[Tig] C-Reality/DSX gate aperture

[Dave Corbitt]

Rob,

An adjustable aperture was done to increase depth of field and 
improve flatness of focus across the film frame. A smaller lens 
aperture increases depth of field (but decreases signal to noise). On 
the C-Reality series of machines, the skid plate was slightly curved 
to keep the film from buckling, but the CRT screen was a flat 
surface. This optical plane mismatch could cause slight softening of 
focus on the top and bottom of the film frame. Increasing the depth 
of field could minimize that effect but the cost would be reduced 
light through the film which would mean a noise penalty.

When I was with ITK, we addressed this by specifying a curved 
faceplate CRT with a radius that exactly matched the skid plate so 
depth of field could be extremely small but the entire film frame 
would remain in focus all the time. We therefore could use a very 
large aperture lens to gather lots of light and not pay the depth of 
field penalty.

Disclaimer: Over the years, I've worked for Cintel, ITK, Thomas 
Electronics (they made the ITK CRT), and several post houses. I'm not 
on the payroll of any of them at the moment. I'm currently with 
FrontNICHE selling VUTRIX monitors.

Dave Corbitt
FrontNICHE
Summit, NJ

At 11:35 AM -0300 5/10/07, Rob Lingelbach wrote:
>
>Could someone advise me the reasoning behind having an iris on the
>C-Reality/DSX's 35mm and 16mm gates, and what the recommended settings
>are?  Why would one ever want to diminish the amount of light output
>from the tube?
>
thanks in advance.
Rob