thank you-

 

[DistrictDesigner]

I don't think sharpness will be your greatest concern. As said above, intensity is the primary factor, as well as 70 & 90° are known for their distortion, specifically pin cushion effect, where straight lines appear curved.

Rather than have one fixture do the entire skyline, i'd break it up into at least three fixtures, each doing its own linear portion.

That's a great idea! So if I break it up and move it closer to the wall, I can still cover with a sharper image. How about if I do that with two 50 degree instruments from 25'? I can still cover about 50' of brick wall. I appreciate your replies.

 

[seanandkate]

Two 50deg would cover 50' of wall with 57 fc.

Here's an ETC app you might find useful as you are playing with scenarios.