Standard definition and any HD modes that end in i for NTSC is
interlaced at 29.9Hz, so it scans every second line on the screen
slightly under 30 times per second, but hits every line slightly under
60 times a second. Progressive scan HDTV in NTSC scans the full screen
at 29.97Hz. Contrary to popular belief it is not timed off of the power
frequency, however it was back in the days of B&W only TV (The slight
change occured when Colour TV was introduced to the standard, the
difference is the reference clock for the colour encoding)
-Adam
Jack Davis wrote:
Seem like someone told me that the TV electron gun operates at 60
cycles per second.
Not at all sure this is right, but it MAY make a one way sweep of the
screen every 1/60 of a sec.
Someone else claimed the gun made a complete picture every 1/30 of a
sec. That COULD mean one two way sweep.
IOW, I don't know either.
HD and Plasma notwithstanding.
Jack
--- William Robb <[EMAIL PROTECTED]> wrote:
----- Original Message -----
From: "Jack Davis"
Subject: Digital Shutter Speed Tester
I freely check the accuracy of shutter speeds with my own tester. It
has caused me to send bodies to Pentax for repair a couple times.
Obviously, I must remove the lens and open the back to allow the
test
beam access to the shutter. How could a DSLR shutter be tested?
I used to know how to test shutter speeds using a picture taken of a
television screen, but I forget how. Something about counting the
distance
between scan lines or some such.
Perhaps this will remind someone of how to do it.
William Robb
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