Scrim?
 

What is a scrim?

It's a wire mesh that can be mounted onto a light (usually behind the barndoors) to reduce light output. They come in various grades and also as a half, which covers only half the light, so you get full output in one half of the beam and a reduced light level in the other half.

so if it just reduces the output, what is the difference between a scrim and regular diffusion?

It doesn't diffuse, it leaves the light hard. You have the full focusing and barn-door cutting capabilities the light originally had.

The scrims are made of wire mesh, therefore they can be very close or touching the lens and they will never catch fire. They're also very quick to work with, but be sure to bring your gloves because they can get hot.

Generally, a professional rig of a fresnel will include full, double, half-full and half-double scrims, greatly increasing the versatility of the light. And you can still use diffusion if you want it.

And most of all, don't forget a scrim bag, they are very handy for hanging the scrims off of the light stand so that they are handy and right there for you to use.

Dan

Would a DIY approach using window screens work, assuming they aren't the cheap-o plastic type?

You may also want to have a two doubles.

When the fixture has no scrims-"steel", it's "clean".
Drop some steel- Add a scrim, sometimes you'll have an idea of what to use. If not, ask the Gaffer.
When you drop the scrim in, say what it is you are putting in, example:"Single in."

Double - Double scrim
Triple - Single + Double
Home Run - 2 Doubles
Grand Slam - 2 Doubles, 1 Single

DIY, not so much. You can get skewered by the loose wires sticking out. Not safe. The single cuts exposure bout half a stop. Double about a full stop. They have a color coded ring to prevent the wires from unraveling and pricking you. Single us green, double is red. Some manufacturers have alternating color and no color for the halves.

Thanks a lot for all the help guys.

So if it reduces exposure by half stops and stops, but yet doesnt diffuse, whats the difference between scrims and ND gels, other than durability?

The differences between the two are resistance to heat/melting and ease of use. With ND gels, they have to be clipped to the barndoors (which limits the doors' ease of use) or flown on a frame (sometimes requiring another stand). A scrim just pops into the light in no time, that's it. So, you're controlling the light without really adding anything. When all is said and done with scrims, you've got a light of the same dimensions and maneuverability as before with no noisy gels hanging off of the doors.

Hope that helped.

~~Dave

The window screen material on all of the windows on my house would go up in flames in about :30 in front of a 1k. I don't think most of them use actual wire mesh anymore, it's coated and sort of Nylon looking in most cases.

Why make scrims? They are one of the cheaper parts of lighting gear and do a really great job.

Dan