Re: Flicker?

Michael Wakefield (mwakefie@KEENE.EDU)
Tue, 17 Jan 1995 16:10:42 -0500


On Tue, 17 Jan 1995, Craig Miller wrote:

>
> OK, here is why zooming can help/hinder the scan rate problem. Let's assume
> that your camera is in the US, and takes approximately 65 miliseconds to
> scan a single line (as it does in NTSC), and what you are shooting takes 70
> milisecs to scan on a time line this would look like this:
>
> Real Time
> cam
> |---------------->|
> PC
> |------------------->|
>
>
> If by zooming way out on the PC screen you change the apparent scan rate of
> the PC screen.
>
> Zoom way out
> cam
> |---------------->|
> PC
> |-------->|
>
> By zooming to the 'magic' point you can get the apparent scan rate to be
> close to the camera's scan rate.
>
> Zoom to the magic point
> cam
> |---------------->|
> PC
> |-------------->|
>

Yep, Craig, it makes sense when you look at the skeeeematic diagram. In
the case of a computer display, it seems more likely that it would work
because you reached some NTSC scan rate evenly divisible by the display
rate. This differentiates "flicker" from seeing the "bar" caused by
catching the vertical blanking interval "in the act", so to speak.

Thanks for the reply...

==Mike