(Leaked?) 5D mkII Test Shots at ISO 25,600

[alan_bryant1]

<p>There are two shutters, generally called first curtain and second curtain. The first curtain opens to expose the

sensor, the second curtain closes to cover it.</p>

 

<p>The interesting part is, high shutter speeds can be achieved by overlapping these two operations. That is, the

second curtain begins closing <i>before</i> the first curtain has finished opening. For fast exposures like 1/4000, the

second curtain is only just <i>right behind</i> the first. The gap between them is very small. And every portion of the

sensor recieves a 1/4000 second exposure, even though the entire exposure as a whole took much longer than

1/4000 to occur.</p>

 

<p>The problem with a flash is, the whole frame has to be exposed when the flash fires -- you can't have either

curtain covering the sensor. So the flash sync shutter speed is much slower than the fastest shutter speed

achievable.</p>

 

<p>When I figured my 10.7 mph, I was leaving no time for the flash to fire. Mark U suggests 1.6ms would be required

for a full power flash -- that would imply that 1/625 is the fastest flash sync shutter speed that can be achieved at all,

no matter how fast the shutters move. As you approach 1/625 the required speed of the shutter blades becomes very

very fast. Passing 1/300 enters a world of diminishing returns -- doubling the shutter travel speed only slightly

improves the flash sync speed.</p>

[mark u]

http://www.photozone.de/standard-flash-sync

 

http://www.photozone.de/hi-speed-flash-sync (also shows how high shutter speeds work)

 

http://www.eosdoc.com/manuals?q=Flash+Curves (how long do curtains need to be open for X sync)

[scott_ferris]

I love it when these things go off topic sometimes!

 

Anyway, my 1D syncs at 1/500, how? Oh, I understand my chip is smaller than the full sized one being talked about but it is still pretty fast. It does it by useing a CCD rather than the "better" CMOS, the shutter is open longer than 1/500 but the sensor is only sensitive for that, kinda cool huh, so don't see why they couldn't sync CCD's much faster, well they probably do in some other imaging areas, but progress and the perceived advantages of CMOS chips over CCD's have left you guys all struggling. Silly thing is although I have a good flash set up I hardly use it!