Hi all,
>> One way to get a ball park idea on curtain speeds being "atleast close" is
>> to open camera back, set to 1/1000 manual, remove lens, hold camera up in
>> front of a television, look through shutter as you fire it. If curtain
>> speeds are close you should see a diagonal band of light maybe 1/8" wide.
>Well this is what I call a useful hint.
>I didn't know about this trick.
>It works on mine, although diagonal band is not always at the same place,
The position of the band depends on the timing of the cathodic ray scan on
the TV screen. It usually takes at least two or three shots to check the
height of the band.
The inclination of the band depends on the sync speed -- the faster the
sync, the more horizontal the band gets. A *trapezoidal* band is definitely
a bad thing (different curtain speeds)
>and I cannot tell if it's 1/8" wide.
What I do is to compare the height of the band with the full height of the
TV screen. In Europe, with the 50 Hz TV system, a full scan of the screen
takes about 1/60 (a little time is lost during 'flyback'), thus:
at 1/60, the whole screen looks illuminated, maybe with a thin dark band.
at 1/125, the band should be *half* the height of the screen.
at 1/250, " " " " *a quarter* of the height of the screen
...and so on (1/500 => 1/8 height, 1/1000 => 1/16 height, etc)
With the America's 60 Hz TV system, the band should be about 20% taller --
at 1/60 you'll probably see a thin *lighter* band.
A few things to note:
==Cameras with horizontal shutters (eg. most OMs) should be kept horizontal
('landscape' orientation), but those with vertical shutters (eg. OM-2000)
must be placed vertically ('portrait' orientation)
==It's best to do this with a proper TV signal, *not* from a VCR.
==With those modern, easier-to-the-eyes, dual-scan TV sets (100 Hz in
Europe, and I think 120 Hz in USA), you lose one checkable stop :-( full
screen at 1/125, half height at 1/250, etc.
>Sometimes its very well defined and
>thin, sometimes wider and less defined.
>IMHO, this is due to the TV CRT and not to the shutter.
Again, it depends on the TV picture and CRT characteristics. A bright,
contrasty image in a nomally lit room seems to work best.
Hope this helps,
...
Carlos J. Santisteban
<cjss@xxxxxxxxxxxxx>
<http://cjss.galeon.com>
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