Having Some Trouble Understanding...


Active Member
Hi Everyone,

I have a quick question: I have a bunch of fresnels hanging that I want to be able to use in the next production that I'm designing. I was trying to figure out the size of the beam and how bright it would be at certain distances, but I was having some trouble deciphering what everything in the photometrics means.

Here is the link:
Its on the second page. (I'm not sure which size we have {i have to check}, but that doesn't matter to me, since I just need to know what everything represents)

Thanks in advance


CB Mods
Premium Member
It'll be pretty easy to tell which size you have just measure how tall it is.

Here's the quick and dirty on the spec sheet. Where it says Fresnelite 6"spot means when the Fresnel is in spot or adjusted all the way back. Looking at the graph Ther first bit distance is how far away from what you're shooting, Beam is how big the circle of light will be on the ground, and illum is the measurment in FC or how bright it will be.

The next chart down is the same in flood, or when its adjust all the way forward.

Wait...reading it further I guess the focus is a adjustable arm on the back of the light...there'll be a little graph on it to tell you if you are in spot or flood or somewhere between.

Anyway....if I'm shooting from say 13 feet away with the 6" Fres and I want the light to flood everywhere... the light is going to be about 14' big...this is a little bit of guess work because I'm looking at how big the light would be at 10 feet and at 15 feet and finding the number in the middle


Active Member
Yep, Grog's got it. Those fixtures are adjustable. You can flood them all the way in or out. There is usually what is known as a Mulitplying factor that is available for fixtures that lets you figure this out, but in a situation like this, you can't really do it. Same thing with a zoom. It's adjustable between a certain degree measurement and you kinda have to guess and play with it some. You know what the max and the min are, as long as the size of field you want is between those, then you are ok.

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