#19. "RE: If not Lubricant…then what?" In response to In response to 16 Thu 22-Dec-11 11:38 PM by elec164
>One of the reasons oil is not likely the cause is the range of >spot size. None are large which would be expected if some >mechanical throwing was involved, the spot size is constrained >to a range of limited variability.
But the spots do vary in size and I think my enhanced (equalized and sharpened) example is not an accurate representation of the spots. I stopped being lazy and setup my two flash units on stands to properly expose the white paper instead of processing it to make it look better. This is a 100% crop of the bottom right corner (should be upper right looking into the mirror box from the front).
As you see the spots do vary in size and some are even irregular and not round. You make a good point in that I have a hard time wrapping my mind around how the mirror mechanism could sling oil back at the sensor. I provided the crop straight from the camera so you can view as you wish. I did a threshold adjustment on it and it really shows the variation in size and shape well.
But then I found this discussion over at DPreview which I believe you took part in Stan. Jostian who made the last post (when I looked) stated that Nikon repaired his D7000 stipulating that the mirror drive motor in early production units was the cause. Under certain conditions lube would push past the seals in the motor and spew lube. Again the oil spots shown by Canon and others are clear in the center and darker rings where these are blurry spots. And that’s why I state lubricant and not oil.
It would be nice to verify the statement by Jostian in that DPreview thread, for if that’s the case and the drive motor is pushing out lube, it will eventually fail out of warranty and be a costly repair I would think. If I can document it now, even though the camera is over one year, they might replace it for free. Assuming that is accurate and I have one of those early production cameras (I did purchase in 11/2010).
Edited to add:
Stan, I know it’s probably prohibited by Forum rules to post an illustration from one of the Tech manuals. But can you verify that there is such a mirror drive motor, where it would be located and if the armature shaft is in such a location that lubricant leaking from a seal could spin off the shaft toward the sensor. I know I said I had trouble wrapping my mind around the mirror mechanism itself, but I could see lubricant flipping off a rotating shaft if that’s the case. And bearing lubricant for a motor would be more opaque than precision oil used on a mechanism. Just curious.