Source 4 donut aperture size

[Mr Steve]

Hi,

 

I understand that a donut is used to help sharpen a gobo in a profile. However, what effect does the aperture size have? For example a Source 4 donut has a centre hole option of 2 1/2", or 3 3/16". Will the smaller aperture lead to sharper image but further decreased brightness in comparison to the 3 3/16" one?

[andy_s]

I used to use donuts on older profiles, (sils / cantatas etc), found less of a need on S4s... as I remember it is smaller = sharper, but the pay off is a loss of light output. one way of experimenting thing is to invest in some black cinefoil, cut it to colour frame size, and make your own hole. start small and make bigger until you get an acceptable balance of output / sharpness.

[J Pearce]

For brief experiments card is fine, then once you have a good size cut from cinefoil. Saves wasting the expensive stuff.

[Mr Steve]

Thanks folks. Have some cinefoil so will have a look time permitting.