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| p.1 #17 · Reason why a camera won't shoot faster than 1/3000? |
For a focal plane shutter, at shutter speeds faster than the sync speed, the duration of exposure generally is not determined by the rate of shutter curtain's movement, but rather, by the width of the gap between the first and second curtains. This is an important principle to remember. A faster curtain speed only facilitates a faster sync speed, but no DSLR focal plane shutters have a sync speed as fast as 1/3000 s. In actuality, these shutters typically take around 1/250 - 1/500 s to travel the 24mm vertical distance.
With this in mind, what exactly is meant by "it just won't capture an image?" Does that mean that no file is generated at all? Or does that mean a file is written to the card by the camera, but it is black? If the former, there is some defect other than (and perhaps in addition to) the shutter mechanism. If the latter, then see if the resulting file contains sensor noise. If not--the file is pure black--then again, there is some other defect. If there is read noise, then shutter failure is the likely culprit. For further supporting evidence, check for the possibility of exposure inaccuracies by shooting a uniformly-lit subject (e.g. clear blue sky) at shutter speeds approaching 1/3000 s, then compare with an average of baseline exposures taken below the sync speed of the shutter. If the curtain timing is off, this should manifest as exposure error.
If no exposure discrepancy is discovered, that should not be construed as proper operation of the shutter.
Finally, one should double-check whether or not the shutter even opens at all at high speed. This can be done by engaging mirror lock-up, removing the lens, and listening for the shutter sound in addition to watching the shutter for any sign of movement.