Originally posted by awscreo huh, so I went out and shot a sequence - DFA 28-15, 28mm at f6.3, starting at 1/5 all the way to 1/250, with 3 exposures for each stop.
Weird things happened. from 1/5 to 1/25 image is razor sharp. from 1/30 to 1/80 it's softens up. 1/100 to 1/160 is very soft. At 1/200 image starts to become sharp again, and at 1/250 image is razor sharp again.
So what the hell lol. SR works for very slow shutter speeds, but doesn't for ones that should be sharp logically? Is shutter shock affecting images from 1/30 to 1/200??? that's just crazy! Is my unit faulty? I'm paranoid now.
Just to be sure I'll probably do a set with another lens, probably my 50 1.8 because i don't remember getting results like that with that lens in the past.
I'm thinking maybe to send it in to tune up to Pentax if this is outside of the spec..
Full res jpegs from sequence are below (still being uploaded as of now):
Update your browser to use Google Drive - Drive Help Although it seems weird, what you are seeing makes complete sense if you think about what's happening inside the camera.
When the exposure begins, the first set of curtain blades fly open and hit their end of travel with a tiny bang that is just a bit too fast for the SR system to compensate. The image shakes for just a tiny fraction of a second.
For a slow shutter speed, the shutter shock is still there in the image but the fraction of the image's light that was collected during the shock period is small compared to the amount of light collected during the rest of the shutter's opening time. The longer the shutter is open, the less the relative contribution of the perturbed image in the final result.
If the shutter speed is near or faster than flash sync speed, the shock created by the start of the closing second curtain actually acts in the opposite direction of the shock created when the first curtain hits the end of travel. Thus, the total shock in the camera is lower.