Looks like what we've heard called 'zipper tracks'. We've seen them on 16 pop shots where there was very slight movement (it doesn't take much) during the exposure. They're most noticable where at the edges of highlights. Building shake - if you're not on the ground floor, trucks going by even if you are on ground level can cause enough movement to create the artifacts your seeing.
We shoot with an eyelike back, so I'm not familiar with the Sinar or its software. I would imagine that the sinar back has a provision for zeroing the piezo motor - cycling it once to ensure that it is in it's proper starting point - this is a good idea every time you use 16 shot capture. If we're doing a series of shots using 16 shot, we often will calibrate the piezo movement before the first shot is set up. It's a lot more involved that just zeroing the motor, but, with practice, it doesn't take too much time. It all helps eliminate the artifacts you're seeing, but it can't overcome even very slight camera movement during exposure. Afterall, the motor is moving the chip in increments of one-half a pixel left to right and up and down. That's roughly the equivalent of 160th the diameter of a human hair. It doesn't take a lot of movement to get those kind of dimensions out of registration.
We're on the ground floor, concrete slab floors, camera mounted to a sturdy studio stand, and we've seen them happen if someone walks too close to the set during the series of pops. Now we just keep all hands well away from the set while the exposure is underway.
aitor Pe�a Incl�n wrote:
Hi,
You could see it here.
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-- Jeff Smith
Smith/Walker Design and Photography
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